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The prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC) are involved in the control of horizontal and vertical gaze, respectively. A previous study showed that PHN neurons exhibit depolarized or hyperpolarized responses to noradrenaline (NA). However, the adrenoceptor types that participate in NA-induced responses and the effects of NA on INC neurons have not yet been investigated. Furthermore, the relationship between NA-induced responses and neuron types defined by neurotransmitter phenotypes has not been determined. In this study, we investigated NA-induced current responses in PHN and INC neurons and the relationships between these responses and neuron types using whole cell recordings in wild-type and transgenic rat brainstem slices. Local application of NA to the cell soma induced slow inward (SI) and slow outward (SO) currents that were mainly mediated by α1 and α2 adrenoceptors, respectively. These current responses were observed in both PHN and INC neurons, although the proportion of INC neurons that responded to NA was low. Analyses of the distributions of the current responses revealed that in the PHN, all fluorescently identified inhibitory neurons exhibited SI currents, whereas glutamatergic and cholinergic neurons exhibited both SI and SO currents. In the INC, glutamatergic and inhibitory neurons preferentially exhibited SI and SO currents, respectively. When the PHN and INC neurons were characterized by their firing pattern, we found that the proportions of the currents depended on their firing pattern. These results suggest that various modes of noradrenergic modulation in horizontal and vertical neural integrators are dependent on neuron type. NEW & NOTEWORTHY Noradrenergic modulation of oculomotor neural integrators involved in gaze control has not been elucidated. Here, we report that noradrenaline (NA)-induced slow inward (SI) and outward (SO) currents are mediated mainly by α1 and α2 adrenoceptors in neurons that participate in horizontal and vertical gaze control. The NA-induced current responses differed depending on the neurotransmitter phenotype and firing pattern. These results suggest various modes of noradrenergic modulation in horizontal and vertical integrator neurons.

Sleep is an instinct behavior, and its significance and functions are still an enigma. It is expressed throughout one's life and its loss affects psycho-somatic and physiological processes. We had proposed that it might maintain a fundamental property of the neurons and the brain. In that context, it was shown that sleep, rapid eye movement sleep (REMS) in particular, by regulating noradrenaline (NA), maintains the brain excitability. It was also reported that sleep-loss affected memory, reaction time and decision-making ability among others. However, as there was lack of clarity on the cause-and-effect relationship as to how the sleep-loss could affect these basic behaviors, their association was questioned and it was difficult to propose a cure or at least ways and means to ameliorate the symptoms. Also, we wanted to conduct the studies in a simpler model system so that conducting future molecular studies might be easier. Hence, using zebrafish as a model we evaluated if sleep-loss affected the basic decision-making ability, a cognitive process and if the effect was induced by NA. Indeed, our findings confirmed that upon sleep-deprivation, the cognitive decision-making ability of the prey zebrafish was compromised to protect itself by running away from the reach of the exposed predator Tiger Oscar (TO) fish. Also, we observed that upon sleep-loss the axonal arborization of the prey zebrafish brain was reduced. Interestingly, the effects were prevented by prazosin (PRZ), an α1-adrenoceptor (AR) antagonist and when the zebrafish recovered from the lost sleep., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: RS17053 is classed as an α 1A -adrenoceptor selective antagonist., Objectives: We have examined its profile of action at all subtypes of α 1 -adrenoceptor., Methods: Noradrenaline (NA) evoked contractions of rat vas deferens involve α 1D -adrenoceptors in phasic contractions and α 1A -adrenoceptors in tonic contractions. Contractions of rat aorta to NA involve α 1D - and α 1B -adrenoceptors., Results: RS17053 (10 -5  M) shifted NA potency and virtually abolished tonic contractions to NA, with little or limited effect on phasic contractions. The α 1D -adrenoceptor antagonist BMY7378 (3 × 10 -7  M) significantly inhibited the remaining phasic component of the contractions, and the α 1A -adrenoceptor antagonist RS100329 (10 -7  M) inhibited further the residual tonic contraction. Hence, RS17053 shows high selectivity for α 1A -adrenoceptors over α 1D -adrenoceptors in rat vas deferens. However, RS17053 (10 -5  M) produced a large shift in the potency of NA in rat aorta, with a pK B of 6.82. Large shifts of NA potency in rat aorta involve α 1B -adrenoceptor blockade., Conclusion: Results in rat vas deferens demonstrate low potency of RS17053 at α 1D -adrenoceptors, but results from rat aorta can only be explained as demonstrating α 1B -adrenoceptor antagonism by RS17053. RS17053 may be a useful pharmacological tool when reclassified as a mainly α 1A - and to a lesser extent α 1B -adrenoceptor antagonist with little effect at α 1D -adrenoceptors., (© 2023 Société Française de Pharmacologie et de Thérapeutique. Published by John Wiley & Sons Ltd.)

Food restriction (FR) enhances sensitivity to cardiopulmonary reflexes and α1-adrenoreceptors in females in the presence of hypotension. However, the effect of FR on cardiopulmonary and vascular function in males is not well-understood. This study examines the effects of FR on cardiopulmonary, isolated arterial function, and potential underlying mechanisms. Male Sprague-Dawley (SD) rats were randomly divided into 3 groups and monitored for 5 weeks: (1) control (n = 30), (2) 20% food reduction (FR20, n = 30), and (3) 40% food reduction (FR40, n = 30). Non-invasive blood pressure was measured twice a week. Pulmonary arterial pressure (PAP) was measured using isolated/perfused lungs. The isolated vascular reactivity was assessed using double-wire myographs. FR rats exhibited a lower mean arterial pressure and heart rate; however, only the FR40 group exhibited statistically significant differences. We observed that FR enhanced sensitivity (EC 50 ) to vasoconstriction induced by the α1-adrenoreceptor phenylephrine (PhE) but not to serotonin, U46619, or high K + in the mesenteric arteries. PhE-mediated vasoconstriction in the mesenteric arteries was eliminated in the presence of the eNOS inhibitor (L-NAME). In addition, incubation with NOX2/4 inhibitors (apocynin, GKT137831, and VAS2870) and the reactive oxygen species (ROS) scavenger inhibitor (Tiron) eliminated the differences in PhE-mediated vasoconstriction, but the cyclooxygenase inhibitor (indomethacin) in the mesenteric arteries did not. Augmentation of α1-adrenergic-mediated contraction via the inhibition of the eNOS-NO pathway increased the activation of ROS through NOX2/4 in response to FR. Reduced eNOS-NO signaling may be a pathophysiological counterbalance to prevent hypovolemic shock in response to FR.

Pulmonary hypertension (PH) is a severe and progressive disease that causes elevated right ventricular systolic pressure, right ventricular hypertrophy and ultimately right heart failure. However, the underlying pathophysiologic mechanisms are poorly understood. We previously showed that 3,4-l-dihydroxylphenyalanine (DOPA) sensitizes vasomotor response to sympathetic tone via coupling between the adrenergic receptor alpha1 (ADRA1) and a G protein-coupled receptor 143 (GPR143), a DOPA receptor. We investigated whether DOPA similarly enhances ADRA1-mediated contraction in pulmonary arteries isolated from rats, and whether GPR143 is involved in the PH pathogenesis. Pretreating the isolated pulmonary arteries with DOPA 1 μM enhanced vasoconstriction in response to phenylephrine, an ADRA1 agonist, but not to U-46619, a thromboxane A2 agonist or endothelin-1. We generated Gpr143 gene-deficient (Gpr143 -/y ) rats, and confirmed that DOPA did not augment phenylephrine-induced contractile response in Gpr143 -/y rat pulmonary arteries. We utilized a rat model of monocrotaline (MCT)-induced PH. In the MCT model, the right ventricular systolic pressure was attenuated in the Gpr143 -/y rats than in WT rats. Phenylephrine-induced cell migration and proliferation were also suppressed in Gpr143 -/y pulmonary artery smooth muscle cells than in WT cells. Our result suggests that GPR143 is involved in the PH pathogenesis in the rat models of PH., Competing Interests: Declaration of competing interest The authors declare that there are no conflicts of interest., (Copyright © 2021 The Authors. Production and hosting by Elsevier B.V. All rights reserved.)

Our previous study showed the intrinsic ability of descending noradrenergic neurons projecting from the locus coeruleus to the spinal dorsal horn (SDH) to suppress itch-related behaviors. Noradrenaline and α 1A -adrenaline receptor (α 1A -AR) agonist increase inhibitory synaptic inputs onto SDH interneurons expressing gastrin-releasing peptide receptors, which are essential for itch transmission. However, the contribution of α 1A -ARs expressed in SDH inhibitory interneurons to itch-related behavior remains to be determined. In this study, RNAscope in situ hybridization revealed that Adra1a mRNA is expressed in SDH inhibitory interneurons that are positive for Slc32a1 mRNA (known as vesicular GABA transporter). Mice with conditional knock-out of α 1A -ARs in inhibitory interneurons (Vgat-Cre;Adra1a flox/flox mice) exhibited an increase in scratching behavior when induced by an intradermal injection of chloroquine, but not compound 48/80, which are known as models of histamine-independent and dependent itch, respectively. Furthermore, knockout of inhibitory neuronal α 1A -ARs in the SDH using the CRISPR-Cas9 system also increased the scratching behavior elicited by chloroquine but not compound 48/80. Our findings demonstrated for the first time that α 1A -ARs in SDH inhibitory interneurons contribute to the regulation of itch signaling with preference for histamine-independent itch.

Kidney is one of the important organs of the body.With both excretory and endocrine functions,it plays a vital role in regulating the normal physiological state.As a precursor of the nitric oxide(NO)synthesis in vivo ,L-arginine is involved in intracellular and intercellular signaling via NO,a vasoactive factor,thus plays a key role in maintaining the normal physiological functions of the kidney.Alpha1-adrenergic receptor(α 1 -AR)mediates sympathetic nerves to regulate the heart,blood vessels,and nervous system of the body.The α 1 -AR distributed in vascular smooth muscle mainly mediates vasoconstriction.The responsiveness of α 1 -AR to adrenergic agonists decreases in rat models of kidney failure,diabetes,hypertension,and left ventricular hypertrophy,which affects the hemodynamic state and vascular tone of the kidney.Here we analyze the ways via which L-arginine improves the responsiveness of α 1 -AR to its agonists by ellucidating the action mode of NO/α 1 -AR and their effects on renal functions.

Astrocytes are critical regulators of CNS function and are proposed to be heterogeneous in the developing brain and spinal cord. Here we identify a population of astrocytes located in the superficial laminae of the spinal dorsal horn (SDH) in adults that is genetically defined by Hes5. In vivo imaging revealed that noxious stimulation by intraplantar capsaicin injection activated Hes5 + SDH astrocytes via α 1A -adrenoceptors (α 1A -ARs) through descending noradrenergic signaling from the locus coeruleus. Intrathecal norepinephrine induced mechanical pain hypersensitivity via α 1A -ARs in Hes5 + astrocytes, and chemogenetic stimulation of Hes5 + SDH astrocytes was sufficient to produce the hypersensitivity. Furthermore, capsaicin-induced mechanical hypersensitivity was prevented by the inhibition of descending locus coeruleus-noradrenergic signaling onto Hes5 + astrocytes. Moreover, in a model of chronic pain, α 1A -ARs in Hes5 + astrocytes were critical regulators for determining an analgesic effect of duloxetine. Our findings identify a superficial SDH-selective astrocyte population that gates descending noradrenergic control of mechanosensory behavior.

Background/aims: Trace amines (TA) are small organic compounds that have neuromodulator activity due to their interaction with some neuron-related receptors, such as trace amine associated receptors (TAARs), α2-adrenergic receptor (α2-AR) and ß-adrenergic receptor (ß-AR). However, there is little information on whether TA and dopamine (DOP) can interact with other adrenergic receptors (ARs) such as the mammalian α1-AR and the bacterial counterpart QseC, which is involved in quorum sensing of some Gram-negative pathogens. The aim of this study was to investigate the interaction of TA and DOP with α1-AR and QseC., Methods: We performed an in silico study using 3D structure from SWISS MODEL and analyzed the protein interaction via molecular docking using PyMol, PoseView and PyRX 8.0. For the in vitro study, we investigated the QseC kinase activity by measuring the remaining ATP in a reaction containing QseC-enriched membrane incubated together with purified QseB and EPI, TA, DOP, or PTL respectively. We also measured the intracellular Ca++ levels, which represents the α1-AR activation, in LNCAP (pancreatic cell line) cells treated with EPI, TA, DOP and PTL respectively using a fluorescence-based assay. The LNCAP cell proliferation was measured using an MTT-based assay., Results: Our in silico analysis revealed that TAs and DOP have high binding affinity to the human α1-AR and the bacterial adrenergic receptor (QseC), comparable to epinephrine (EPI). Both are membrane-bound kinases. Experimental studies with pancreatic cell line (LNCAP) showed that the TAs and DOP act as α1-AR antagonist by counteracting the effect of EPI. In the presence of EPI, TA and DOP trigger an increase of the intracellular Ca++ levels in the LNCAP cells leading to an inhibition of cell proliferation. Although in silico data suggest an interaction of TA and DOP with QseC, they do not inhibit the kinase activity of QseC, a histidine kinase receptor involved in quorum sensing which is also sensitive to EPI., Conclusion: Our study showed that the TAs and DOP act as α1-AR antagonist but no effect was observed for QseC., Competing Interests: The authors have no conflicts of interest to declare., (© Copyright by the Author(s). Published by Cell Physiol Biochem Press.)

Temporomandibular Disorder (TMD) patients report amplification of pain in the masticatory muscles after psychological trauma or stressful conditions. The mechanisms underlying this phenomenon are yet to be elucidated. This study combined immunohistochemistry with single cell in vivo electrophysiology recordings of masticatory muscle afferent fibers to investigate the role of α 1 -adrenergic receptors in muscle nociception. It was found that a subset of trigeminal afferent fibers which innervate the masseter and temporal muscles expressed α 1a , α 1b and α 1d receptors, including a smaller number of putative nociceptors which co-expressed TrpV 1 receptors. Local injection of the selective α 1 adrenergic receptor agonist phenylephrine into masticatory muscle decreased and increased the mechanical activation threshold of slow and fast conducting afferent fibers, respectively. This effect was reversed by co-administration of the α 1 selective antagonist terazosin. To rule out the possibility that local ischemia was responsible for the observed effect of phenylephrine on masticatory muscle afferent fibers, additional experiments were conducted where blood flow to the masticatory muscle was reduced by common carotid artery occlusion. This investigation found that muscle blood flow occlusion increased the mechanical activation threshold of the majority of masticatory muscle afferent fibers unrelated to conduction velocity. These findings suggest that under conditions of increased sympathetic tone, such as those related to stress, noradrenaline may sensitize masticatory muscle nociceptors to increase pain and desensitize muscle proprioceptors to alter muscle tone, through activation of α 1 receptors., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Somatosensory afferent transmission strength is controlled by several presynaptic mechanisms that reduce transmitter release at the spinal cord level. We focused this investigation on the role of α-adrenoceptors in modulating sensory transmission in low-threshold myelinated afferents and in pathways mediating primary afferent depolarization (PAD) of neonatal mouse spinal cord. We hypothesized that the activation of α-adrenoceptors depresses low threshold-evoked synaptic transmission and inhibits pathways mediating PAD. Extracellular field potentials (EFPs) recorded in the deep dorsal horn assessed adrenergic modulation of population monosynaptic transmission, while dorsal root potentials (DRPs) recorded at root entry zone assessed adrenergic modulation of PAD. We found that noradrenaline (NA) and the α 1 -adrenoceptor agonists phenylephrine and cirazoline depressed synaptic transmission (by 15, 14 and 22%, respectively). DRPs were also depressed by NA, phenylephrine and cirazoline (by 62, 30, and 64%, respectively), and by the α 2 -adrenoceptor agonist clonidine, although to a lower extent (20%). We conclude that NA depresses monosynaptic transmission of myelinated afferents onto deep dorsal horn neurons via α 1 -adrenoceptors and inhibits interneuronal pathways mediating PAD through the activation of α 1 - and α 2 -adrenoceptors. The functional significance of these modulatory actions in shaping cutaneous and muscle sensory information during motor behaviors requires further study.

Pulmonary veins (PV) are involved in the pathophysiology of paroxysmal atrial fibrillation. In the rat, left atrium (LA) and PV cardiomyocytes have different reactions to α1-adrenergic receptor activation. In freely beating atria-PV preparations, we found that electrical field potential (EFP) originated from the sino-atrial node propagated through the LA and the PV. The α1-adrenergic receptor agonist cirazoline induced a progressive loss of EFP conduction in the PV whereas it was maintained in the LA. This could be reproduced in preparations electrically paced at 5 Hz in LA. During pacing at 10 Hz in the PV where high firing rate ectopic foci can occur, cirazoline stopped EFP conduction from the PV to the LA, which allowed the sino-atrial node to resume its pace-making function. Loss of conduction in the PV was associated with depolarization of the diastolic membrane potential of PV cardiomyocytes. Adenosine, which reversed the cirazoline-induced depolarization of the diastolic membrane potential of PV cardiomyocytes, restored full over-shooting action potentials and EFP conduction in the PV. In conclusion, selective activation of α1-adrenergic receptors results in the abolition of electrical conduction within the PV. These results highlight a potentially novel pharmacological approach to treat paroxysmal atrial fibrillation by targeting directly the PV myocardium.

Sphingosine-1-phosphate (S1P) has been implicated recently in the physiology and pathology of the cardiovascular system including regulation of vascular tone. Pilot experiments showed that the vasoconstrictor effect of S1P was enhanced markedly in the presence of phenylephrine (PE). Based on this observation, we hypothesized that S1P might modulate α 1 -adrenergic vasoactivity. In murine aortas, a 20-minute exposure to S1P but not to its vehicle increased the E max and decreased the EC 50 of PE-induced contractions indicating a hyperreactivity to α 1 -adrenergic stimulation. The potentiating effect of S1P disappeared in S1P2 but not in S1P3 receptor-deficient vessels. In addition, smooth muscle specific conditional deletion of G 12/13 proteins or pharmacological inhibition of the Rho-associated protein kinase (ROCK) by Y-27632 or fasudil abolished the effect of S1P on α 1 -adrenergic vasoconstriction. Unexpectedly, PE-induced contractions remained enhanced markedly as late as three hours after S1P-exposure in wild-type (WT) and S1P3 KO but not in S1P2 KO vessels. In conclusion, the S1P-S1P2-G 12/13 -ROCK signaling pathway appears to have a major influence on α 1 -adrenergic vasoactivity. This cooperativity might lead to sustained vasoconstriction when increased sympathetic tone is accompanied by increased S1P production as it occurs during acute coronary syndrome and stroke.

Benign prostatic hyperplasia (BPH) is an aging-related and progressive disease linked to an up-regulation of α 1 -adrenoceptors. The participation of EGF receptors (EGFR) in the GPCRs' signalosome has been described but so far data about the contribution of these receptors to prostatic stromal hyperplasia are scanty. We isolated and cultured vimentin-positive prostate stromal cells obtained from BPH patients. According to intracellular Ca 2+ measurements, cell proliferation and Western blotting assays, these cultured hyperplastic stromal cells express functional α 1- adrenoceptors and EGFR, and proliferate in response to the α 1- adrenoceptor agonist phenylephrine. Interestingly, in these cells the inhibition of EGFR signaling with GM6001, CRM197, AG1478 or PD98059 was associated with full blockage of α 1 -adrenoceptor-mediated cell proliferation, while cell treatment with each inhibitor alone did not alter basal cell growth. Moreover, the co-incubation of AG1478 (EGFR inhibitor) with α 1A/ α 1D -adrenoceptor antagonists showed no additive inhibitory effect. These findings highlight a putative role of EGFR signaling to α 1 -adrenoceptor-mediated human prostate hyperplasia, suggesting that the inhibition of this transactivation cascade could be useful to reduce BPH progression., (Copyright © 2019 Elsevier Inc. All rights reserved.)

It is recognized that stress can induce cardiac dysfunction, but the underlying mechanisms are not well understood. The present study aimed to test the hypothesis that chronic negative stress leads to alterations in DNA methylation of certain cardiac genes, which in turn contribute to pathologic remodeling of the heart. We found that mice that were exposed to chronic restraint stress (CRS) for 4 wk exhibited cardiac remodeling toward heart failure, as characterized by ventricular chamber dilatation, wall thinning, and decreased contractility. CRS also induced cardiac arrhythmias, including intermittent sinus tachycardia and bradycardia, frequent premature ventricular contraction, and sporadic atrioventricular conduction block. Circulating levels of stress hormones were elevated, and the cardiac expression of tyrosine hydroxylase, a marker of sympathetic innervation, was increased in CRS mice. Using reduced representation bisulfite sequencing, we found that although CRS did not lead to global changes in DNA methylation in the murine heart, it nevertheless altered methylation at specific genes that are associated with the dilated cardiomyopathy (DCM) ( e.g. , desmin) and adrenergic signaling of cardiomyocytes (ASPC) ( e.g. , adrenergic receptor-α1) pathways. We conclude that CRS induces cardiac remodeling and arrhythmias, potentially through altered methylation of myocardial genes associated with the DCM and ASPC pathways.-Zhang, P., Li, T., Liu, Y.-Q., Zhang, H., Xue, S.-M., Li, G., Cheng, H.-Y.M., Cao, J.-M. Contribution of DNA methylation in chronic stress-induced cardiac remodeling and arrhythmias in mice.

KCNQ1 (Kv7.1 or KvLQT1) plays important physiological roles in various tissues forming potassium channels with KCNE subunits. Among the channels formed by KCNQ1 and KCNE subunits, the best studied is the slow delayed rectifier potassium channel in the heart, the I Ks (KCNQ1/KCNE1) channel, which is critical for repolarization of cardiac action potential. The KCNQ1 channel is internalized by Nedd4/Nedd4-like ligase-dependent ubiquitination. It is also reported that phosphorylation of KCNE1 by PKC results in internalization of the KCNQ1/KCNE1 channel. Because we have observed down-regulation of KCNQ1/KCNE1 currents by activation of the α 1 -adrenergic receptor (α 1 AR) that activates PKC, this study investigated whether α 1 AR causes internalization of the KCNQ1 protein. We fused HaloTag to the extracellular region of KCNQ1 (Halo-KCNQ1) and co-expressed it with α 1 ARs in HEK293 cells. The KCNQ1 protein on the cell surface was selectively labeled with membrane-impermeable HaloTag ligands, and changes in its localization were monitored by confocal fluorescence microscopy. Activation of α 1A AR and α 1B AR caused marked internalization of KCNQ1, which was not KCNE1-dependent. Internalization of KCNQ1 by α 1 AR activation was inhibited by disruption of the PY motif or the YXXΦ motif in the C-terminus. Double staining for the receptor and the channel revealed that KCNQ1 internalization was independent of α 1 AR internalization. Our results suggest that α 1 AR-mediated direct internalization of KCNQ1 is AP2/clathrin-dependent and may be triggered by ubiquitination of KCNQ1 via the AMP dependent kinase (AMPK)/Nedd4-2 pathway. When phenylephrine was applied to rat neonatal cardiomyocytes transfected with KCNQ1 and α 1 AR, the KCNQ1 protein was internalized. The internalization of KCNQ1 by α 1 AR would affect pathophysiology in a variety of tissues expressing KCNQ1, which merits further in vivo study., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The locus coeruleus (LC) supplies norepinephrine (NE) to the entire forebrain and regulates many fundamental brain functions. Studies in humans have suggested that strong LC activation might shift network connectivity to favor salience processing. To causally test this hypothesis, we use a mouse model to study the effect of LC stimulation on large-scale functional connectivity by combining chemogenetic activation of the LC with resting-state fMRI, an approach we term "chemo-connectomics." We show that LC activation rapidly interrupts ongoing behavior and strongly increases brain-wide connectivity, with the most profound effects in the salience and amygdala networks. Functional connectivity changes strongly correlate with transcript levels of alpha-1 and beta-1 adrenergic receptors across the brain, and functional network connectivity correlates with NE turnover within select brain regions. We propose that these changes in large-scale network connectivity are critical for optimizing neural processing in the context of increased vigilance and threat detection., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Medical therapy of lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH) targets smooth muscle contraction in the prostate, for which α 1A -adrenoceptor (α 1A -AR) antagonists have been considered to be the primary therapeutic method. We investigated the effects and underlying mechanisms of isocorynoxeine (ICN), one of indole alkaloids from Uncaria, on the treatment of LUTS secondary to BPH via α 1A -ARs in mice. The effect of ICN on prostatic contractility was studied via myographic measurements in the prostates of rabbits. The effects of ICN on bladder function, serum-hormone levels, bladder histology, and prostate histology were determined in testosterone propionate-induced prostatic hyperplasic wild-type (WT) and α 1A -AR knockout (α 1A -KO) mice. The cytotoxicity of ICN in cultured human prostatic stromal cells (WPMY-1) was assessed by the following: a cell-counting kit, measuring the relaxant effect on WPMY-1 by a collagen gel contraction assay, intracellular Ca 2+ mobilization indicated by Fluo-4, cytoskeletal organization by phalloidin staining, and expressions of α 1A -AR-mediated key messengers by western blot analyses. ICN non-competitively antagonized the contractions of prostates induced by α 1A -AR agonists. ICN treatment improved bladder functions in prostatic hyperplasic WT mice, whereas it failed to ameliorate bladder functions in prostatic hyperplasic α 1A -KO mice. In WPMY-1, ICN relaxed cell contractions on collagen gels, disrupted F-actin organization, inhibited α 1A -AR agonist-stimulated Ca 2+ mobilization, and antagonized α 1A -ARs via the RhoA/ROCK2/MLC signaling pathway. Our results suggest that ICN may be a promising therapeutic drug for targeting α 1A -ARs in the treatment of BPH/LUTS., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Oxaliplatin is a chemotherapeutic agent used for metastatic colon and other advanced cancers. Most common side effect of oxaliplatin is peripheral neuropathy, manifested in mechanical and cold allodynia. Although the analgesic effect of bee venom has been proven to be effective against oxaliplatin-induced peripheral neuropathy, the effect of its major component; melittin has not been studied yet. Thus, in this study, we investigated whether melittin has an analgesic effect on oxaliplatin-induced allodynia. Intraperitoneal single injection of oxaliplatin (6 mg/kg) induced mechanical and cold allodynia, resulting in increased withdrawal behavior in response to von Frey filaments and acetone drop on hind paw. Subcutaneous melittin injection on acupoint ST36 (0.5 mg/kg) alleviated oxaliplatin-induced mechanical and cold allodynia. In electrophysiological study, using spinal in vivo extracellular recording, it was shown that oxaliplatin-induced hyperexcitation of spinal wide dynamic range neurons in response to peripheral stimuli, and melittin administration inhibited this neuronal activity. In behavioral assessment, analgesic effect of melittin was blocked by intrathecal α1- and α2- adrenergic receptor antagonists administration. Based on these results, we suggest that melittin could be used as an analgesic on oxaliplatin-induced peripheral neuropathy, and that its effect is mediated by activating the spinal α1- and α2-adrenergic receptors.

Electroencephalogram monitoring during propofol (PRO) anesthesia typically features low-frequency oscillations, which may be involved with thalamic reticular nucleus (TRN) modulation. TRN receives noradrenergic inputs from the locus coeruleus (LC). We hypothesized that specific noradrenergic connections in the TRN may contribute to the emergence from PRO anesthesia. Intranuclei norepinephrine (NE) injections ( n = 10) and designer receptors exclusively activated by designer drugs (DREADDs) ( n = 10) were used to investigate the role of noradrenergic inputs from the LC to the TRN during PRO anesthesia. Whole-cell recording in acute brain slice preparations was used to identify the type of adrenoceptor that regulates noradrenergic innervation in the TRN. An intracerebral injection of NE into the TRN delays arousal in mice recovering from PRO anesthesia (means ± sd; 486.6 ± 57.32 s for the NE injection group vs. 422.4 ± 48.19 s for the control group; P = 0.0143) and increases the cortical-δ (0.1-4 Hz, 25.4 ± 2.9 for the NE injection group vs. 21.0 ± 1.7 for the control group; P = 0.0094) oscillation. An intra-TRN injection of NE also decreased the EC 50 of PRO-induced unconsciousness (57.05 ± 1.78 mg/kg for the NE injection group vs. 72.44 ± 3.23 mg/kg for the control group; P = 0.0096). Moreover, the activation of LC-noradrenergic nerve terminals in the TRN using DREADDs increased the recovery time [466.1 ± 44.57 s for the clozapine N-oxide (CNO) injection group vs. 426.1 ± 38.75 s for the control group; P = 0.0033], decreased the EC 50 of PRO-induced unconsciousness (64.77 ± 3.40 mg/kg for the CNO injection group vs. 74.00 ± 2.08 mg/kg for the control group; P = 0.0081), and increased the cortical-δ oscillation during PRO anesthesia (23.29 ± 2.58 for the CNO injection group vs. 19.56 ± 1.9 for the control group; P = 0.0213). In addition, whole-cell recording revealed that NE augmented the inhibitory postsynaptic currents in the TRN neurons via the α1-adrenoceptor. Our data indicated that enhanced NE signaling at the noradrenergic terminals of the LC-TRN projection delays arousal from general anesthesia, which is likely mediated by the α1-adrenoceptor activation. Our findings open a door for further understanding of the functions of various LC targets in both anesthesia and arousal.-Zhang, Y., Fu, B., Liu, C., Yu, S., Luo, T., Zhang, L., Zhou, W., Yu, T. Activation of noradrenergic terminals in the reticular thalamus delays arousal from propofol anesthesia in mice.

Low frequency stimulation (LFS) has anticonvulsant effect and may restore the ability of long-term potentiation (LTP) to the epileptic brain. The mechanisms of LFS have not been completely determined. Here, we showed that LTP induction was impaired following in vitro epileptiform activity (EA) in hippocampal slices, but application of LFS prevented this impairment. Then, we investigated the involvement of α-adrenergic receptors in this effect of LFS. EA was induced by increasing the extracellular K + concentration to 12 mM and EPSPs were recorded from CA1 neurons in whole cell configuration. EA increased EPSP amplitude from 6.9 ± 0.7 mV to 9.6 ± 0.6 mV. For LTP induction, the Schaffer collaterals were stimulated by high frequency stimulation (HFS; two trains of 100 pulses, 100 Hz at the interval of 20 s). The application of HFS resulted in 40.9 ± 2.3% increase in the amplitude of EPSPs. However, following EA, HFS could not produce any significant changes in EPSP amplitude. Administration of LFS (1 Hz, 900 pulses) to Schaffer collaterals at the beginning of EA restored LTP induction to the hippocampal slices and HFS increased the EPSPs amplitude up to 41.7 ± 3.1% of baseline. When slices were perfused by prazosin (α 1 -adrenergic receptor antagonist; 10 μM) before and during LFS application, LFS improvement on LTP induction was reduced significantly. Perfusion of slices by yohimbine (α 2 -adrenergic receptor antagonist; 5 μM) had no effect on LFS action. Therefore, it may be concluded that following epileptiform activity, LFS can improve the impairment of LTP generation through α 1 , but not α 2 , adrenergic receptor activity., (Copyright © 2019 IBRO. Published by Elsevier Ltd. All rights reserved.)

Background: Homeostatic plasticity in mesolimbic dopamine (DA) neurons plays an essential role in mediating resilience to social stress. Recent evidence implicates an association between stress resilience and projections from the locus coeruleus (LC) to the ventral tegmental area (VTA) (LC→VTA) DA system. However, the precise circuitry and molecular mechanisms of the homeostatic plasticity in mesolimbic DA neurons mediated by the LC→VTA circuitry, and its role in conferring resilience to social defeat stress, have not been described., Methods: In a well-established chronic social defeat stress model of depression, using projection-specific electrophysiological recordings and optogenetic, pharmacological, and molecular profiling techniques, we investigated the functional role and molecular basis of an LC→VTA circuit in conferring resilience to social defeat stress., Results: We found that LC neurons projecting to the VTA exhibit enhanced firing activity in resilient, but not susceptible, mice. Optogenetically mimicking this firing adaptation in susceptible mice reverses their depression-related behaviors, and induces reversal of cellular hyperactivity and homeostatic plasticity in VTA DA neurons projecting to the nucleus accumbens. Circuit-specific molecular profiling studies reveal that α 1 - and β 3 -adrenergic receptors are highly expressed in VTA→nucleus accumbens DA neurons. Pharmacologically activating these receptors induces similar proresilient effects at the ion channel and cellular and behavioral levels, whereas antagonizing these receptors blocks the proresilient effect of optogenetic activation of LC→VTA circuit neurons in susceptible mice., Conclusions: These findings reveal a key role of the LC→VTA circuit in mediating homeostatic plasticity in stress resilience and reveal α 1 - and β 3 -adrenergic receptors as new molecular targets for therapeutically promoting resilience., (Copyright © 2018 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Background: Dysregulation of arousal is symptomatic of numerous psychiatric disorders. Previous research has shown that the activity of dopamine (DA) neurons in the ventral periaqueductal gray (vPAG) tracks with arousal state, and lesions of vPAG DA cells increase sleep. However, the circuitry controlling these wake-promoting DA neurons is unknown., Methods: This study combined designer receptors exclusively activated by designer drugs (DREADDs), behavioral pharmacology, electrophysiology, and immunoelectron microscopy in male and female mice to elucidate mechanisms in the vPAG that promote arousal., Results: Activation of locus coeruleus projections to the vPAG or vPAG DA neurons induced by DREADDs promoted arousal. Similarly, agonist stimulation of vPAG alpha1-adrenergic receptors (α1ARs) increased latency to fall asleep, whereas α1AR blockade had the opposite effect. α1AR stimulation drove vPAG DA activity in a glutamate-dependent, action potential-independent manner. Compared with other dopaminergic brain regions, α1ARs were enriched on astrocytes in the vPAG, and mimicking α1AR transmission specifically in vPAG astrocytes via Gq-DREADDS was sufficient to increase arousal. In general, the wake-promoting effects observed were not accompanied by hyperactivity., Conclusions: These experiments revealed that vPAG α1ARs increase arousal, promote glutamatergic input onto vPAG DA neurons, and are abundantly expressed on astrocytes. Activation of locus coeruleus inputs, vPAG astrocytes, or vPAG DA neurons increase sleep latency but do not produce hyperactivity. Together, these results support an arousal circuit whereby noradrenergic transmission at astrocytic α1ARs activates wake-promoting vPAG DA neurons via glutamate transmission., (Copyright © 2018 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.)

Our previous studies have shown that phenylephrine-induced contraction of cutaneous arteries is primarily mediated via α 1A -adrenoceptors, but not α 1D -adrenoceptors that generally mediate vascular contraction, and that the larger part of the contraction is induced in a voltage-dependent Ca 2+ channel (VDCC)-independent manner. Here, we investigated the mechanism underlying the smaller part of the α 1A -adrenoceptor-mediated contraction, i.e., VDCC-dependent one, in cutaneous arteries. Isometric contraction was measured with wire myograph in endothelium-denuded tail and iliac arterial rings isolated from male Wistar rats. LOE908 (10 µM), a cation channel blocker, partially inhibited the contraction induced by phenylephrine in tail and iliac arteries. Nifedipine (10 µM) further suppressed the phenylephrine-induced contraction that remained in the presence of LOE908 (10 µM) in iliac arteries but barely in tail arteries, suggesting that phenylephrine-induced depolarization in tail arteries is due to the activation of LOE908-sensitive cation channels. In iliac arteries, the contraction induced by A-61603, a specific α 1A -adrenoceptor agonist, was also partially inhibited by LOE908 (10 µM); however, nifedipine had little effect on the A-61603-induced contraction that remained in the presence of LOE908 (10 µM), suggesting that depolarization mediated via α 1A -adrenoceptors is due to the activation of LOE908-sensitive cation channels even in iliac arteries. These results suggest that membrane depolarization mediated via α 1Α -adrenoceptors is caused by cation influx through LOE908-sensitive cation channels. Less contribution of VDCC to phenylephrine-induced contraction in tail arteries compared to in iliac arteries is likely due to that α 1Α -adrenoceptor-mediated activation of VDCC is caused only by depolarization via cation influx through LOE908-sensitive cation channels.

Aim: To examine putative interaction between adrenergic and muscarinic contractile activation in the human urinary outflow tract., Methods: Tissue from the trigone and prostatic urethra was obtained from 12 cystectomy and 16 prostatectomy specimen. Contractions were elicited by exposure to exogenous agonists before and after inhibition of Rho kinase and protein kinase c (PKC). Immunofluorescence and Western-blot studies were performed using antibodies to muscarinic M3-receptors (M3-R) and alpha1A-adrenoreceptors (alpha1A-AR). The study is registered with ClinicalTrials.gov, number NCT01227447., Results: There was strong co-localization of M3-R and alpha1A-AR on trigonal and urethral myocytes. Western blot analysis revealed a significantly higher expression of alpha1A-AR in the superficial than in the deep trigone. Phenylephrine (PE, 1 μm) augmented contractions induced by carbachol (CA, 3 μm) to more than threefold control in the male superficial trigone, and to about sevenfold control in the proximal urethra. No such potentiation could be detected in female bladder outlet. Both PKC inhibitor GF 109203X and Rho kinase inhibitor Y-27632 reduced responses to 1 μM PE as well as to 3 μM CA significantly. However, the synergistic effect of the combined intervention remained proportionally unaffected., Conclusions: Muscarinic and adrenergic receptor activation exerts a strong synergistic effect in the male human bladder trigone and proximal urethra., (© 2018 Wiley Periodicals, Inc.)

α 1 -adrenoceptor antagonists can impact upon sexual function and have potential in the treatment of erectile dysfunction. Human erectile tissue contains predominantly α 1A -adrenoceptors, and here we examined whether contractions of this tissue are mediated by the functional phenotype, the α 1L -adrenoceptor. Functional experiments using subtype selective agonists and antagonists, along with radioligand ([ 3 H]tamsulosin) binding assays, were used to determine the α 1 -adrenoceptor population. A61603, a α 1A -adrenoceptor agonist, was a full agonist with a potency 21-fold greater than that of noradrenaline. The α 1A - and α 1D -adrenoceptor antagonist tamsulosin antagonized noradrenaline responses with high affinity (pK D  = 9.7 ± 0.3), whilst BMY7378 (100 nM) (α 1D -adrenoceptor antagonist) failed to antagonize responses. In contrast, relatively low affinity estimates were obtained for both prazosin (pK D  = 8.2 ± 0.1) and RS17053 (pK D  = 6.9 ± 0.2), antagonists which discriminate between the α 1A - and α 1L -adrenoceptors. [ 3 H]Tamsulosin bound with high affinity to the receptors of human erectile tissue (pK D  = 10.3 ± 0.1) with a receptor density of 28.1 ± 1.4 fmol mg -1 protein. Prazosin displacement of [ 3 H]tamsulosin binding revealed a single homogenous population of binding sites with a relatively low affinity for prazosin (pK i  = 8.9). Taken together these data confirm that the receptor mediating contraction in human erectile tissue has the pharmacological properties of the α 1L -adrenoceptor., (Copyright © 2018 The Authors. Production and hosting by Elsevier B.V. All rights reserved.)

While the cerebral autoregulation sufficiently protects subcortical brain regions during hypoxia or asphyxia, the cerebral cortex is not as adequately protected, which suggests that regulation of the cerebral blood flow (CBF) is area-specific. Hypoxia was induced by inhalation of 5% oxygen, for reoxygenation 100% oxygen was used. Cortical and subcortical CBF (by laser Doppler flowmetry), blood gases, mean arterial blood pressure (MABP), heart rate and renal blood flow were constantly monitored. Low dosed urapidil was used for α1A-adrenergic receptor blockade. Western blotting was used to determine adrenergic receptor signalling mediators in brain arterioles. During hypoxia cortical CBF decreased to 72 ± 11% (mean reduction 11 ± 3%, p < 0.001) of baseline, whereas subcortical CBF increased to 168±18% (mean increase 43 ± 5%, p < 0.001). Reoxygenation led to peak CBF of 194 ± 27% in the subcortex, and restored cortical CBF. α1A-Adrenergic blockade led to minor changes in cortical CBF, but massively reduced subcortical CBF during hypoxia and reoxygenation-almost aligning CBF in both brain regions. Correlation analyses revealed that α1A-adrenergic blockade renders all CBF-responses pressure-passive during hypoxia and reoxygenation, and confirmed the necessity of α1A-adrenergic signalling for coupling of CBF-responses to oxygen saturation. Expression levels and activation state of key signalling-mediators of α1-receptors (NOSs, CREB, ERK1/2) did not differ between cortex and subcortex. The dichotomy between subcortical and cortical CBF during hypoxia and reoxygenation critically depends on α1A-adrenergic receptors, but not on differential expression of signalling-mediators: signalling through the α1A-subtype is a prerequisite for cortical/subcortical redistribution of CBF., Competing Interests: The authors have declared that no competing interests exist.

Our previous studies have shown that α 1 -adrenoceptors, in addition to α 2 -adrenoceptors, are involved in enhanced contraction of cutaneous blood vessels during cooling. The present study aimed to elucidate the mechanism underlying it. In tail and iliac arteries isolated from rats, isometric contraction was measured using a myograph and the phosphorylation level of myosin phosphatase target subunit 1 (MYPT1) was quantified by western blotting. The phenylephrine-induced contraction was enhanced by cooling to 24 °C in tail arteries, but was suppressed in iliac arteries. Endothelium denudation or treatment with iberiotoxin enhanced the phenylephrine-induced contraction in tail arteries at 37 °C; however, neither affected the contraction at 24 °C. The phenylephrine-induced contraction at 37 °C was largely suppressed by nifedipine in iliac arteries, but only slightly in tail arteries. The Rho kinase inhibitor H-1152 largely suppressed the phenylephrine-induced contraction at 24 °C, but only slightly at 37 °C, in both arteries. The phosphorylation level of MYPT1 at Thr855 in tail arteries was increased by the cooling. Taken together, these results suggest the following mechanism in regard to cooling-induced enhancement of α 1 -adrenoceptor-mediated contraction in tail arteries: Cooling enhances the contraction of tail arteries via α 1 -adrenoceptor stimulation by reducing endothelium-dependent, large-conductance Ca 2+ -activated K + channel-mediated relaxation and by inducing Rho kinase-mediated Ca 2+ sensitization, although the latter occurs even in iliac arteries. A smaller contribution of voltage-dependent Ca 2+ channels, which are largely suppressed by cooling, to α 1 -adrenoceptor-mediated contraction in tail arteries seems to be more crucially involved in the appearance of the enhanced contractile response to cooling., (Copyright © 2018. Published by Elsevier B.V.)

We have systematically investigated how vascular smooth muscle α 1 -adrenoceptor activation impacts endothelium-mediated vasodilation in isolated, myogenically active, rat cremaster muscle 1A arteries. Cannulated cremaster arteries were pressurized intraluminally to 70 mmHg to induce myogenic tone, and exposed to vasoactive agents via bath superfusion at 34°C. Smooth muscle membrane potential was measured via sharp microelectrode recordings in pressurized, myogenic arteries. The α 1 -adrenergic agonist phenylephrine (25-100 nmol/L) produced further constriction of myogenic arteries, but did not alter the vasorelaxant responses to acetylcholine (0.3 μmol/L), SKA-31 (an activator of endothelial Ca 2+ -dependent K + channels) (3 μmol/L) or sodium nitroprusside (10 μmol/L). Exposure to 0.25-1 μmol/L phenylephrine or 1 μmol/L norepinephrine generated more robust constrictions, and also enhanced the vasodilations evoked by acetylcholine and SKA-31, but not by sodium nitroprusside. In contrast, the thromboxane receptor agonist U46619 (250 nmol/L) dampened responses to all three vasodilators. Phenylephrine exposure depolarized myogenic arteries, and mimicking this effect with 4-aminopyridine (1 mmol/L) was sufficient to augment the SKA-31-evoked vasodilation. Inhibition of L-type Ca 2+ channels by 1 μmol/L nifedipine decreased myogenic tone, phenylephrine-induced constriction and prevented α 1 -adrenergic enhancement of endothelium-evoked vasodilation; these latter deficits were overcome by exposure to 3 and 10 μmol/L phenylephrine. Mechanistically, augmentation of ACh-evoked dilation by phenylephrine was dampened by eNOS inhibition and abolished by blockade of endothelial KCa channels. Collectively, these data suggest that increasing α 1 -adrenoceptor activation beyond a threshold level augments endothelium-evoked vasodilation, likely by triggering transcellular signaling between smooth muscle and the endothelium. Physiologically, this negative feedback process may serve as a "brake" to limit the extent of vasoconstriction in the skeletal microcirculation evoked by the elevated sympathetic tone., (© 2018 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.)

The signalling functions of many G protein-coupled receptors (GPCRs) expressed in the myocardium are incompletely understood. Among these are the endothelin receptor (ETR) family and α 1 -adrenergic receptor (α 1 -AR), which are thought to couple to the G protein Gαq. In this study, we used transcriptome analysis to compare the signalling networks downstream of these receptors in primary neonatal rat cardiomyocytes. This analysis indicated increased expression of target genes of cAMP responsive element modulator (CREM) after 24 h treatment with the α 1 -AR agonist phenylephrine, but not the ETR agonist endothelin-1, suggesting a specific role for the α 1 -AR in promoting cAMP production in cardiomyocytes. To validate the difference observed between these two GPCRs, we used heterologous expression of the receptors and genetically encoded biosensors in HEK 293 cell lines. We validated that both α 1A - and α 1B -AR subtypes were able to lead to the accumulation of cAMP in response to phenylephrine in both the nucleus and cytoplasm in a Gαs-dependent manner. However, the ETR subtype ETA did not affect cAMP levels in either compartment. All three receptors were coupled to Gαq signalling as expected. Further, we showed that activation of PKA in different compartments was α 1 -AR subtype specific, with α 1B -AR able to activate PKA in the cytoplasm and nucleus and α 1A -AR only able to in the nucleus. We provide evidence for a pathway downstream of the α 1 -AR, and show that distinct pools of a receptor lead to differential activation of downstream effector proteins dependent on their cellular compartment., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Left ventricular hypertrophy (LVH) is associated with decreased responsiveness of renal α1-adrenoreceptors subtypes to adrenergic agonists. Nitric oxide donors are known to have antihypertrophic effects however their impact on responsiveness of renal α1-adrenoreceptors subtypes is unknown. This study investigated the impact of nitric oxide (NO) and its potential interaction with the responsiveness of renal α1-adrenoreceptors subtypes to adrenergic stimulation in rats with left ventricular hypertrophy (LVH). This study also explored the impact of NO donor on CSE expression in normal and LVH kidney. LVH was induced using isoprenaline and caffeine in drinking water for 2 weeks while NO donor (L-arginine, 1.25g/Lin drinking water) was given for 5 weeks. Intrarenal noradrenaline, phenylephrine and methoxamine responses were determined in the absence and presence of selective α1-adrenoceptor antagonists, 5- methylurapidil (5-MeU), chloroethylclonidine (CeC) and BMY 7378. Renal cortical endothelial nitric oxide synthase mRNA was upregulated 7 fold while that of cystathione γ lyase was unaltered in the NO treated LVH rats (LVH-NO) group compared to LVH group. The responsiveness of renal α1A, α1B and α1D-adrenoceptors in the low dose and high dose phases of 5-MeU, CEC and BMY7378 to adrenergic agonists was increased along with cGMP in the kidney of LVH-NO group. These findings suggest that exogenous NO precursor up-regulated the renal eNOS/NO/cGMP pathway in LVH rats and resulted in augmented α1A, α1B and α1D adrenoreceptors responsiveness to the adrenergic agonists. There is a positive interaction between H2S and NO production in normal animals but this interaction appears absent in LVH animals.

Rationale: We have hypothesized that post-infarction cardiac remodeling can be influenced by shifts in the balance between intracellular mediators of "pathologic" and "physiologic" hypertrophy. Although alpha1 adrenergic receptors (alpha1-ARs) mediate pro-adaptive hypertrophy during pressure overload, little is known about their role or downstream mediators after myocardial infarction., Methods: We performed loss-of-function experiments via coronary ligation in alpha1A-AR knockout (AKO) mice. Post-myocardial infarction (MI) remodeling was evaluated via echocardiography, quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis of cardiac fetal gene expression, histologic analysis of myocyte size, post-MI fibrosis and apoptosis, and Western blot analysis of apoptotic regulators., Results: Alpha1A-AR knockout paradoxically increased post-MI hypertrophy compared to wild type controls (WT), but also increased ventricular dilatation, fibrosis, apoptosis, and 4-week post-MI mortality (64% in AKO vs. 25% in WT, P = 0.02), suggesting a shift toward greater pathologic hypertrophy in the absence of pro-adaptive alpha1A effects. alpha1A-AR knockout increased phospho-p38 levels in the pre-MI myocardium compared to WT (0.55 ± 0.16 vs. 0.03 ± 0.01, P<0.05) but decreased phospho-ERK1/2 post-MI (0.49 ± 0.35 arbitrary units vs. 1.55 ± 0.43 in WT, P<0.05). Furthermore, expression of pro-apoptotic factor Bax was increased (1.19 ± 0.15 vs. 0.78 ± 0.08, P<0.05) and expression of anti-apoptotic factors Bcl2 was decreased (0.26 ± 0.01 vs. 0.55 ± 0.06, P<0.01) compared to WT., Conclusions: Alpha1A-AR provides an important counterbalance to pathologic pathways during post-MI remodeling that may be mediated through ERK1/2 signaling; these observations provide support for further development of an alpha1A-AR/ERK-based molecular intervention for this chronic, often fatal disease.

Background: Dihydroergotamine (DHE) is an acute antimigraine agent that displays affinity for dopamine D 2 -like receptors, serotonin 5-HT 1/2 receptors and α 1 /α 2 -adrenoceptors. Since activation of vascular α 1 /α 2 -adrenoceptors results in systemic vasopressor responses, the purpose of this study was to investigate the specific role of α 1 - and α 2 -adrenoceptors mediating DHE-induced vasopressor responses using several antagonists for these receptors., Methods: For this purpose, 135 male Wistar rats were pithed and divided into 35 control and 100 pretreated i.v. with ritanserin (100 μg/kg; to exclude the 5-HT 2 receptor-mediated systemic vasoconstriction). Then, the vasopressor responses to i.v. DHE (1-3100 μg/kg, given cumulatively) were determined after i.v. administration of some α 1 /α 2 -adrenoceptor antagonists., Results: In control animals (without ritanserin pretreatment), the vasopressor responses to DHE were: (i) unaffected after prazosin (α 1 ; 30 μg/kg); (ii) slightly, but significantly, blocked after rauwolscine (α 2 ; 300 μg/kg); and (iii) markedly blocked after prazosin (30 μg/kg) plus rauwolscine (300 μg/kg). In contrast, after pretreatment with ritanserin, the vasopressor responses to DHE were: (i) attenuated after prazosin (α 1 ; 10 and 30 μg/kg) or rauwolscine (α 2 ; 100 and 300 μg/kg); (ii) markedly blocked after prazosin (30 μg/kg) plus rauwolscine (300 μg/kg); (iii) attenuated after 5-methylurapidil (α 1A ; 30-100 μg/kg), L-765,314 (α 1B ; 100 μg/kg), BMY 7378 (α 1D ; 30-100 μg/kg), BRL44408 (α 2A ; 100-300 μg/kg), imiloxan (α 2B ; 1000-3000 μg/kg) or JP-1302 (α 2C ; 1000 μg/kg); and (iv) unaffected after the corresponding vehicles (1 ml/kg)., Conclusion: These results suggest that the DHE-induced vasopressor responses in ritanserin-pretreated pithed rats are mediated by α 1 - (probably α 1A , α 1B and α 1D ) and α 2 - (probably α 2A , α 2B and α 2C ) adrenoceptors. These findings could shed light on the pharmacological profile of the vascular side effects (i.e. systemic vasoconstriction) produced by DHE and may lead to the development of more selective antimigraine drugs devoid vascular side effects.

Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) remains an elusive disease with the cause for the pain unclear. BPS/IC patients present increased sympathetic activity and high levels of urinary noradrenaline. At the experimental level, it has been shown that chronic adrenergic stimulation produces pain and bladder changes through an alpha 1A adrenoceptor mediated mechanism. Water avoidance stress (WAS) in rodents reproduces signs of nociception and bladder changes seen in BPS/IC patients. In this study, we explore the possible role of alpha 1A adrenoceptor in bladder pain and morphological changes. WAS was induced in a group of female Wistar rats. A separate WAS group received 0.2 mg/kg day silodosin (WAS + S). Lower abdominal pain was determined by performing sensitivity to Von Frey filaments. Bladder reflex activity was determined by cystometry in anaesthetised animals. Urine was collected for noradrenaline quantification by HPLC. Bladders were harvested and stained with Haematoxylin-eosin (to analyse urothelial morphology and to determine the disruption of surface umbrella cells) or with Toluidine Blue 0.1% to analyse mast cell infiltration. WAS increased urinary noradrenaline level and bladder frequency and decreased mechanical pain threshold, which was reversed by silodosin. WAS induced lymphocytic and mast cells infiltration in the mucosa and mild urothelial disruption, which was absent in WAS + S group. Alpha 1A adrenoceptor stimulation has an important role in the appearance of bladder pain in rats. Since BPS/IC patients present high levels of noradrenaline, alpha 1A stimulation may be an additional trigger for bladder dysfunction presented by these patients. Further studies will determine the clinical relevance of this finding in the treatment of BPS/IC patients.

Objective: Hypertension is associated with unfavorable changes in adrenergic receptor responsiveness, but the relationship of race and sex to adrenergic receptor responsiveness in the development of cardiovascular disease is unclear. This study examined α-adrenergic and ß-adrenergic receptor responsiveness in African-American and white men and women with untreated high blood pressure (BP) (HBP) and with normal BP., Methods and Results: The study sample comprised 161 African-American and white men and women in the age range 25-45 years. Isoproterenol, a nonselective ß-adrenergic receptor agonist, was administered intravenously to determine the bolus dose required to increase heart rate by 25 bpm, an index of β-adrenergic receptor responsiveness. Similarly, phenylephrine, an α1-adrenergic receptor agonist, was administered to determine the bolus dose required to increase BP by 25 mmHg, an index of vascular α1-adrenergic receptor responsiveness. HBP (P < 0.01), male sex (P = 0.04), and higher BMI (P < 0.01) were all associated with reduced β-adrenergic receptor responsiveness, with a similar trend observed for African-American race (P = 0.07). Conversely, α1-adrenergic receptor responsiveness was increased in association with HBP (P < 0.01), female sex (P < 0.01), and African-American race (P < 0.01)., Conclusion: In the early stages of hypertension, cardiovascular β-adrenergic receptors demonstrate blunted responsiveness, whereas conversely α1-adrenergic receptors exhibit increased responsiveness. This pattern of receptor changes is especially evident in men and African-Americans, is exacerbated by obesity, and may contribute to the development of cardiovascular disease.

Previously, we showed that the blockade of α1-adrenoreceptors in the median raphe nucleus (MnR) increased food intake in free-feeding rats, indicating that adrenergic mechanisms in the MnR participate in the regulation of food intake. However, the impact of such a pharmacological manipulation on other neural circuits related to food intake remains unknown. In the current study, we sought to identify forebrain regions which are responsive to α1-adrenergic receptor blockade and presumably involved in the modulation of the feeding response. For this purpose, we examined the induction of c-Fos immunoreactivity in forebrain structures following injections of the α1-adrenoceptor antagonist prazosin into the MnR of free-feeding rats. To determine the chemical identity of hypothalamic c-Fos-positive cells, we then conducted double-label immunohistochemistry for Fos/orexin (OX) or Fos/melanin-concentrating hormone (MCH). Finally, we combined anterograde tracing from the MnR with immunohistochemical detection of orexin. Prazosin injections into the MnR significantly increased food intake. The ingestive response was accompanied by an increase in Fos expression in the basolateral amygdala (BLA) and lateral hypothalamic area (LHA). In the LHA, Fos expression occurred in neurons expressing OX, but not MCH. Combined anterograde tracing experiments revealed that LHA OX neurons are prominently targeted by MnR axons. These findings suggest that intra-MnR injection of prazosin, via activation of orexinergic neurons in the LHA and non-orexinergic neurons in the BLA, evoked a motivational response toward food intake., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Purpose: Although studies suggest elevated adrenergic activity paralleling metabolic syndrome in OZRs, the moderate hypertension and modest impact on organ perfusion question the multi-scale validity of these data., Methods: To understand how adrenergic function contributes to vascular reactivity in OZR, we utilized a multi-scale approach to investigate pressure responses, skeletal muscle blood flow, and vascular reactivity following adrenergic challenge., Results: For OZR, adrenergic challenge resulted in increased pressor responses vs LZRs, mediated via α 1 receptors, with minimal contribution by either ROS or NO bioavailability. In situ gastrocnemius muscle of OZR exhibited blunted functional hyperemia, partially restored with α 1 inhibition, although improved muscle performance and VO 2 required combined treatment with TEMPOL. Within OZR in situ cremaster muscle, proximal arterioles exhibited a more heterogeneous constriction to adrenergic challenge, biased toward hyperresponsiveness, vs LZR. This increasingly heterogeneous pattern was mirrored in ex vivo arterioles, mediated via α 1 receptors, with roles for ROS and NO bioavailability evident in hyperresponsive vessels only., Conclusions: These results support the central role of the α 1 adrenoreceptor for augmented pressor responses and elevations in vascular resistance, but identify an increased heterogeneity of constrictor reactivity in OZR that is presently of unclear purpose., (© 2016 John Wiley & Sons Ltd.)

Key Points: Rapid onset vasodilatation (ROV) initiates functional hyperaemia upon skeletal muscle contraction and is attenuated during ageing via α-adrenoreceptor (αAR) stimulation, but it is unknown where this effect predominates in resistance networks. In gluteus maximus muscles of young (4 months) and old (24 months) male C57BL/6 mice, tetanic contraction while observing feed arteries and arterioles initiated ROV, which increased with contraction duration, peaked later in upstream versus downstream vessel branches and was attenuated throughout networks with advanced age. With no effect on muscle force production, inhibiting αARs improved ROV in old mice while activating αARs attenuated ROV in young mice. Modulating ROV through αARs was greater in upstream feed arteries and arterioles compared to downstream arterioles, with α 2 ARs more effective than α 1 ARs. ROV is coordinated along resistance networks and modulated differentially between young and old mice via αARs; with advanced age, attenuated dilatation of upstream branches will restrict muscle blood flow., Abstract: Rapid onset vasodilatation (ROV) in skeletal muscle is attenuated during advanced age via α-adrenoreceptor (αAR) activation, but it is unknown where such effects predominate in the resistance vasculature. Studying the gluteus maximus muscle (GM) of anaesthetized young (4 months) and old (24 months) male C57BL/6 mice, we tested the hypothesis that attenuation of ROV during advanced age is most effective in proximal branches of microvascular resistance networks. Diameters of a feed artery (FA) and first- (1A), second- (2A) and third- (3A) order arterioles were studied in response to single tetanic contractions (100 Hz, 100-1000 ms). ROV began within 1 s and peaked sooner in 2A and 3A (∼3 s) than in 1A or FA (∼4 s). Relative amplitudes of dilatation increased with contraction duration and with vessel branch order (FA<1A<2A<3A). In old mice, attenuation of ROV was greater in FA and 1A compared to 2A and 3A. With no effect on muscle force production, inhibiting αARs (phentolamine; 10 -6  m) improved ROV in FA and 1A of old mice while subthreshold stimulation of αARs in young mice (noradrenaline; 10 -9  m) depressed ROV most effectively in FA and 1A. In young mice, stimulating α 1 ARs (phenylephrine; 10 -7  m) and α 2 ARs (UK 14304; 10 -7  m) attenuated ROV primarily in FA. In old mice, inhibiting α 2 ARs (rauwolscine; 10 -7  m) restored ROV more effectively in FA and 1A than did inhibiting α 1 ARs (prazosin; 10 -8  m). We conclude that, with temporal and spatial coordination along resistance networks, attenuation of ROV with advanced age is most effective in proximal branches via constitutive activation of α 2 ARs., (© 2016 The Authors. The Journal of Physiology © 2016 The Physiological Society.)

The first part of the review presents data on localization of alpha 1-adrenoceptor (AR) in the heart, including plasma and nuclear membranes, on its relative concentrations in the myocardium, on three alpha1-AR (A-, B- and D-) subtypes, the two of which (A and B) are mainly expressed in the human and mouse myocardium and all the three subtypes are expressed in rat''s myocardium. It also reports that the activation of alpha 1-AR induces inotropic effect (positive, negative or biphasic), luzitropic effect, chronotropic effect (the latter can be also positive or negative), and arrhythmogenic effects. The review provides information on the mechanisms forming the basis of these effects, including the role of G q- and G i-proteins, individual isoforms of phospholipase C, phosphatidylinositol 3-kinase, phosphatidylinositol 4,5-biphosphate, diacylglycerol, inositol triphosphate, protein kinase C, protein kinase D, NO-synthase and ion channels. It discusses the literature data on the role of individual subtypes of alpha 1-AR in the implementation of these effects. It reports on the stability of alpha1-AR to desensitization, which is important for the realization by the receptors of their trophic function.

Background: Acute cocaine withdrawal syndrome (ACWS) is characterized as a set of organic alterations triggered by abrupt discontinuation of chronic cocaine consumption, usually occurring at 24-40 hours after withdrawal. However, little is known about the relationship between central and peripheral sympathetic neurotransmission during ACWS., Objective and Methods: We investigated the mechanisms involved in central and peripheral sympathetic neurotransmission and how ACWS affects the sympathetic functionality. Cocaine was administered twice daily for 5 days in Wistar rats (at least 5 in each group): on the first and second day, 15 mg/kg/i.p.; third day, 20 mg/kg/i.p.; and finally in the last two days, 30 mg/kg/i.p. Subsequently, at 1, 24, 48 and 120 h after cocaine administration the following experiments were done: (i) at the central level, behavioral tests of open-field and elevated plus maze; and (ii) at the peripheral level, tests of catecholamine release, function of α2-adrenergic receptors (α2-ARs), imidazoline receptors (I(1,2)-Rs), L-type voltage-gated (Ca(v1.2)) Ca(2+) channels and α1-ARs., Results: During ACWS, rats showed hypolocomotion and exacerbation of anxiogenic-effects 24 h after cocaine withdrawal. Likewise, a decrease in the catecholamine release and activity of α2-ARs/I(1,2)-Rs at 24-48 h after cocaine withdrawal was observed. A decrease in Ca(v1.2) channels and α1-ARs function at 48 h after cocaine withdrawal was observed., Conclusions: The relationship of central and peripheral sympathetic neurotransmission during ACWS possibly due to a failure in activation and/or inactivation of presynaptic α2-ARs/I(1,2)-Rs, may offer a potential target for attenuating ACWS.

Ca(2+)/calmodulin-dependent calcineurin (CaN) plays an important role in various Ca(+2) signaling pathways, among which are those involved in cardiac diseases. It has also been shown that a heightened sympathetic tone accelerates the development of heart failure. The present study investigates whether the CaN-mediated nuclear factor of activated T-cells (NFAT) pathway is involved in cultured neonatal rat cardiac fibroblast proliferation induced by phenylephrine. CF proliferation was assessed by a cell survival assay and cell counts. Green fluorescent protein-tagged NFAT3 was used to determine the cellular location of NFAT3. CaN activity and protein levels were also determined by an activity assay kit and Western blotting, respectively. Results showed that phenylephrine promoted CF proliferation, which was abolished by α1-adrenergic receptor antagonist (prazosin), a blocker of Ca(+2) influx (nifedipine), an intracellular Ca(2+) buffer (BAPTA-AM), CaN inhibitors (cyclosporin A and FK506), and over-expression of dominant negative CaN. Phenylephrine activated CaN and evoked NFAT3 nuclear translocation, both of which were blocked by cyclosporine A (CsA) or over-expression of dominant negative CaN. These results suggest that the Ca(2+)/CaN/NFAT pathway mediates PE-induced CF proliferation, and this pathway might be a possible therapeutic target in cardiac fibrosis.

Aims: Testicular capsule contractile dysfunctions are recognized to contribute to male infertility, but the influence of sexual maturation and exogenous testosterone on the expression and function of androgen receptor and α1-adrenoceptors on rat testicular capsule is unclear. Here, these two biological parameters were evaluated on testicular capsule from sexually immature and young adult rats treated or not with exogenous testosterone., Main Methods: Male Wistar rats (45- and 60-day-old) were assigned into groups: control (saline 0.9%) or testosterone-treated (propionate testosterone). Testicular capsule was isolated and processed for functional studies, immunohistochemistry, Western blot and RT-PCR studies., Key Findings: Relative testicular capsule wet weight was not affected by sexual maturation or exogenous testosterone treatment. The expression and immunolocalization of androgen receptor (mRNA and protein) was identified in testicular capsule. Androgen receptor and α1-adrenoceptor (Adra1a, Adra1b, and Adra1d) mRNA levels were similar in testicular capsule from all experimental groups. Functional studies indicated that contractions produced by noradrenaline in testicular capsule from 45- and 60-day-old rats treated or not with testosterone were mainly mediated by α1A- and α1B-adrenoceptors. The L-type Ca(2+) channel blocker nifedipine induced a higher inhibitory effect on noradrenaline induced contractions in testicular capsule from 45- than 60-day-old rats treated with testosterone., Significance: Molecular studies, immunohistochemistry and pharmacological functional assays used in this study provide evidences of the androgen receptor expression in testicular capsule and that function, and not mRNA and protein expression levels of the α1-adrenoceptor subtypes in this tissue, is differentially influenced by the rat androgen status., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Transient receptor potential vanilloid 1 (TRPV1) is involved in sensory nerve nociceptive signaling. Recently, it has been discovered that TRPV1 receptors also regulate basal body temperature in multiple species from mice to humans. In the present study, we investigated whether TRPV1 modulates basal sympathetic nervous system (SNS) activity. C57BL6/J wild-type (WT) mice and TRPV1 knockout (KO) mice were implanted with radiotelemetry probes for measurement of core body temperature. AMG9810 (50 mg/kg) or vehicle (2% DMSO/5% Tween 80/10 ml/kg saline) was injected intraperitoneally. Adrenoceptor antagonists or vehicle (5 ml/kg saline) was injected subcutaneously. In WT mice, the TRPV1 antagonist, AMG9810, caused significant hyperthermia, associated with increased noradrenaline concentrations in brown adipose tissue. The hyperthermia was significantly attenuated by the β-adrenoceptor antagonist propranolol, the mixed α-/β-adrenoceptor antagonist labetalol, and the α1-adrenoceptor antagonist prazosin. TRPV1 KO mice have a normal basal body temperature, indicative of developmental compensation. d-Amphetamine (potent sympathomimetic) caused hyperthermia in WT mice, which was reduced in TRPV1 KO mice, suggesting a decreased sympathetic drive in KOs. This study provides new evidence that TRPV1 controls thermoregulation upstream of the SNS, providing a potential therapeutic target for sympathetic hyperactivity thermoregulatory disorders., (© FASEB.)

Cardiac hypertrophy is a complex remodeling process of the heart induced by physiological or pathological stimuli resulting in increased cardiomyocyte size and myocardial mass. Whereas cardiac hypertrophy can be an adaptive mechanism to stressful conditions of the heart, prolonged hypertrophy can lead to heart failure which represents the primary cause of human morbidity and mortality. Among G protein-coupled receptors, the α1-adrenergic receptors (α1-ARs) play an important role in the development of cardiac hypertrophy as demonstrated by numerous studies in the past decades, both in primary cardiomyocyte cultures and genetically modified mice. The results of these studies have provided evidence of a large variety of α1-AR-induced signaling events contributing to the defining molecular and cellular features of cardiac hypertrophy. Recently, novel signaling mechanisms have been identified and new hypotheses have emerged concerning the functional role of the α1-adrenergic receptors in the heart. This review will summarize the main signaling pathways activated by the α1-AR in the heart and their functional implications in cardiac hypertrophy., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The aim of the present study was to define the role of testicular α1-adrenergic receptors (α1-ADRs) in stress-triggered adaptation of testosterone-producing Leydig cells of adult rats. Results showed that in vivo blockade of testicular α1-ADRs prevented partial recovery of circulating androgen levels registered after 10× repeated immobilization stress (10 × IMO). Moreover, α1-ADR-blockade diminished 10 × IMO-triggered recovery of Leydig cell androgen production, and abolished mitochondrial membrane potential recovery. In the same cells, 10 × IMO-induced increase in Star transcript was abolished, Lhcgr transcript decreased, while transcription of other steroidogenic proteins was not changed. α1-ADR-blockade recovered stress-induced decrease of Nur77, one of the main steroidogenic stimulator, while significantly reduced 10 × IMO-increased in the transcription of the main steroidogenic repressors, Arr19 and Dax1. In vitro experiments revealed an adrenaline-induced α1-ADR-mediated decrease in Nur77 transcription in Leydig cells. Adrenaline-induced increase of repressor Dax1 also involves ADRs in Leydig cells. Accordingly, α1-ADRs participate in some of the stress-triggered effects on the steroidogenic machinery of Leydig cells., (Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.)

The in vivo effect of continuous angiotensin II (Ang II) infusion on arterial blood pressure, vascular hypertrophy and α1 -adrenoceptors (α1 -ARs) expression was explored. Alzet(®) minipumps filled with Ang II (200 ng kg(-1)  min(-1) ) were subcutaneously implanted in male Wistar rats (3 months-old). Groups of rats were also treated with losartan, an AT1 R antagonist, or with BMY 7378, a selective α1D -AR antagonist. Blood pressure was measured by tail-cuff; after 2 or 4 weeks of treatment, vessels were isolated for functional and structural analyses. Angiotensin II increased systolic blood pressure. Phenylephrine-induced contraction in aorta was greater (40% higher) in Ang II-treated rats than in the controls, and similar effect occurred with KCl 80 mm. Responses in tail arteries were not significantly different among the different groups. Angiotensin II decreased α1D -ARs without modifying the other α1 -ARs and induced an increase in media thickness (hypertrophy) in aorta, while no structural change occurred in tail artery. Losartan prevented and reversed hypertension and hypertrophy, while BMY 7378 prevented and reversed the aorta's hypertrophic response, without preventing or reversing hypertension. Findings indicate that Ang II-induced aortic hypertrophic response involves Ang II-AT1 Rs and α1D -ARs. Angiotensin II-induced α1D -AR-mediated vascular remodeling occurs independently of hypertension. Findings identify a α1D -AR-mediated process whereby Ang II influences aortic hypertrophy independently of blood pressure elevation., (© 2016 John Wiley & Sons Ltd.)

α1-Adrenoceptor stimulation of mouse aorta causes intracellular Ca(2+) release from sarcoplasmic reticulum Ca(2+) stores via stimulation of inositoltriphosphate (IP3) receptors. It is hypothesized that this Ca(2+) release from the contractile and IP3-sensitive Ca(2+) store is under the continuous dynamic control of time-independent basal Ca(2+) influx via L-type voltage-gated Ca(2+) channels (LCC) residing in their window voltage range. Mouse aortic segments were α1-adrenoceptor stimulated with phenylephrine in the absence of external Ca(2+) (0Ca) to measure phasic isometric contractions. They gradually decreased with time in 0Ca, were inhibited with 2-aminoethoxydiphenyl borate, and declined with previous membrane potential hyperpolarization (levcromakalim) or with previous inhibition of LCC (diltiazem). Former basal stimulation of LCC with depolarization (15 mM K(+)) or with BAY K8644 increased the subsequent phasic contractions by phenylephrine in 0Ca. Although exogenous NO (diethylamine NONOate) reduced the phasic contractions by phenylephrine, stimulation of endothelial cells with acetylcholine in 0Ca failed to attenuate these phasic contractions. Finally, inhibition of the basal release of NO with N(Ω)-nitro-L-arginine methyl ester also attenuated the phasic contractions by phenylephrine. Results indicated that α1-adrenoceptor stimulation with phenylephrine causes phasic contractions, which are controlled by basal LCC and endothelial NO synthase activity. Endothelial NO release by acetylcholine was absent in 0Ca. Given the growing interest in the active regulation of arterial compliance, the dependence of contractile SR Ca(2+) store-refilling in basal conditions on the activity of LCC and basal eNOS may contribute to a more thorough understanding of physiological mechanisms leading to arterial stiffness., (Copyright © 2015. Published by Elsevier B.V.)

Background: Atrial fibrillation (AF) is the most common arrhythmias among old people. It causes serious long-term health problems affecting the quality of life. It has been suggested that the autonomic nervous system is involved in the onset and maintenance of AF in human. However, investigation of its pathogenesis and potential treatment has been hampered by the lack of suitable AF models in experimental animals., Objectives: Our aim was to establish a long-lasting AF model in mice. We also investigated the role of adrenergic receptor (AR) subtypes, which may be involved in the onset and duration of AF., Methods and Results: Trans-esophageal atrial burst pacing in mice could induce AF, as previously shown, but with only a short duration (29.0 ± 8.1 sec). We found that adrenergic activation by intraperitoneal norepinephrine (NE) injection strikingly increased the AF duration. It increased the duration to more than 10 minutes, i.e., by more than 20-fold (656.2 ± 104.8 sec; P<0.001). In this model, a prior injection of a specific β1-AR blocker metoprolol and an α1-AR blocker prazosin both significantly attenuated NE-induced elongation of AF. To further explore the mechanisms underlying these receptors' effects on AF, we assessed the SR Ca(2+) leak, a major trigger of AF, and consequent spontaneous SR Ca(2+) release (SCR) in atrial myocytes. Consistent with the results of our in-vivo experiments, both metoprolol and prazosin significantly inhibited the NE-induced SR Ca(2+) leak and SCR. These findings suggest that both β1-AR and α1-AR may play important roles in the development of AF., Conclusions: We have established a long-lasting AF model in mice induced by adrenergic activation, which will be valuable in future AF study using experimental animals, such as transgenic mice. We also revealed the important role of β1- and α1-AR-mediated signaling in the development of AF through in-vivo and in-vitro experiments.

Key Points: During exercise there is a balance between vasoactive factors that facilitate increases in blood flow and oxygen delivery to the active tissue and the sympathetic nervous system, which acts to limit muscle blood flow for the purpose of blood pressure regulation. Functional sympatholysis describes the ability of contracting skeletal muscle to blunt the stimulus for vasoconstriction, yet the underlying signalling of this response in humans is not well understood. We tested the hypothesis that activation of inwardly rectifying potassium channels and the sodium-potassium ATPase pump, two potential vasodilator pathways within blood vessels, contributes to the ability to blunt α1 -adrenergic vasoconstriction. Our results show preserved blunting of α1 -adrenergic vasconstriction despite blockade of these vasoactive factors. Understanding this complex phenomenon is important as it is impaired in a variety of clinical populations., Abstract: Sympathetic vasoconstriction in contracting skeletal muscle is blunted relative to that which occurs in resting tissue; however, the mechanisms underlying this 'functional sympatholysis' remain unclear in humans. We tested the hypothesis that α1 -adrenergic vasoconstriction is augmented during exercise following inhibition of inwardly rectifying potassium (KIR ) channels and Na(+) /K(+) -ATPase (BaCl2  + ouabain). In young healthy humans, we measured forearm blood flow (Doppler ultrasound) and calculated forearm vascular conductance (FVC) at rest, during steady-state stimulus conditions (pre-phenylephrine), and after 2 min of phenylephrine (PE; an α1 -adrenoceptor agonist) infusion via brachial artery catheter in response to two different stimuli: moderate (15% maximal voluntary contraction) rhythmic handgrip exercise or adenosine infusion. In Protocol 1 (n = 11 subjects) a total of six trials were performed in three conditions: control (saline), combined enzymatic inhibition of nitric oxide (NO) and prostaglandin (PG) synthesis (l-NMMA + ketorolac) and combined inhibition of NO, PGs, KIR channels and Na(+) /K(+) -ATPase (l-NMMA + ketorolac + BaCl2  + ouabain). In Protocol 2 (n = 6) a total of four trials were performed in two conditions: control (saline), and combined KIR channel and Na(+) /K(+) -ATPase inhibition. All trials occurred after local β-adrenoceptor blockade (propranolol). PE-mediated vasoconstriction was calculated (%ΔFVC) in each condition. Contrary to our hypothesis, despite attenuated exercise hyperaemia of ∼30%, inhibition of KIR channels and Na(+) /K(+) -ATPase, combined with inhibition of NO and PGs (Protocol 1) or alone (Protocol 2) did not enhance α1 -mediated vasoconstriction during exercise (Protocol 1: -27 ± 3%; P = 0.2 vs. control, P = 0.4 vs. l-NMMA + ketorolac; Protocol 2: -21 ± 7%; P = 0.9 vs. control). Thus, contracting human skeletal muscle maintains the ability to blunt α1 -adrenergic vasoconstriction during combined KIR channel and Na(+) /K(+) -ATPase inhibition., (© 2015 The Authors. The Journal of Physiology © 2015 The Physiological Society.)