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Monoamine neurotransmitters are released by specialized neurons that regulate behavioral and cognitive functions. Although localization of monoaminergic neurons in the brain is well known, the distribution, concentration, and kinetics of monoamines remain unclear. We used mass spectrometry imaging (MSI) for simultaneous and quantitative imaging of endogenous monoamines to generate a murine brain atlas of serotonin (5-HT), dopamine (DA), and norepinephrine (NE) levels. We observed several nuclei rich in both 5-HT and a catecholamine (DA or NE). Additionally, we analyzed de novo monoamine synthesis or fluctuations in those nuclei. We propose that MSI is a useful tool to gain deeper understanding of associations among the localization, levels, and turnover of monoamines in different brain areas and their role in inducing behavioral changes.

Angiotensin II (Ang II) is an intrinsic peptide having strong vasopressor effects, and thus, it plays an important role in the physiological regulation of blood pressure. The vasopressor effects of Ang II include direct contraction of myocardium and vascular smooth muscles (SMs) along with aldosterone-mediated sodium retention. In addition, indirect vascular contractions induced by noradrenaline (NA), the release of which is mediated through Ang II receptor type 1 (AT 1 ) existing at the sympathetic nerve terminals (SNTs), also contribute to the vasopressor effects of Ang II. Stimulation of NA release from SNTs by Ang II also occurs in the myocardium leading to an increase in heart rate and cardiac contraction. Furthermore, Ang II enhances the contractions of non-vascular SMs, such as vas deferens, through induction of NA release from the SNTs. We have found that Ang II attenuated vagus nerve stimulation-induced bradycardia in a losartan-sensitive manner. This suggests that Ang II attenuates vagus nerve stimulation-induced bradycardia by inhibiting acetylcholine (ACh) release from the parasympathetic nerve terminals (PNTs) through activation of the AT 1 receptor. Ang II was also reported to attenuate the release of ACh from the PNTs in SMs, such as stomach and airway, thus suppressing their contractile functions. There are, however, conflicting reports of the effects of Ang II on parasympathetic nerve-mediated contractile regulation of SMs. In this review, we have highlighted the relevant research articles including our experimental reports on the regulation of sympathetic and parasympathetic nerve-mediated excitation and contraction by Ang II along with the future prospects.

Selective sodium glucose transporter-2 inhibitor (SGLT2i) treatment promotes urinary glucose excretion, thereby reducing blood glucose as well as body weight. However, only limited body weight reductions are achieved with SGLT2i administration. Hyperphagia is reportedly one of the causes of this limited weight loss. However, the effects of SGLT2i on systemic energy expenditure have not been fully elucidated. We investigated the acute effects of dapagliflozin, an SGLT2i, on systemic energy expenditure in mice. Eighteen hours after dapagliflozin administration, oxygen consumption and brown adipose tissue (BAT) expression of ucp1, a thermogenesis-related gene, were significantly decreased as compared with those after vehicle administration. In addition, dapagliflozin significantly suppressed norepinephrine (NE) turnover in BAT and c-fos expression in the rostral raphe pallidus nucleus (rRPa), which contains the sympathetic premotor neurons responsible for thermogenesis. These findings indicate that the dapagliflozin-mediated acute decrease in energy expenditure involves a reduction in BAT thermogenesis via decreased sympathetic nerve activity from the rRPa. Furthermore, common hepatic branch vagotomy abolished the reductions in ucp1 expression, NE contents in BAT, and c-fos expression in the rRPa. In addition, alterations in hepatic carbohydrate metabolism, such as decreases in glycogen contents and upregulation of phosphoenolpyruvate carboxykinase, occurred prior to the suppression of BAT thermogenesis, e.g., 6 h after dapagliflozin treatment. Collectively, these results suggest that SGLT2i acutely suppresses energy expenditure in BAT via regulation of an interorgan neural network consisting of the common hepatic vagal branch and sympathetic nerves.

In the human genome, there are approximately 30 LTR retrotransposon-derived genes, such as the sushi-ichi retrotransposon homologues (SIRH) and the paraneoplastic Ma antigen (PNMA) family genes. They are derivatives from the original LTR retrotransposons and each gene seems to have its own unique function. PEG10/SIRH1 as well as PEG11/RTL1/SIRH2 and SIRH7/LDOC1 play essential roles in placenta formation, maintenance of fetal capillaries and the differentiation/maturation of a variety of placental cells, respectively. All of this evidence provides strong support for their contribution to the evolution of viviparity in mammals via their eutherian-specific functions. SIRH11/ZCCHC16 is an X-linked gene that encodes a CCHC type of zinc-finger protein that exhibits high sequence identity to the LTR retrotransposon Gag protein and its deletion causes abnormal behavior related to cognition, including attention, impulsivity and working memory, possibly via the locus coeruleus noradrenaergic system in mice. Therefore, we have suggested that the acquisition of SIRH11/ZCCHC16 was involved in eutherian brain evolution. Interestingly, SIRH11/ZCCHC16 displays lineage-specific structural and putative species-specific functional variations in eutherians, suggesting that it contributed to the diversification of eutherians via increasing evolutionary fitness by these changes.

This review describes my research for the past 39 years regarding the pharmacology of pain and analgesia. We have demonstrated that the descending noradrenergic system is involved in the analgesic effect of morphine injected into the nucleus reticularis gigantocellularis, and that noradrenaline exerts antinociception mediated by α-adrenoceptors. We have found that noxious mechanical and thermal stimuli to the skin increase the release of substance P and somatostatin, respectively, from the dorsal horn in situ, and that noradrenaline inhibits the release of substance P and glutamate from primary afferents. We developed an animal model of cancer pain using melanoma cells. We have shown that the suppression of cancer pain results in the inhibition of tumor growth and lung metastasis, and that melanoma cells release several algogenic substances including ATP, endothelin-1, and bradykinin. We investigated neuropathic allodynia induced by the chemotherapeutic drugs paciltaxel, oxaliplatin, vincristine, and bortezomib. Single administration of these drugs caused allodynia with similar time-courses. However, antiallodynic actions of adjuvant analgesics, including gabapentin and limaprost, were dependent on the chemotherapeutic drugs used. Limaprost experiments have revealed that a decrease in peripheral blood flow is involved in allodynia exacerbation after the administration of paciltaxel and oxaliplatin. We have developed animal models of herpetic pain and postherpetic neuralgia using herpes simplex virus 1. We have demonstrated that nitric oxide, prostaglandin E2, and galectin-3 are involved in herpetic allodynia, that risk factors associated with postherpetic allodynia include severe herpetic pain, nociceptin, and major histocompatibility complex, and that deafferentation and nitric oxide are involved in postherpetic allodynia.

Hot flash (HF) is the most common phenomenon in climacteric symptoms which often develop concomitantly with a decrease in estrogen in postmenopausal women. The onset mechanism of the hot flash is complicated and remains unclear. To date, some animal models of postmenopausal HF have been devised, but they are not fully available because of the difficulty in producing them. It is thought that hyperactivity of the central α-adrenergic system with a decrease in estrogen participates in the onset of postmenopausal HF. Therefore, in the present study, we examined whether a HF model could be easily produced by administering yohimbine (YOH), a presynaptic α₂-adrenoceptor antagonist which promotes norepinephrine release, to female rats. HF-like symptoms such as a rise in tail skin temperature and a fall in rectal temperature were shown in the rats who received YOH (3 mg/kg) subcutaneously seven days after the ovariectomy (OVX). Such symptoms following YOH administration were observed in sham rats as well, but were much more clearly noted in OVX rats. We next examined the effects of various drugs, which are clinically effective against postmenopausal HF, on HF-like symptoms in YOH-treated OVX rats: clonidine, a presynaptic α₂-adrenoceptor agonist which inhibits norepinephrine release; β-estradiol as an estrogen; and Keishibukuryogan, a Kampo medicine. These drugs inhibited HF-like symptoms in YOH-treated OVX rats. These results suggest that the activity of the α-adrenergic system is enhanced with a decrease in estrogen in OVX rats whereby YOH causes HF-like symptoms more conspicuously than in sham rats. Therefore, it is thought that YOH-treated OVX rats will be a novel and simple model of postmenopausal HF.

The development of antidepressant started from 1950's and it is based on monoamine hypothesis. Antidepressants enhance monoamine, such as serotonin, nor adrenaline and dopamine neurotransmission by blockade of monoamine transporter or monoamine oxydase. The antidepressants under clinical trials enhance those monoamine in various combinations. The development of newer antidepressants is still on pre-clinical trials. Those candidates such as neurotrophic factors and neuropeptides may show antidepressant effect without monoamine hypothesis and those are expected to overcome the limitation of existing antidepressant.

The sleep-wake cycle is regulated by interaction between monoaminergic, cholinergic and GABAergic neuronal activities. Monoaminergic neurons including noradrenergic (locus coeruleus: LC), histaminergic (tuberomammillary nucleus) and serotonergic (raphe nuclei) neurons projected diffusely to the cerebrocortex, thalamus and brainstem are known as the center of sleep regulation. Interestingly, although the cell bodies displaying prepro-orexin (prepro-OX) immunoreactivity are limited to the hypothalamus, OXergic neurons densely project to LC, tuberomammillary nucleus and raphe nuclei. These evidences suggest a link between monoaminergic and OXergic neurons. We found that OXA and B evoke norepinephrine release from rat cerebrocortical slices but histamine and serotonin releases are not evoked. All noradrenergic projections to cerebrocortex originate from the LC. Thus, the main link between OXergic and monoaminergic neurons may be noradrenergic in the cerebral cortex. Therefore, we have studied OXergic-noradrenergic neurons and anesthesia. We found that OXs reduced anesthesia time, which was reversed by SB334867 (OX1-receptor antagonist). However, as alpha2-receptor ligands did not affect OXs-norepinephrine release from cerebrocortical slices, alpha2-receptors may not be involved in OXergic-noradrenergic neurons in the cerebral cortex. Bicuculline (GABAA-receptor antagonist) could not reverse inhibitory effects of barbiturates on OXs-norepinephrine release but significantly reversed these effects on K+-evoked release. Moreover, muscimol (GABAA-receptor agonist) did not inhibit the OX-norepinephrine release but inhibited the K+-evoked release. Therefore, GABAA-receptor may also not be involved.

Effects of milnacipran (MIL), a selective serotonin and noradrenaline (NA) reuptake inhibitor, on the neuronal excitability and synaptic transmission in the rat locus coeruleus (LC) were examined by intracellular and whole-cell patch-clamp recording techniques. We compared MIL and methylphenidate (MPH), a selective NA and dopamine reuptake inhibitor, as a therapeutic agent for attention deficit/hyperactivity disorder. Application of MPH (1-100 microM) and MIL (1-100 microM) to artificial cerebrospinal fluid (ACSF) produced a hyperpolarizing response in LC neurons in a concentration-dependent manner. Spontaneous firing of LC neurons was blocked during the hyperpolarization. The MIL-induced hyperpolarization was blocked by yohimbine (1 microM), an antagonist for alpha-adrenoceptors. These results suggest that the MIL-induced hyperpolarization is mediated by NA via alpha2-adrenoceptors in LC neurons. Under the whole-cell patch-clamp condition, prolonged application of MIL produced an outward current which lasted as long as MIL existed in the ACSF. The outward current induced by NA was enhanced by MIL in LC neurons. MIL enhanced the amplitude and duration of the inhibitory postsynaptic potential, while it depressed the excitatory postsynaptic potential. The results indicated that both MIL and MPH showed almost the same effects on neuronal activity and synaptic transmission in the rat LC. These results suggest that MIL increases the concentration of NA at synaptic clefts by inhibiting the NA reuptake system in the rat LC.

Brain microdialysis has become a well established and a widely-used technique for in vivo measurement of extracellular levels of neurotransmitters. However, a single neurotransmitter in the perfusates has been measured in most studies. The present paper describes a simultaneous measurement of serotonin and dopamine release in the prefrontal cortex of mice. Using this technique, we examined the modulation by serotonin(1A) receptors of serotonin, dopamine, and noradrenaline release in the cortex of isolation-reared mice. The isolation-reared mouse is a useful model of complicated mood disorders including phenotypes of anxiety, depression, and aggression. The study shows that isolation rearing selectively decreases the sensitivity of serotonin(1A) receptors to increase dopamine release.

This review article focuses on the suppression of sensory transmission by inhalational anesthetics at the spinal cord level. Volatile anesthetics (e.g. halothane and isoflurane) suppress neuronal responses evoked by both noxious and non-noxious stimuli. This suppression is mediated largely by activation of GABAA and glycine receptors systems in the spinal dorsal horn. Depression of spinal glutamate receptor systems is also probably involved. The analgesic action of nitrous oxide is produced by activation of supra-spinal descending inhibitory systems, not by direct action on the spinal cord. Activation of the descending inhibitory systems by nitrous oxide causes release of noradrenaline in the spinal dorsal horn, and activates alpha 2 adrenergic receptor systems, resulting in depression of neuronal responses evoked by noxious stimuli. GABAA and glycine receptor systems in the spinal dorsal horn are also important components of nitrous oxide anesthesia in depressing neuronal responses evoked by non-noxious stimuli. Although excitation or inhibition of GABAA, glycine, alpha 2 adrenergic and glutamate receptors systems is an important action of inhalational anesthetics, influence of inhalational anesthetics on interactions among these receptor systems has yet to be studied.

Most antidepressants used in Japan are reuptake inhibitors of monoamine, such as noradrenaline and serotonin. Incidence of refractory depression, which is resistant to at least two monoamine reuptake inhibitors, is 10-20%. ECT and the addition of lithium, thyroid hormones or dopamine agonists is used for the treatment of refractory depression. Bupropion and MAO inhibitors are also effective for refractory depression but not approved in Japan. The presynaptic mechanism of action of these antidepressants has been studied by in vivo microdialysis studies. Serotonin reuptake inhibitors increase extracellular serotonin concentrations in the brain. Noradrenaline reuptake inhibitors increase extracellular noradrenaline concentrations in the brain, and increase extracellular dopamine concentrations in the frontal cortex, but not in the nucleus accumbens or striatum. ECT and MAO inhibitors increase extracellular serotonin concentrations in the brain, and ECT, bupropion and MAO inhibitors increase extracellular noradrenaline concentrations in the brain. In contrast to monoamine reuptake inhibitors, ECT, bupropion and MAO inhibitors increase extracellular dopamine concentrations not only in the frontal cortex but also in the nucleus accumbens and striatum. The facilitation of mesolimbic or nigrostriatal dopamine neurotransmission may be the mechanism of action behind these treatments' efficacies for refractory depression. Although there are only a few studies concerning the mechanism of action of augmentation therapy, recent studies demonstrated that subchronic lithium treatment increases basal concentrations of extracellular serotonin in the frontal cortex and hippocampus. Subchronic lithium further increases SSRI-induced increases in extracellular serotonin concentrations, and this effect is suggested to be the mechanism of action for lithium augmentation of antidepressants.

Background: NMDA receptor contributes to cause neuronal death in anoxic condition. It is not known how a part of NMDA receptors, NMDA-binding site and/or glycine-binding site, influence neuronal damage in rats' hippocampus in vitro., Methods: Rats' hippocampus, labeled with norepinephrine (3H-NE), was incubated in artificial cerebrospinal fluid (aCSF) and we measured 3H-NE in superfusion solution and remaining tissue. Glucose was eliminated from aCSF and 95% N2 + 5% CO2 produced the anoxic state., Results: The amount of 3H-NE release increased in anoxia with NMDA (NMDA-binding site agonist), while there was no influence on NMDA receptor in non-anoxic state even after D-serine (glycine-binding site agonist) has been administered. The 3H-NE was released more when D-serine (100 mu mM) and NMDA (100 mu mM) were administered together than when only D-serine (10 mu mM, 100 mu mM, 1000 mu mM) in anoxia or NMDA (10 mu mM, 100 mu mM, 1000 mu mM) in anoxia was administered., Conclusion: Glycine-binding site agonist alone does not act significantly but ion channels in NMDA receptor open more and become more effective when both glycine-binding site agonist and NMDA-binding site agonist exist, suggesting that there are interactions between NMDA-binding site and glycine-binding site in NMDA-receptor during anoxia.

Double-peaked vasoconstrictor responses to periarterial nerve electrical stimulation (PNS) were readily induced in the condition of 30-s trains of pulses in isolated, perfused canine splenic artery, using the cannula insertion technique. P2X purinoceptors have been shown to be involved mainly in the 1st peaked response and alpha 1 adrenoceptors mostly in the 2nd one. Administrated NPY induced no direct vasoconstriction or only a slight vasoconstriction, and it inhibited the double-peaked vasoconstriction in a dose-related manner. A small dose of NPY Y1-receptor agonist, L-P NPY, readily potentiated the 2nd peaked response to PNS, and an increasing dose of LP-NPY did both the 1st and 2nd peaked responses. The 2nd peaked response was significantly inhibited by treatment with chloroethylclonidine (CEC), an alpha 1B-adrenoceptor antagonist, but the 1st peaked response was not influenced. On the other hand, an alpha 1A-antagonist, WB4101, rather potentiated the 2nd peaked response, although it did not modify the 1st one. Administered NA-induced constrictions were consistently inhibited by WB4101 but not by CEC. From these results, it is concluded that NPY inhibits the release of ATP and NA from periarterial nerve terminals by activation of presynaptic NPY Y2 receptors, and it potentiates PNS-induced vasoconstrictions via alpha 1B-adrenoceptors by activation of postjunctional NPY Y1 receptors in the canine splenic artery.

The sympathetic nervous system regulates cardiovascular function by activating adrenergic receptors which are known to have a critical role in regulating transmitter release from sympathetic nerves and from adrenergic neurons in the central nervous system. alpha 2A adrenergic receptor knockout mouse (alpha 2A-KO) showed an increase in sympathetic activity with resting tachycardia, depletion of cardiac tissue norepinephrine concentration. Knockout mouse study reveals that the alpha 2B adrenoceptor (alpha 2B AR) mediates the hypertensive response, and the alpha 2A AR mediates the hypotensive response, induced by alpha 2 agonists. Both the alpha 2A and alpha 2C AR subtypes are required for normal presynaptic control of transmitter release from sympathetic nerves. alpha 2A AR subtype inhibits transmitter release at high stimulation frequencies, whereas the alpha 2C AR subtype modulates neurotransmission at lower levels of nerve activity. Salt-induced hypertension experiment using alpha 2B-KO and alpha 2C-KO revealed that alpha 2B AR subtype is necessary to raise BP in response to dietary salt loading. Lack of adequately functional renal alpha 2B AR is thought to preclude reabsorption of sodium. alpha 1B-KO study revealed that alpha 1B AR is a mediator of the blood pressure response and the aorta contractile response induced by alpha 1 agonists.

The kidney contributes to cardiovascular homeostasis through Na+ and water excretion and renin secretion. Changes in renal functions, therefore, have a close relationship to pathophysiology of cardiovascular diseases and to drug efficacy for them. The functions of the kidney are controlled by the sympathetic nervous system and various kinds of humoral factors and by their complicated interactions. Studies in the intact and working kidney in vivo have been providing physiologically significant information on the renal functions and drug actions. This review, by demonstrating data obtained in our laboratory with experiments in anesthetized dogs in vivo, refers mainly to the neural control of renal functions and renal actions of atrial natriuretic peptide (ANP) and an adenylate cyclase activator NKH477, either of which could be used for the treatment of congestive heart failure. Electrical stimulation of the renal nerves, which could mimic the events during elevation of renal sympathetic nerve activity, induces frequency-dependent renal norepinephrine release, renal vasoconstriction, antinatriuresis and renin secretion. ANP causes potent natriuresis and suppresses the nerve stimulation-induced renin secretion and renal vasoconstriction without affecting the norepinephrine release. Effects of ANP on other vasoconstrictive and antinatriuretic stimuli such as angiotensin II and endothelin are also demonstrated. Renal actions of NKH477 had been unknown, but we revealed that NKH477 elevates renal cAMP level and causes vasodilation and natriuresis. NKH477 also suppresses the nerve stimulation-induced renal vasoconstriction, and thereby blunts the antinatriuresis. The renal actions of these drugs clarified in our study may contribute to their curative effects on congestive heart failure.

Chronic mild or moderate stress elicits an adaptive change in central nervous systems that function to maintain homeostasis. The principal components of stress response are the extrahypothalamic corticotropin-releasing hormone (CRH) and the locus coeruleus (LC)-norepinephrine (NE) systems. CRH is known to produce various stress-, anxiety- and arousal-associated behaviors in animals. Moreover, CRH causes an increase in the firing rate and activity of tyrosine hydroxylase in the LC, and NE release in LC projection areas. It is thought that chronic inescapable and unpredictable stress can result in a sustained dysregulation of both CRH neuronal activity and LC-NE systems. One may hypothesize that the NE-CRH interaction occurs in the terminal projection of forebrain NE systems, the hypothalamic paraventricular nucleus (PVN), the bed nucleus of the stria terminalis (BNST) and the central nucleus of the amygdala (CeA) where NE stimulates CRH release. Such CRH-NE-CRH feed-forward systems elicit progressive augmentation of stress responsivity with repeated exposure. The beta-adrenergic receptor down-regulation is induced by acute and chronic exposure to moderate and predictable stress, implying an adaptation to stress. However, chronic unpredictable (variable) stress (CVS), a model for depression, up-regulated the beta-AR. In our laboratory, we found that concurrent treatment with the selective serotonin reuptake inhibitor (SSRI) citalopram caused beta-R down-regulation in the frontal cortex of rats treated with CVS for 14 days. As previously reported by the authors, an increase in 5-HT availability plays a role in preserving beta-R down-regulation by NE potentiating agents. In depressed patients, hyperactivation of the CRH-NE systems caused by the CRH-NE feed-forward system is thought to be involved in generating anxiety, sympathetic activation and hyperarousal. Moreover, a decrease in the 5-HT turnover in depressed patients has been reported. Accordingly, it is proposed that an increase in 5-HT availability by SSRI might contribute to normalize beta-R down-regulation as an adaptive regulatory mechanism against excessive CRH-NE neurotransmission under a "stressful" situation.

Isatin (indole-2,3-dione) has been found in mammalian tissues as one of major components of tribulin, a postulated endogenous marker of stress and anxiety. I previously identified isatin as an endogenous inhibitor of monoamine oxidase (MAO) in the human urine and the brain of stroke-prone spontaneously hypertensive rats (SHRSP) using GC-MS. A single dose of isatin significantly increased norepinephrine (NE) and 5-hydroxytryptamine (5-HT) concentrations measured 2 h later in the various brain regions of normotensive Wistar Kyoto rats (WKY). Striatal acetylcholine (ACh) and dopamine (DA) levels significantly increased 2 h after the administration of isatin. Perfused through a microdialysis probe, isatin also produced a significant and concentration-dependent increase in the ACh and DA concentration in the perfusate from the rat striatum. In the patients with Parkinson's disease, urinary isatin concentrations tended to increase according to the severity of disease, as classified by the Hoehn and Yahr criteria. Isatin significantly increased striatal DA levels in a rat model of Parkinson's disease. Isatin may play a role in the regulation of the brain levels of ACh and DA. Furthermore, isatin has a wide spectrum of biological properties: (a) a marker of stress and anxiety, (b) an inhibitor of a number of enzymes, (c) an anti-seizure agent, (d) an inhibitor of benzodiazepin receptors and ANP binding to its receptors.

Nitriles are widely used in industry as plastics, solvents, and synthetic intermediates. It has been shown that the thermal degradation of acrylonitrile-based plastics leads to the emission of a great variety of nitriles. Exposure of humans and experimental animals to some nitriles has been shown to lead to disorders of the central nervous, hepatic, cardiovascular, renal, and gastrointestinal systems. Iminodipropionitrile has long been known to induce in experimental animals behavioral syndromes that other nitriles have not been reported to induce. Recently, we have found that a single administration of allylnitrile, an analog of acrylonitrile, induces in rodents behavioral abnormalities including head twitching, head weaving, random circling, increased locomotor activity, backward pedaling, pivoting, and somersaulting. The induced abnormalities were persistent. Crotononitrile and 2-pentenenitrile also are able to produce behavioral abnormalities. Thus, the nitriles appear as a new class of neurotoxic compounds with potential relevance to the human health. The mechanism by which allylnitrile induces and maintains the behavioral abnormalities is summarised below. 1. Allylnitrile activates the serotonin (5-HT) system in the central nervous system, and as a consequence activation of 5-HT-2 receptors due to increased 5-HT may lead to induction of head twitching. 2. Although the data available indicate that the dopamine (DA) system may be involved in allylnitrile-induced behavioral abnormalities, it remains unknown how the DA system relates to the abnormalities. 3. Allylnitrile decreases the noradrenaline level in the central nervous system, which is thought to be secondary to the 5-HT system activation mentioned above. The allylnitrile-induced head twitching, however, may occur in consequence to both enhanced beta-adrenoceptor stimulation and to the removal of tonic inhibitory control by alpha-2-adrenoceptors. 4. The neuropathological data indicate an important role of the medial habenular and raphe nuclei in allylnitrile-induced behavioral abnormalities. Onset of the behavioral abnormalities appears to be associated with the impairment in the medial habenulo-raphe relay owing to activation of apoptotic cascade in neurons. 5. On the basis of the findings with iminodipropionitrile and crotononitrile, allylnitrile might produce pathological changes in the vestibular sensory hair cells. Further studies are needed to explore the mechanism underlying the allylnitrile-induced syndromes.

The purinergic modulation of the release of norepinephrine (NE) from sympathetic nerves in the rabbit ear artery was investigated. Methoxamine, an alpha 1-adrenoceptor agonist, enhanced the NE-release by electrical stimulation (ES) and released large amounts of adenyl purines (ATP, ADP, AMP and adenosine) from the endothelium. Both actions of methoxamine were blocked by prazosin. In addition, the enhancement of the NE-release by methoxamine was abolished by 8-sulfophenyl theophylline (8SPT), a P1-Purinoceptor antagonist. These findings indicated that the endogenous purines and purinoceptors participate in the facilitation of NE-release by alpha 1-adrenoceptor stimulation. P1-Purinoceptor agonists, such as adenosine and 2-chloroadenosine, and P2-purinoceptor agonists, such as ATP and beta,gamma-methylene ATP (beta gamma-mATP), enhanced the ES-evoked NE-release. This enhancement was antagonized not only by the P1-purinoceptor antagonist, 8SPT, but also by the P2-purinoceptor desensitizing agent, alpha,beta-methylene ATP. A phosphodiesterase inhibitor, Ro20-1724 potentiates the enhancement of NE-release by beta gamma-mATP. On the other hand, an adenylate cyclase inhibitor, SQ22536, inhibited the enhancement of NE-release by beta gamma-mATP. These findings suggested that prejunctional facilitatory purinoceptors exist on the adrenergic nerves of the rabbit ear artery. This receptor may be coupled to adenylate cyclase and is different from well-known P1 and P2 purinoceptors. In the rabbit ear artery, adrenergic neurotransmission may be regulated by endogenous ATP and its metabolites via prejunctional facilitatory purinoceptors, which were initiated by alpha 1-adrenoceptor stimulation; i.e. transsynaptic regulation of neurotransmission.

Research on the interaction of ethanol and stress with experimental animals are briefly reviewed. There might be the two aspects of the interaction of stress and ethanol, i.e., how stress affects ethanol ingestion and response to ethanol, and how ethanol modifies stress response. In general, stress increases ingestion of ethanol in animals exposed to various stresses including electric shock, immobilization and psychological or emotional stresses, wherein the psychological or emotional factors were predominantly involved. However, in most cases, ethanol ingestion is increased after release from stress not during exposure to stress. A variety of stressful stimuli caused marked increases in the neurotransmitter release in many brain regions. Immobilization stress increased noradrenaline release in the extended brain regions in rats. These increases were significantly attenuated by pretreatment with ethanol in the rat amygdala and locus coeruleus, but not in the hypothalamus, although ethanol by itself increased noradrenaline release in the hypothalamus. Further, psychological stress, wherein the rats were given no electrical shock, but exposed to the emotional responses such as struggling, vocalization, jumping and defecation shown by the other electrically-shocked rats, increased noradrenaline release preferentially in the hypothalamus, amygdala and locus coeruleus. Among the former two regions, stress-induced increases in noradrenaline release were significantly attenuated by ethanol in the amygdala, but not in the hypothalamus. Together with the finding that increases, in noradrenaline release are closely related to the provocation of anxiety and/or fear, ethanol, in part, reduced tension, as mentioned in the tension reduction hypothesis, by attenuating stress-induced increases in noradrenaline release in the amygdala and locus coeruleus. Moreover, ethanol, administered i.p. and directly through the microdialysis probe, increased dopamine release in the nucleus accumbens assessed by in vivo microdialysis, similarly as addictive drugs such as amphetamine did. This might be, in part, neurochemical basis for motivation of repeated drinking of ethanol.

To analyze the effects of antidepressants on the GABAA receptor, we investigated how the chronic administration of antidepressants (10 mg/kg twice a day for three or seven days, ip) influenced the power-spectral changes induced by pentylenetetrazol (PTZ; a GABA antagonist; 27.5 mg/kg) or beta-carboline-3-carboxylic-acid-methylester (beta-CCM; an inverse agonist; 1 mg/kg) on rat hippocampal EEGs. PTZ and beta-CCM are known to inhibit the chloride ionophore and benzodiazepine receptor (GABAA receptor complex), respectively. After the ip injection of both compounds, the EEG power under 12 Hz increased to about five times that before injection. Between the rats that did not receive any antidepressants and all those injected with the drugs for 3 days or treated with desipramine (DMI) for 7 days, there were no apparent changes in the effect of PTZ or beta-CCM. However, in the rats treated with imipramine, fluoxetine or trazodone for 7 days, the increase in power after the injection of PTZ or beta-CCM was apparently suppressed. In these rats, the power values were less than three times those before the dosing of PTZ or beta-CCM. DMI is known to inhibit the re-uptake of norepinephrine (NE), while the other three antidepressants inhibit that of serotonin (5-HT). Trazodone is also reported to block the 5-HT2 sites. These observations might indicate that the chronic administration of antidepressants prompted the function of the GABAA receptor complex. Moreover, it is also suggested that, to that action, the effect of antidepressants on the 5-HT system or interaction between the 5-HT system and GABA receptors might play some role.

The release of norepinephrine (NE) in the ventral hippocampus was studied in rats with microdialysis method. The basal release of NE with perfusion of normal artificial cerebrospinal fluid (ACSF) was 1.58 +/- 0.37 x 20 microliters-1 sample. The NE concentration increased significantly with perfusion of high potassium (60 mM) ACSF indicating that depolarization-induced release was up to 5 times higher than the basic level. Ketamine (20 mg.kg-1 and 80 mg.kg-1 im) significantly inhibited the depolarization-induced increase of NE, but did not affect the basal release. Neither 5 mg.kg-1 im of ketamine nor MK-801 had any effect on the basic or the depolarization-induced release. These results suggest that the inhibitory effect of ketamine on the depolarization-induced NE release was not due to the NMDA channel blocking properties of ketamine.

Recent technical advances have made it possible to investigate quantitatively the ionic events underlying pacemaker activity in the sinoatrial node. Various time-dependent currents through ion channels such as the delayed rectifier K current, two types of Ca currents and the hyperpolarization-activated current have been found to play an important role in the generation of the pacemaker activity of sinoatrial node cells. Time-independent background currents, transporter-mediated current and pump current also contribute to pacemaker activity. In this article, the physiological significance of these currents for the pacemaker depolarization and their modulation by autonomic nerves and humoral factors are discussed.

Although many studies have examined the metabolism of catecholamines and cardiovascular responsiveness to norepinephrine in essential and various experimental hypertension, the role of sympathetic nervous system in the pathogenesis of hypertension has not been elucidated. In this study, therefore,the role of sympathetic nerve activity related to platelet alpha 2-adrenoceptor was investigated to clarify the mechanism in which sympathetic nervous system augments the blood pressure elevation in patients with essential hypertension (EHT). Tritiated yohimbine binding was used to estimate platelet membrane alpha 2-adrenoceptor characteristics in 27 hospitalized patients with mild to moderate EHT and 27 normotensive subjects (NT) receiving a regular diet containing 120mEq/day of sodium and 75mEq/day of potassium. In this study, mean arterial pressure (MAP) and plasma norepinephrine concentration (pNE) was significantly higher in EHT than those in NT. Total binding sites (Bmax) and dissociation constant (Kd) for 3H-yoshimbine in EHT was also significantly higher than those in NT. There was a significant positive correlation between Bmax and age in NT, but not in EHT. A significant positive correlation was observed between the pressor response to infused norepinephrine (NE-R:increments in MAP induced by i.v. infused 0.2 micrograms/kg/min of NE) and Bmax both in NT and EHT. On the other hand, no significant correlation was found between NE-R and Kd in NT and EHT. In addition, Bmax was correlated inversely with PNE in both NT and EHT. These findings suggest that down-regulation mechanism exists in platelet alpha 2-adrenoceptor number responded to PNE levels. Moreover, the increased density of alpha-adrenoceptor might have something to do with the augmented NE-R in EHT, indicating an important pathophysiological role of this receptor in the hypertensive mechanisms in EHT.

To characterize regional cardiac sympathetic dysfunction due to myocardial ischemia, we examined 123I-metaiodobenzylguanidine (MIBG) myocardial distribution of initial 15-min and 4-hr delayed SPECT images in 14 patients with recent myocardial infarction (MI), 25 patients with vasospastic angina which was angiographically proven with elgonovine maleate (Gp VSAP) and 16 patients with chest pain syndrome and normal CAG findings (GpCP). In those with MI, the study was serially done at 2 weeks after (Gp MI-1) and at 3 months after the onset of MI (Gp MI-2). We estimated regional tracer uptake in 20 segments of tomographic images by using a 4-point scoring system (0 = normal, 1 = mild, 2 = moderate, 3 = severe reduction) and calculated the total defect score (IDS). In all patients with MI, the area of reduced MIBG uptake was more extensive than the 201Tl perfusion defect in the acute stage (Gp MI-1) indicating the presence of viable but denervated myocardial tissue. Also, the MIBG defect was persistently observed from initial (TDS: 24 +/- 13) to delayed imaging (TDS: 26 +/- 12). However, in the chronic stage (Gp MI-2), the initial MIBG uptake improved (TDS: 18 +/- 9) but the delayed uptake remained almost the same (TDS: 22 +/- 10) indicating high washout of MIBG from the ischemic myocardium. Fourteen in Gp VSAP and 14 in Gp CP showed the regional MIBG defect in the delayed image more extensively than in the initial image indicating high washout of MIBG in the involved myocardial regions. These results suggest that neuronal uptake of MIBG is impaired in the acute stage of MI although neuronal retention of MIBG is predominantly impaired in the chronic stage of MI or in Gps VSAP and CP.

The effect of fluvoxamine (FLU) on the amine dynamics in serotonergic, noradrenergic or dopaminergic nervous systems in the rat cerebral limbic system was investigated, with reference to the pharmacological characteristics of FLU. Following single oral administration of 30 and/or 60 mg/kg FLU, significant decreases in the 5-hydroxyindole-3-acetic acid (5-HIAA)/serotonin (5-HT) ratios in the amygdala and hippocampus and the 4-hydroxy-3-methoxyphenylglycol (MHPG)/norepinephrine (NE) ratio in the amygdala were produced. FLU at 15 mg/kg, p.o. also caused a significant increase in MHPG/NE ratio in the hippocampus. On the other hand, imipramine (IMI) at 30 mg/kg, p.o. induced significant decreases in 5-HIAA/5-HT ratio in the hippocampus, MHPG/NE ratios in the amygdala and hippocampus, and 3,4-dihydroxyphenylacetic acid (DOPAC)/dopamine (DA) ratios in the amygdala, hippocampus and septum. The 5-HIAA/5-HT ratios in the amygdala and hippocampus and the MHPG/NE ratio in the septum were significantly decreased after repeated oral administration of 30 mg/kg FLU twice daily for 14 days, but the MHPG/NE ratio in the amygdala was increased. In the septum, DOPAC/DA ratio was significantly decreased following repeated administration of IMI at 30 mg/kg, p.o. These findings suggest that FLU inhibits 5-HT turnover in the amygdala and hippocampus as a result of the interference with the neuronal re-uptake mechanism for 5-HT. Also, FLU has an effect on NE turnover in the cerebral limbic system, and the effect may appear in connection with a change in the interaction of nervous systems.

Supplement of the deficient neurotransmitters is one of the most effective therapies for neurodegenerative disorders. For the treatment of Parkinson's disease, L-DOPA therapy has been applied to replace dopamine, and droxidopa (L-threo-3,4-dihydroxyphenylserine) therapy to supply noradrenaline (NA). Droxidopa, an artificial amino acid, is decarboxylated by aromatic L-amino acid decarboxylase (AADC) into NA. By application for Parkinson's disease, it alleviated neurological symptoms such as freezing phenomenon, which are refractory to L-DOPA. However, as a precursor of a monoamine, droxidopa was found to be not so effective as L-DOPA; and the clinical efficiency of droxidopa is variable among patients. The metabolic pathway of droxidopa in the brain was examined using human materials. The intraventricular fluid of patients treated with droxidopa, and of control was analyzed by high-performance liquid chromatography with multi-eletrochemical detection (Neurochem). In the intraventricular fluid of the patients treated, free NA concentration increased to be 5.67 +/- 3.40 nM from non-detectable level in the control patients. The patients with higher free NA levels clinically responded better to droxidopa. However, free NA levels varied among patients; and the mechanism of the individual variance should be clarified. In the intraventricular fluid, in addition to NA, a large amount of a metabolite of droxidopa by catechol-O-methyltransferase (COMT), 3-O-methoxy-droxidopa (3OMD), was detected, followed by the metabolites by DOPS-aldolase (DOPS-ALD), protocatechualdehyde and protocatechuic acid. It indicates that considerable parts of administered droxidopa are catabolized by COMT and DOPS-ALD, but not by AADC.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was aimed to make a new stable model of chronic hypertension by administration of a nitric oxide synthase inhibitor. L-Nw-nitroarginine methylester (NAME), and using this model, to investigate the roles of nitric oxide for the cardiovascular regulation. Male Wistar rats were implanted of osmotic pumps filled with saline (control group: n = 8), 0.2M NAME (low NAME group: n = 13) or 1M NAME (high NAME group: n = 12) intraperitoneally. After 4-week observation of blood pressure (BP) and heart rate (HR), blood concentrations of cathecholamine, active renin, L-arginine and L-Nw-nitroarginine were measured and histological changes in aorta and heart were examined. Age-matched SHRSP (n = 9) served as positive controls. BP elevated in the low NAME and high NAME group (113.9 +/- 3.1 to 144.0 +/- 4.4 mmHg, and 114.1 +/- 7.3 to 181.4 +/- 9.0 mmHg, respectively; mean +/- S.E.), while BP remained constant in the control group and SHRSP group (116.8 +/- 5.5 to 120.6 +/- 1.9 mmHg, 200.3 +/- 5.1 to 213.8 +/- 7.4 mmHg, respectively). HR in the low NAME and high NAME group rapidly decreased (not equal to 410 to not equal to 340 bpm) and then slowly returned to the control level. HR in the control group and SHRSP group remained constant (not equal to 420 and not equal to 450 bpm, respectively). Noradrenaline increased significantly in the high NAME group (0.21 +/- 0.03 ng/ml), and there were no significant changes in the control, low NAME and SHR group (0.13 +/- 0.02, 0.14 +/- 0.02, 0.15 +/- 0.03 ng/ml, respectively). Adrenaline, dopamine and active renin concentrations did not differ among 4 groups. Aortic wall/lumen area ratio in the high NAME group was similar to that in SHRSP group, in spite of its lower BP and shorter duration of hypertension compared with SHRSP. Left ventricular wall of the high NAME group was significantly thicker than that of SHRSP group. These findings suggest that, in addition to endothelium-derived NO, NO produced in the brain and peripheral neurons may function to regulate cardiovascular system by inhibiting noradrenaline release from sympathetic nerves or by inhibiting cardiac and vascular cell proliferation.