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During postnatal life, leptin specifies neuronal inputs to the paraventricular nucleus of the hypothalamus (PVH) and activates agouti-related peptide (AgRP) neurons in the arcuate nucleus of the hypothalamus. Activity-dependent developmental mechanisms impact refinement of sensory circuits, but whether leptin-mediated postnatal neuronal activity specifies hypothalamic neural projections is largely unexplored. Here, we used chemogenetics to manipulate the activity of AgRP neurons during a discrete postnatal critical period and evaluated the development of AgRP inputs to the PVH and descending efferent outflow to the dorsal vagal complex (DVC). In leptin-deficient mice, targeting of AgRP neuronal outgrowth to PVH oxytocin neurons was reduced, and despite the lack of leptin receptors found on oxytocin neurons in the PVH, oxytocin-containing connections to the DVC were also impaired. Activation of AgRP neurons during early postnatal life not only normalized AgRP inputs to the PVH but also oxytocin outputs to the DVC in leptin-deficient mice. Blocking AgRP neuron activity during the same postnatal period reduced the density of AgRP inputs to the PVH of wild type mice, as well as the density of oxytocin-containing DVC fibers, and these innervation deficits were associated with dysregulated autonomic function. These findings suggest that leptin-mediated AgRP neuronal activity is required for the development of PVH connectivity and represents a unique activity-dependent mechanism for specification of neural pathways involved in the hypothalamic integration of autonomic responses. [ABSTRACT FROM AUTHOR]

Norepinephrine (NE) modulates synaptic transmission and long-term plasticity through distinct subtype adrenergic receptor (AR)-mediated-intracellular signaling cascades. However, the role of NE modulates glutamatergic long-term potentiation (LTP) in the hypothalamic paraventricular nucleus (PVN) magnocellular neuroendocrine cells (MNCs) is unclear. We here investigate the effect of NE on high frequency stimulation (HFS)-induced glutamatergic LTP in rat hypothalamic PVN MNCs in vitro, by whole-cell patch-clamp recording, biocytin staining and pharmacological methods. Delivery of HFS induced glutamatergic LTP with a decrease in N2/N1 ratio in the PVN MNCs, which was enhanced by application of NE (100 nM). HFS-induced LTP was abolished by the blockade of N-methyl-D-aspartate receptors (NMDAR) with D-APV, but it was rescued by the application of NE. NE failed to rescue HFS-induced LTP of MNCs in the presence of a selective β1-AR antagonist, CGP 20712. However, application of β1-AR agonist, dobutamine HCl rescued HFS-induced LTP of MNCs in the absence of NMDAR activity. In the absence of NMDAR activity, NE failed to rescue HFS-induced MNC LTP when protein kinase A (PKA) was inhibited by extracellular applying KT5720 or intracellular administration of PKI. These results indicate that NE activates β1-AR and triggers HFS to induce a novel glutamatergic LTP of hypothalamic PVN NMCs via the postsynaptic PKA signaling pathway in vitro in rats. [ABSTRACT FROM AUTHOR]

Objective To probe the spatial distribution of respiratory-related nuclei throughout the whole brain, and to investigate the circuit and projection links between the paraventricular hypothalamic nucleus (PVN) and the preBötzinger complex (preBötC) in mice. Methods Using a retrograde tracing strategy from peripheral to central, pseudorabies viruses (PRV) were microinjected into the diaphragm of mice to retrogradely label the upstream inputs brain regions from spinal respiratory phrenic motor neurons. The anterograde non-transsynaptic tracing viruses (AAV2/9-EGFP) were microinjected into the PVN to label the downstream brain region of the PVN; And using the Cre/loxP gene expression strategy, Dio-EGFP and Retro-Cre viruses were injected in the PVN and preBötC, respectively, to validate the PVN-preBötC circuit and the projection relationship between the two. Results The results of PRV-mediated retrograde tracing showed that PRV-EGFP-positive neurons were distributed in several brain regions such as PVN, preBötC, nucleus tractus solitarii (NTS), locus coeruleus (LC) and periaqueductal grey (PAG). Except for the medulla oblongata region, the PVN brain region had the highest percentage of PRV-EGFP-positive neurons (P < 0.000 1). After AAV2/9-EGFP viruses were injected in the PVN, green neurofibrils were observed in the preBötC brain region after viral infection; Dio-EGFP and Retro-Cre viruses were injected in the PVN and preBötC, respectively, and green neuronal cells were seen in the brain region of the PVN after viral infection. Conclusion PVN is an important upstream input nucleus of spinal respiratory phrenic motor neurons, and has the potential to regulate respiration through direct projections from PVN-preBötC circuit.

Purpose of Review: Oxytocin plays many diverse roles in physiological and behavioral processes, including social activity, parental nurturing, stress responses, and sexual function. In this narrative review, we provide an update on the most noteworthy recent findings in this fascinating field. Recent Findings: The development of techniques such as serial two-photon tomography and fiber photometry have provided a window into oxytocin neuroanatomy and real-time neuronal activity during social interactions. fMRI and complementary mapping techniques offer new insights into oxytocin's influence on brain activity and connectivity. Indeed, oxytocin has recently been found to influence the acquisition of maternal care behaviors and to mediate the influence of social touch on brain development and social interaction. Additionally, oxytocin plays a crucial role in male sexual function, affecting erectile activity and ejaculation, while its role in females remains controversial. Recent studies also highlight oxytocin's interaction with other neuropeptides, such as melanin-concentrating hormone, serotonin, and arginine vasopressin, influencing social and affective behaviors. Finally, an update is provided on the status of clinical trials involving oxytocin as a therapeutic intervention. Summary: The exploration of oxytocin's complexities and its interplay with other neuropeptides holds promise for targeted treatment in various health and disease contexts. Overall, these findings contribute to the discovery of new and specific pathways to allow therapeutic targeting of oxytocin to treat disorders. [ABSTRACT FROM AUTHOR]

Understanding of central nervous system mechanisms underlying age-related infertility remains limited. Fibril α-synuclein, distinct from its monomeric form, is implicated in age-related diseases. Notably, fibril α-synuclein spreads among neurons, similar to prions, from damaged old neurons in cortex and hippocampus to healthy neurons. However, less is known whether α-synuclein propagates into oxytocin neurons, which play crucial roles in reproduction. We compared α-synuclein expression in the oxytocin neurons in suprachiasmatic nucleus (SCN), supraoptic nucleus (SON), paraventricular hypothalamic nucleus (PVN), and posterior pituitary (PP) gland of healthy heifers and aged cows to determine its role in age-related infertility. We analyzed mRNA and protein expression, along with Congo red histochemistry and fluorescent immunohistochemistry for oxytocin and α-synuclein, followed by confocal microscopy with Congo red staining. Both mRNA and protein expressions of α-synuclein were confirmed in the bovine cortex, hippocampus, SCN, SON, PVN, and PP tissues. Significant differences in α-synuclein mRNA expressions were observed in the cortex and hippocampus between young heifers and old cows. Western blots showed five bands of α-synuclein, probably reflecting monomers, dimers, and oligomers, in the cortex, hippocampus, SCN, SON, PVN, and PP tissues, and there were significant differences in some bands between the young heifers and old cows. Bright-field and polarized light microscopy did not detect obvious amyloid deposition in the aged hypothalami; however, higher-sensitive confocal microscopy unveiled strong positive signals for Congo red and α-synuclein in oxytocin neurons in the aged hypothalami. α-synuclein was expressed in oxytocin neurons, and some differences were observed between young and old hypothalami. [ABSTRACT FROM AUTHOR]

Understanding of central nervous system mechanisms underlying age-related infertility remains limited. Fibril α-synuclein, distinct from its monomeric form, is implicated in age-related diseases. Notably, fibril α-synuclein spreads among neurons, similar to prions, from damaged old neurons in cortex and hippocampus to healthy neurons. However, less is known whether α-synuclein propagates into oxytocin neurons, which play crucial roles in reproduction. We compared α-synuclein expression in the oxytocin neurons in suprachiasmatic nucleus (SCN), supraoptic nucleus (SON), paraventricular hypothalamic nucleus (PVN), and posterior pituitary (PP) gland of healthy heifers and aged cows to determine its role in age-related infertility. We analyzed mRNA and protein expression, along with Congo red histochemistry and fluorescent immunohistochemistry for oxytocin and α-synuclein, followed by confocal microscopy with Congo red staining. Both mRNA and protein expressions of α-synuclein were confirmed in the bovine cortex, hippocampus, SCN, SON, PVN, and PP tissues. Significant differences in α-synuclein mRNA expressions were observed in the cortex and hippocampus between young heifers and old cows. Western blots showed five bands of α-synuclein, probably reflecting monomers, dimers, and oligomers, in the cortex, hippocampus, SCN, SON, PVN, and PP tissues, and there were significant differences in some bands between the young heifers and old cows. Bright-field and polarized light microscopy did not detect obvious amyloid deposition in the aged hypothalami; however, higher-sensitive confocal microscopy unveiled strong positive signals for Congo red and α-synuclein in oxytocin neurons in the aged hypothalami. α-synuclein was expressed in oxytocin neurons, and some differences were observed between young and old hypothalami.

Objectives: The up-regulation of proinflammatory cytokines in the hypothalamic paraventricular nucleus (PVN) is well demonstrated to be involved in the development of neurogenic hypertension, including stress-induced hypertension (SIH). IL-17A has been found to be increased in the PVN of several hypertensive animal models and has been shown to play a key role in the development of hypertension. Although IL-36γ was found to be expressed in spinal neurons, its role in hypertension remains elusive. Here, we investigated the co-expression of IL-17 receptor A (IL-17RA) and IL-36γ in the PVN cells of SIH rats. Methods: The electric foot shock combined with buzzer noise stressors were used to make hypertensive rat model. The immunochemical staining or immunofluorescence staining was used to reveal cells as requested. The Western blot was used to detect the related protein levels. Results and Conclusion: In the PVN of the SIH rats, the number of CD3+CD4+ T cells was significantly increased by the immunochemical staining. Additionally, the protein levels of RORγt and IL-17A were significantly upregulated by Western blot, confirming the infiltration of CD4+ T cells and differentiation into Th17 cells in the PVN of SIH rats. Immunofluorescence staining revealed abundant expression of IL-17RA in PVN neurons, with relatively less expression in astrocytes or microglia. Furthermore, IL-36γ positive cells and protein expression of IL-36R were significantly increased. Notably, this study demonstrates for the first time that most IL-36γ cells were strongly colocalized with IL-17RA positive cells in the PVN of SIH rats, and the colocalized cells were significantly higher in SIH rats. This suggests that IL-17A secreted by infiltrated Th17 cells may stimulate PVN neurons to produce IL-36γ via IL-17RA, indicating that the combination of IL-17 and IL-36γ might produce strong pro-inflammatory effects in the PVN of SIH rats. [ABSTRACT FROM AUTHOR]

Objective(s): High levels of resistin are associated with metabolic diseases and their complications, including hypertension. The paraventricular nucleus (PVN) is also involved in metabolic disorders and cardiovascular diseases, such as hypertension. Therefore, this study aimed to study cardiovascular (CV) responses evoked by the injection of resistin into the lateral ventricle (LV) and PVN and determine the mechanism of these responses in the rostral ventrolateral medulla (RVLM).Materials and Methods: Arterial pressure (AP) and heart rate (HR) were evaluated in urethane-anesthetized male rats (1.4 g/kg intraperitoneally) before and after all injections. This study was carried out in two stages. Resistin was injected into LV at the first stage, and AP and HR were evaluated. After that, the paraventricular, supraoptic, and dorsomedial nuclei of the hypothalamus were chosen to evaluate the gene expression of c-Fos. Afterward, resistin was injected into PVN, and cardiovascular responses were monitored. Then to detect possible neural mechanisms of resistin action, agonists or antagonists of glutamatergic, GABAergic, cholinergic, and aminergic transmissions were injected into RVLM. Results: Resistin injection into LV or PVN could increase AP and HR compared to the control group and before injection. Resistin injection into LV also increases the activity of RVLM, paraventricular, supraoptic, and dorsomedial areas. Moreover, the CV reflex created by the administration of resistin in PVN is probably mediated by glutamatergic transmission within RVLM. Conclusion: It can be concluded that hypothalamic nuclei, including paraventricular, are important central areas for resistin actions, and glutamatergic transmission in RVLM may be one of the therapeutic targets for high AP in obese people or with metabolic syndrome.

Objectives: Yokukansan (YKS) is a traditional Japanese Kampo medicine approved by the Ministry of Health, Labour and Welfare of Japan. Recently, in addition to its indications as a drug treatment, YKS has been shown to have ameliorative effects on various psychological and behavioral responses such as anxiety, aggression, and stress responses. Stress exposure activates not only the hypothalamic-pituitary-adrenal axis but also the sympathetic nervous system. Sympathetic activation in brain regions such as the paraventricular hypothalamic nucleus (PVN) stimulates elevation of plasma catecholamine (noradrenaline and adrenaline) levels. We previously reported that various stress-related neuropeptides and several kinds of stressors, such as restraint stress (RS), increase plasma catecholamine and that brain prostanoids and their synthases mediate these responses in rats. In the present study, to determine if YKS treatment can affect stress-induced sympathetic activation, we examined the effects of YKS treatment on the RSinduced elevation of plasma catecholamine levels and related prostanoid production in the PVN of rats. Methods: YKS (1000 mg/10 mL/kg, p.o.) or vehicle was administered to rats daily for 14 days, and all rats were exposed to RS for 60 min on day 14. Before and during stress exposure on day 14, blood samples and PVN dialysates were collected and analyzed by high-performance liquid chromatography and liquid chromatography-ion trap tandem mass spectrometry, respectively. Results: Our results showed that repeated administration of YKS suppressed the RS-induced increase in plasma adrenaline but not noradrenaline. Furthermore, YKS administration also suppressed the RS-induced elevation of both prostaglandin E2 and thromboxane B2 levels in the PVN. In addition, we found that repeated administration of YKS suppressed the RS-induced increase in serotonin, gamma-aminobutyric acid, and acetylcholine in the PVN. Conclusion: Our results suggest that YKS can ameliorate stress-induced sympathetic activation via inhibition of stress responses in the brain. [ABSTRACT FROM AUTHOR]

The locus coeruleus (LC), enriched in vesicular glutamate transporter 2 (VGlut2) neurons, is a potential homeostasis‐regulating hub. However, the identity of melanocortin‐4 receptor (MC4R) neurons in the paraventricular nucleus (PVN) of the hypothalamus, PVNVGlut2::MC4R and LCVGlut2::MC4R regulation of body weight, and axonal projections of LCVGlut2 neurons remain unclear. Conditional knockout of MC4R in chimeric mice was used to confirm the effects of VGlut2. Interscapular brown adipose tissue was injected with pseudorabies virus to study the central nervous system projections. We mapped the LCVGlut2 circuitry. Based on the Cre–LoxP recombination system, specific knockdown of MC4R in VGlut2 neurons resulted in weight gain in chimeric mice. Adeno‐associated virus‐mediated knockdown of MC4R expression in the PVN and LC had potential superimposed effects on weight gain, demonstrating the importance of VGlut2 neurons. Unlike these wide‐ranging efferent projections, the PVN, hypothalamic arcuate nucleus, supraoptic nucleus of the lateral olfactory tegmental nuclei, and nucleus tractus solitarius send excitatory projections to LCVGlut2 neurons. The PVN → LC glutamatergic MC4R long‐term neural circuit positively affected weight management and could help treat obesity. [ABSTRACT FROM AUTHOR]

Background: Early non-motor features including anxiety, depression and altered social cognition are present in Huntington's disease (HD). The underlying neurobiological mechanisms are not known. Oxytocin (OXT) is involved in the regulation of emotion, social cognition and metabolism, and our previous work showed that the OXT system is affected early in HD. The aim of the study was to investigate the potential causal relationship between the selective expression of mutant huntingtin (mHTT) in OXT neurons and the development of non-motor features and neuropathology. Methods: To express mHTT only in OXT neurons, we used a novel flex-switch adeno-associated viral vector design to selectively express either mHTT or wild-type HTT in the paraventricular nucleus of the hypothalamus using OXT-Cre-recombinase mice. We also performed a mirror experiment to selectively delete mHTT in OXT neurons using the BACHD mouse model. Mice underwent a battery of behavioural tests to assess psychiatric and social behaviours 3 months post-injection or at 2 months of age, respectively. Post-mortem analyses were performed to assess the effects on the OXT system. Results: Our results show that selective expression of mHTT in OXT neurons was associated with the formation of mHTT inclusions and a 26% reduction of OXTimmunopositive neurons as well as increased anxiety-like behaviours compared with uninjected mice. However, selective deletion of mHTT from OXT neurons alone was not sufficient to alter the metabolic and psychiatric phenotype of the BACHD mice at this early time point. Conclusions: Our results indicate that mHTT expression can exert cell-autonomous toxic effects on OXT neurons without affecting the non-motor phenotype at early time points in mice. [ABSTRACT FROM AUTHOR]

The aim of our study was to compare the effects of a gold salt (sodium tetrachloroaurate) and gold nanoparticles colloidal solution on the morphofunctional state of the hypothalamus and adrenal glands of 6-month-old male rats with obesity, which was induced using a diet-induced model of metabolic disorders. The rats, modeled for obesity, were divided into three groups that received a NaCl solution, gold salt solution and colloidal solution of gold nanoparticles for 10 days. Rats of the control group received a standard diet. After the end of the experiment, the hypothalamic nuclei and adrenal glands, prepared according to the appropriate histological methods, were collected from the animals. In the paraventricular nucleus of the hypothalamus, a small-cell area of neurons was examined. In the adrenal glands, cells of three zones of the cortex were examined: glomerular, fascicular, and reticular. The results of the study showed that obesity led to the increase of functional activity in the nuclei of neurons in the small-cell region of the paraventricular nucleus of the rat hypothalamus. Functional activity increased maximally in the cells of the glomerular zone of the adrenal cortex, moderately increased in the fascicular zone, and no significant changes were recorded in the reticular zone. It was shown that the gold salt caused a decrease in the functional activity of neurons of the paraventricular nucleus of the hypothalamus in obese rats. In the glomerular zone of the adrenal cortex, the functional activity of cells significantly decreased; in the fascicular zone, the parameters of cell nuclei decreased to a greater extent; in the reticular zone, there were almost no changes. The introduction of gold nanoparticles colloidal solution caused the intensification of functional activity of the paraventricular hypothalamic nucleus cells in obese rats. In the glomerular zone of the adrenal cortex, cell parameters decreased; in the fascicular zone, cytoplasmic parameters decreased, but nuclear parameters did not change; in the reticular zone, measured values of nuclei increased and cytoplasmic parameters remained unchanged. In general, the administration of gold nanoparticles colloidal solution produced more pronounced effects than gold salt solution on cells of the paraventricular nucleus of the hypothalamus and the adrenal cortex in obese rats. [ABSTRACT FROM AUTHOR]

Organotins such as tributyltin chloride (TBT), are highly diffused environmental pollutants, which act as metabolism disrupting chemicals, i.e. may interfere with fat tissue differentiation, as well as with neuroendocrine circuits, thus impairing the control of energetic balance. We have previously demonstrated that adult exposure to TBT altered the expression of neuropeptides in the hypothalamus. In this study, we orally administered daily a solution containing oil, or TBT (0.25, 2.5, or 25 μg/kg body weight/day) to pregnant females from gestational day 8 until birth, and to their pups from day 0 until post‐natal day 21. Our results showed that TBT exposure of female mice during gestation and of pups during lactation permanently altered the feeding efficiency of pups of both sexes and subcutaneous fat distribution in adult males. In addition, the neuropeptide Y system was affected at the level of the paraventricular nucleus, with a decrease in immunoreactivity in both sexes (significant in females for all TBT doses and in males only for intermediate TBT doses), while no effect was observed in other hypothalamic areas (arcuate, ventromedial and dorsomedial nuclei). Metabolic syndrome, as well as obesity and diabetes, which are significant health issues, are considered multifactorial diseases and may be caused by exposure to metabolic disruptors, both in adults and during perinatal life. In addition, our work indicates that TBT doses defined as the tolerably daily intake had a profound and sex‐specific long‐term effect. [ABSTRACT FROM AUTHOR]

Stressful stimuli can activate the hypothalamic-pituitary-adrenal (HPA) axis. Clinically, it has been widely reported that stressful events are often accompanied by teeth clenching and bruxism, while mastication (chewing) can promote coping with stress. Trigeminal motoneurons in the trigeminal motor nucleus supplying the chewing muscles receive direct inputs from interneurons within the peritrigeminal premotor area (Peri5). Previous studies found that the paraventricular hypothalamic nucleus (PVH) participates in trigeminal activities during stressful events. However, the neural pathway by which the stress-induced oral movements alleviate stress is largely unknown. We hypothesized that paraventricular-trigeminal circuits might be associated with the stress-induced chewing movements and anxiety levels. First, we observed the stress-coping effect of wood gnawing on stress-induced anxiety, with less anxiety-like behaviors seen in the open field test and elevated plus maze, as well as decreased corticosterone and blood glucose levels, in response to stress in mice. We then found that excitotoxic lesions of PVH reduced the effect of gnawing on stress, reflected in more anxiety-like behaviors; this emphasizes the importance of the PVH in stress responses. Anterograde, retrograde, transsynaptic, and nontranssynaptic tracing through central and peripheral injections confirmed monosynaptic projections from PVH to Peri5. We discovered that PVH receives proprioceptive sensory inputs from the jaw muscle and periodontal ligaments, as well as provides motor outputs via the mesencephalic trigeminal nucleus (Me5) and Peri5. Next, pathway-specific functional manipulation by chemogenetic inhibition was conducted to further explore the role of PVH-Peri5 monosynaptic projections. Remarkably, PVH-Peri5 inhibition decreased gnawing but did not necessarily reduce stress-induced anxiety. Moreover, neuropeptide B (NPB) was expressed in Peri5-projecting PVH neurons, indicating that NPB signaling may mediate the effects of PVH-Peri5. In conclusion, our data revealed a PVH-Peri5 circuit that plays a role in the stress response via its associations with oromotor movements and relative anxiety-like behaviors. [ABSTRACT FROM AUTHOR]

Abstract Self-grooming plays an essential role in hygiene maintenance, thermoregulation, and stress response. However, the neural populations involved in self-grooming remain largely unknown. The paraventricular hypothalamic nucleus (PVH) has been implicated in the regulation of self-grooming. Arginine vasopressin-producing neurons are among the major neuronal populations in the PVH (PVHAVP), which play important roles in water homeostasis, blood pressure regulation, feeding, and stress response. Here, we report the critical role of PVHAVP neurons in the induction of self-grooming. Optogenetic activation of PVHAVP neurons immediately induced self-grooming in freely moving mice. Chemogenetic activation of these neurons also increased time spent self-grooming. In contrast, their chemogenetic inhibition significantly reduced naturally occurring self-grooming, suggesting that PVHAVP-induced grooming has physiological relevance. Notably, optogenetic activation of PVHAVP neurons triggered self-grooming over other adaptive behaviors, such as voracious feeding induced by fasting and social interaction with female mice. Thus, our study proposes the novel role of PVHAVP neurons in regulating self-grooming behavior and, consequently, hygiene maintenance and stress response. Furthermore, uncontrolled activation of these neurons may be potentially relevant to diseases characterized by compulsive behaviors and impaired social interaction, such as autism, obsessive–compulsive disorder, and anorexia nervosa.

Background: The Paraventricular Hypothalamic Nucleus (PVN) coordinates autonomic and neuroendocrine systems to maintain homeostasis. Microinjection of angiotensin II (AngII) into the PVN has been previously shown to produce pressor and bradycardia responses. Anatomical evidence has indicated that a substantial proportion of PVN neurons is connected with the neurons in the central amygdala (CeA). The present study aimed to examine the possible contribution of the CeA in cardiovascular responses evoked by microinjection of AngII into the parvocellular portion of PVN (PVNp) before and after microinjection of cobalt chloride (CoCl2) into the CeA.Methods: The experiments were conducted at the Department of Physiology of Shiraz University of Medical Sciences, from April 2019 to November 2019. There were two groups of 21 eight-week-old urethane anesthetized male rats, namely saline (n=9 rats) and AngII (n=12 rats) groups. Drugs (100 nL) were microinjected via a single-glass micropipette into the PVNp and CeA. Their blood pressure (BP) and heart rate (HR) were recorded throughout the experiments. The mean arterial pressure (MAP) and heart rate (HR) were compared to the pre-injection values using paired t test, and to those of the saline group using independent t test.Results: Microinjection of AngII into the PVNp produced pressor response (P

The paraventricular hypothalamic nucleus (PVH) is an important neuroendocrine center involved in pain regulation, but the nociceptive afferent routes for the nucleus are still unclear. We examined the profile of PVH receiving injurious information by a combination of retrograde tracing with Fluoro-Gold (FG) and FOS expression induced by formalin stimuli. The result showed that formalin injection induced significantly increased expression of FOS in the PVH, among which oxytocin containing neurons are one neuronal phenotype. Immunofluorescent staining of FG and FOS revealed that double labeled neurons were strikingly distributed in the area 2 of the cingulate cortex (Cg2), the lateral septal nucleus (LS), the periaqueductal gray (PAG), the posterior hypothalamic area (PH), and the lateral parabrachial nucleus (LPB). In the five regions, LPB had the biggest number and the highest ratio of FOS expression in FG labeled neurons, with main subnuclei distribution in the external, superior, dorsal, and central parts. Further immunofluorescent triple staining disclosed that about one third of FG and FOS double labeled neurons in the LPB were immunoreactive for calcitonin gene related peptide (CGRP). In conclusion, the present study demonstrates the nociceptive input profile of the PVH area under inflammatory pain and suggests that neurons in the LPB may play essential roles in transmitting noxious information to the PVH. [ABSTRACT FROM AUTHOR]

The dynorphin peptides are the endogenous ligands for the kappa opioid receptor (KOR) and regulate food intake. Administration of dynorphin-A 1-13 (DYN) in the paraventricular hypothalamic nucleus (PVN) increases palatable food intake, and this effect is blocked by co-administration of the orexin-A neuropeptide, which is co-released with DYN in PVN from neurons located in the lateral hypothalamus. While PVN administration of DYN increases palatable food intake, whether it increases food-seeking behaviors has yet to be examined. We tested the effects of DYN and nor BNI (a KOR antagonist) on the seeking and consumption of sucrose using a progressive ratio (PR) and demand curve (DC) tasks. In PVN, DYN did not alter the sucrose breaking point (BP) in the PR task nor the elasticity or intensity of demand for sucrose in the DC task. Still, DYN reduced the delay in obtaining sucrose and increased licks during sucrose intake in the PR task, irrespective of the co-administration of orexin-A. In PVN, nor BNI increased the delay in obtaining sucrose and reduced licks during sucrose intake in the PR task while increasing elasticity without altering intensity of demand in the DC task. However, subcutaneous nor BNI reduced the BP for sucrose and increased the delay in obtaining sucrose in the PR task while reducing the elasticity of demand. Together, these data show different effects of systemic and PVN blockade of KOR on food-seeking, consummatory behaviors, and incentive motivation for sucrose and suggest that KOR activity in PVN is necessary but not sufficient to drive seeking behaviors for palatable food. [ABSTRACT FROM AUTHOR]

Self-grooming plays an essential role in hygiene maintenance, thermoregulation, and stress response. However, the neural populations involved in self-grooming remain largely unknown. The paraventricular hypothalamic nucleus (PVH) has been implicated in the regulation of self-grooming. Arginine vasopressin-producing neurons are among the major neuronal populations in the PVH (PVHAVP), which play important roles in water homeostasis, blood pressure regulation, feeding, and stress response. Here, we report the critical role of PVHAVP neurons in the induction of self-grooming. Optogenetic activation of PVHAVP neurons immediately induced self-grooming in freely moving mice. Chemogenetic activation of these neurons also increased time spent self-grooming. In contrast, their chemogenetic inhibition significantly reduced naturally occurring self-grooming, suggesting that PVHAVP-induced grooming has physiological relevance. Notably, optogenetic activation of PVHAVP neurons triggered self-grooming over other adaptive behaviors, such as voracious feeding induced by fasting and social interaction with female mice. Thus, our study proposes the novel role of PVHAVP neurons in regulating self-grooming behavior and, consequently, hygiene maintenance and stress response. Furthermore, uncontrolled activation of these neurons may be potentially relevant to diseases characterized by compulsive behaviors and impaired social interaction, such as autism, obsessive–compulsive disorder, and anorexia nervosa. [ABSTRACT FROM AUTHOR]

Background: The Paraventricular Hypothalamic Nucleus (PVN) coordinates autonomic and neuroendocrine systems to maintain homeostasis. Microinjection of angiotensin II (AngII) into the PVN has been previously shown to produce pressor and bradycardia responses. Anatomical evidence has indicated that a substantial proportion of PVN neurons is connected with the neurons in the central amygdala (CeA). The present study aimed to examine the possible contribution of the CeA in cardiovascular responses evoked by microinjection of AngII into the parvocellular portion of PVN (PVNp) before and after microinjection of cobalt chloride (CoCl2) into the CeA. Methods: The experiments were conducted at the Department of Physiology of Shiraz University of Medical Sciences, from April 2019 to November 2019. There were two groups of 21 eight-week-old urethane anesthetized male rats, namely saline (n=9 rats) and AngII (n=12 rats) groups. Drugs (100 nL) were microinjected via a single-glass micropipette into the PVNp and CeA. Their blood pressure (BP) and heart rate (HR) were recorded throughout the experiments. The mean arterial pressure (MAP) and heart rate (HR) were compared to the pre-injection values using paired t test, and to those of the saline group using independent t test. Results: Microinjection of AngII into the PVNp produced pressor response (P<0.0001) with no significant changes in HR (P=0.70). Blockade of CeA with CoCl2 attenuated the pressor response to microinjection of AngII into the PVNp (P<0.001). Conclusion: In the PVNp, Ang II increased the rats' blood pressure. This response was in part mediated by the CeA. Our study suggested that these two nuclei cooperate to perform their cardiovascular functions. [ABSTRACT FROM AUTHOR]

Abstract The nucleus of the solitary tract (NTS) plays a crucial role in integrating peripheral information regarding visceral functions. Glutamate decarboxylase 2 (GAD2) inhibitory neurons are abundant in the NTS, and are known to form local and short-range projections within the NTS and nearby hindbrain areas. Here we performed whole-brain mapping of outputs from GAD2 neurons in the NTS using cell-type specific viral labeling together with ultrahigh-speed 3D imaging at 1-μm resolution. In addition to well-known targets of NTS GAD2 neurons including the principle sensory nucleus of the trigeminal (PSV), spinal nucleus of the trigeminal (SPV), and other short-range targets within the hindbrain, the high sensitivity of our system helps reveal previously unknown long-range projections that target forebrain regions, including the bed nuclei of the stria terminalis (BST) involved in stress and fear responses, and the paraventricular hypothalamic nucleus (PVH) involved in energy balance and stress-related neuroendocrine responses. The long-range projections were further verified by retrograde labeling of NTS GAD2 neurons with cholera toxin B (CTB) injections in the BST and PVH, and by Cre-dependent retrograde tracing with rAAV2-retro injections in the two regions of GAD2-Cre mice. Finally, we performed complete morphological reconstruction of several sparsely labeled neurons projecting to the forebrain and midbrain. These results provide new insights about how NTS might participate in physiological and emotional modulation.

The aim of this study was to compare the effect of silver salt and silver nanoparticles on the morphofunctional state of the hypothalamic-adrenal system in obese rats. The experiment was carried out on 24 male rats at the age of 6 months. The rats of the control group received standard food. In other groups of animals, obesity was induced using a diet-induced model of metabolic disorders. The rats, modeled for obesity, were divided into several groups. Animals of different groups received NaCl solution, silver nitrate solution and silver nanoparticle solution for 10 days, respectively. After the end of the experiment, the hypothalamic nuclei and adrenal glands, prepared according to the appropriate histological methods, were taken from the animals. In the paraventricular nucleus of the hypothalamus, a small-cell area of neurons was examined. In the adrenal glands of rats, cells of three zones of the cortex were examined: glomerular, fascicular, and reticular. The results of the study showed that obesity led to the increase of functional activity in the nuclei of neurons in the small-cell region of the PVN of the rat hypothalamus. The cells of the glomerular zone of the adrenal cortex had the maximum increase in functional activity, the fascicular zone – a moderate increase in functional activity, and no significant changes were recorded in the reticular zone. It was shown that the silver salt solution caused the increase in the functional activity of PVN neurons in the hypothalamus of obese rats. In the glomerular zone, the parameters of the functional activity of cells increased significantly, in the fascicular zone, the parameters of cell nuclei decreased to the greater extent, in the reticular zone, mainly the parameters of the nuclei increased. It was investigated that the solution of silver nanoparticles caused the intensification of PVN cells in the hypothalamus of obese rats. In the glomerular zone of the adrenal cortex, a significant increase in cell parameters was observed, in the fascicular zone – the increase in the cytoplasm parameters, in the reticular zone – the decrease mainly in the parameters of cell nuclei. In general, the administration of the solution of silver nanoparticles led to more pronounced activation of PVN cells of the hypothalamus and adrenal cortex in obese rats than the silver salt. [ABSTRACT FROM AUTHOR]

Objective(s): Resistin, as a 12.5 kDa cysteine-rich polypeptide, is expressed in hypothalamus and regulates sympathetic nerve activity. It is associated with obesity, metabolic syndrome and cardiovascular diseases. In this study, we investigated the neural pathway of cardiovascular responses induced by injection of resistin into paraventricular nucleus (PVN) with rostral ventrolateral medulla (RVLM). Materials and Methods: Adult male rats were anesthetized with urethane (1.4 g/kg intraperitoneally). Resistin (3 µg/1 µl/rat) was first injected into PVN, and the glutamatergic, corticotrophin-releasing factor (CRF)-ergic and angiotensinogenic transmission was inhibited by injecting of their antagonist in RVLM. Arterial pressure (AP) and heart rate (HR) were monitored before and after the injection. Results: The results showed that resistin injection into PVN significantly increased AP and HR compared to control group and prior to its injection (PConclusion: It can be concluded that glutamatergic and CRFergic transmissions have crucial contribution to cardiovascular responses produced by resistin. The results provided new and potentially important insight regarding neural transmission when the plasma level of resistin increases; this reveals the role of resistin in cardiovascular responses such as metabolic syndrome and hypertension.

Insomnia and anxiety are two common clinical diseases that threaten people’s physical and mental health. Insomnia and anxiety may share some similar underlying neural circuit mechanisms in the brain. In this study, we combine techniques including chemo-fMRI, optogenetics, and chemogenetics to reveal that the glutamatergic neurons of the paraventricular hypothalamic nucleus (PVN) regulate both anxiety and arousal through two different downstream neural circuits. Optogenetic activation of the PVN-cingulate cortex (Cg) neural circuit triggers anxiety-like behaviors in mice without affecting the wakefulness, while optogenetic activation of the PVN-paraventricular thalamic nucleus (PVT) neural circuit promotes wakefulness in mice without affecting anxiety-like behaviors. Our research reveals that PVN is a key brain area for controlling anxiety and arousal behaviors. We also provide a neurological explanation for anxiety disorder and insomnia which may offer guidance for treatments including drugs or transcranial magnetic stimulation for the patients.

Insomnia and anxiety are two common clinical diseases that threaten people's physical and mental health. Insomnia and anxiety may share some similar underlying neural circuit mechanisms in the brain. In this study, we combine techniques including chemo-fMRI, optogenetics, and chemogenetics to reveal that the glutamatergic neurons of the paraventricular hypothalamic nucleus (PVN) regulate both anxiety and arousal through two different downstream neural circuits. Optogenetic activation of the PVN-cingulate cortex (Cg) neural circuit triggers anxiety-like behaviors in mice without affecting the wakefulness, while optogenetic activation of the PVN-paraventricular thalamic nucleus (PVT) neural circuit promotes wakefulness in mice without affecting anxiety-like behaviors. Our research reveals that PVN is a key brain area for controlling anxiety and arousal behaviors. We also provide a neurological explanation for anxiety disorder and insomnia which may offer guidance for treatments including drugs or transcranial magnetic stimulation for the patients. [ABSTRACT FROM AUTHOR]

[Figure: see text]. [ABSTRACT FROM AUTHOR]

Hypersomnolence disorder (HD) is characterized by excessive sleep, which is a common sequela following stroke, infection, or tumorigenesis. HD is traditionally thought to be associated with lesions of wake-promoting nuclei. However, lesions of a single wake-promoting nucleus, or even two simultaneously, did not exert serious HD. Therefore, the specific nucleus and neural circuitry for HD remain unknown. Here, we observed that the paraventricular nucleus of the hypothalamus (PVH) exhibited higher c-fos expression during the active period (23:00) than during the inactive period (11:00) in mice. Therefore, we speculated that the PVH, in which most neurons are glutamatergic, may represent one of the key arousal-controlling centers. By using vesicular glutamate transporter 2 (vglut2Cre) mice together with fiber photometry, multichannel electrophysiological recordings, and genetic approaches, we found that PVHvglut2 neurons were most active during wakefulness. Chemogenetic activation of PVHvglut2 neurons induced wakefulness for 9 hr, and photostimulation of PVHvglut2→parabrachial complex/ventral lateral septum circuits immediately drove transitions from sleep to wakefulness. Moreover, lesioning or chemogenetic inhibition of PVHvglut2 neurons dramatically decreased wakefulness. These results indicate that the PVH is critical for arousal promotion and maintenance.

Obesity is often associated with aging. However, the mechanism of age-related obesity is unknown. The melanocortin-4 receptor (MC4R) mediates leptin-melanocortin anti-obesity signaling in the hypothalamus. Here, we discovered that MC4R-bearing primary cilia of hypothalamic neurons progressively shorten with age in rats, correlating with age-dependent metabolic decline and increased adiposity. This "age-related ciliopathy" is promoted by overnutrition-induced upregulation of leptin-melanocortin signaling and inhibited or reversed by dietary restriction or the knockdown of ciliogenesis-associated kinase 1 (CILK1). Forced shortening of MC4R-bearing cilia in hypothalamic neurons by genetic approaches impaired neuronal sensitivity to melanocortin and resulted in decreased brown fat thermogenesis and energy expenditure and increased appetite, finally developing obesity and leptin resistance. Therefore, despite its acute anti-obesity effect, chronic leptin-melanocortin signaling increases susceptibility to obesity by promoting the age-related shortening of MC4R-bearing cilia. This study provides a crucial mechanism for age-related obesity, which increases the risk of metabolic syndrome. [Display omitted] • MC4R-bearing primary cilia (MC4R+ cilia) of hypothalamic neurons shorten with age • Shortened MC4R+ cilia blunt satiety signals, leading to obesity and leptin resistance • Chronic leptin-melanocortin signaling promotes obesogenic shortening of MC4R+ cilia • Dietary restriction or Cilk1 knockdown reverses or inhibits MC4R+ ciliary shortening The melanocortin-4 receptor (MC4R) mediates leptin-melanocortin anti-obesity signaling in the hypothalamus. Oya et al. discovered that MC4R-bearing primary cilia of hypothalamic neurons progressively shorten with age to develop age-related obesity and leptin resistance. This "age-related ciliopathy" is promoted by chronic leptin-melanocortin signaling and inhibited by dietary restriction. [ABSTRACT FROM AUTHOR]

The rostral agranular insular cortex (RAIC) is a relevant structure in nociception. Indeed, recruitment of GABAergic activity in RAIC promotes the disinhibition of the locus ceruleus, which in turn inhibits (by noradrenergic action) the peripheral nociceptive input at the spinal cord level. In this regard, at the cortical level, oxytocin can modulate the GABAergic transmission; consequently, an interaction modulating nociception could exist between oxytocin and GABA at RAIC. Here, we tested in male Wistar rats the effect of oxytocin microinjection into RAIC during an inflammatory (by subcutaneous peripheral injection of formalin) nociceptive input. Oxytocin microinjection produces a diminution of (1) flinches induced by formalin and (2) spontaneous firing of spinal wide dynamic range cells. The above antinociceptive effect was abolished by microinjection (at RAIC) of the following: (1) L-368899 (an oxytocin receptor [OTR] antagonist) or by (2) bicuculline (a preferent GABAA receptor blocker), suggesting a GABAergic activation induced by OTR. Since intrathecal injection of an α2A-adrenoceptor antagonist (BRL 44408) partially reversed the oxytocin effect, a descending noradrenergic antinociception is suggested. Further, injection of L-368899 per se induces a pronociceptive behavioral effect, suggesting a tonic endogenous oxytocin release during inflammatory nociceptive input. Accordingly, we found bilateral projections from the paraventricular nucleus of the hypothalamus (PVN) to RAIC. Some of the PVN-projecting cells are oxytocinergic and destinate GABAergic and OTR-expressing cells inside RAIC. Aside from the direct anatomic link between PVN and RAIC, our findings provide evidence about the role of oxytocinergic mechanisms modulating the pain process at the RAIC level. [ABSTRACT FROM AUTHOR]

Oxytocin (OXT) plays important roles in autonomic control and behavioral modulation. However, it is unknown how the projection patterns of OXT neurons align with underlying physiological functions. Here, we present the reconstructed single-neuron, whole-brain projectomes of 264 OXT neurons of the mouse paraventricular hypothalamic nucleus (PVH) at submicron resolution. These neurons hierarchically clustered into two groups, with distinct morphological and transcriptional characteristics and mutually exclusive projection patterns. Cluster 1 (177 neurons) axons terminated exclusively in the median eminence (ME) and have few collaterals terminating within hypothalamic regions. By contrast, cluster 2 (87 neurons) sent wide-spread axons to multiple brain regions, but excluding ME. Dendritic arbors of OXT neurons also extended outside of the PVH, suggesting capability to sense signals and modulate target regions. These single-neuron resolution observations reveal distinct OXT subpopulations, provide comprehensive analysis of their morphology, and lay the structural foundation for better understanding the functional heterogeneity of OXT neurons. [Display omitted] • 3D reconstruction of axon, dendrite, and soma morphologies of single OXT neurons • ME-projecting C1 neurons do not have extrahypothalamic projections • Non-ME-projecting C2 neurons co-project extensively to the endbrain and brainstem • C1 and C2 neurons have distinct morphological and transcriptional characteristics Li et al. 3D reconstructed the complete axon, dendrite, and soma morphologies of individual OXT neurons in the mouse paraventricular hypothalamic nucleus at submicron resolution. They identified two main clusters, which project to mutually exclusive targets and possess distinct morphological features. These results provide a structural foundation for understanding OXT function. [ABSTRACT FROM AUTHOR]

When energy balance is altered by aerobic exercise, starvation, and cold exposure, for example, there appears to be coordination of the responses of skeletal muscle, white adipose (WAT), and brown adipose (BAT) tissues. We hypothesized that WAT, BAT, and skeletal muscle may share an integrated regulation by the central nervous system (CNS); specifically, that neurons in brain regions associated with energy balance would possess neuroanatomical connections to permit coordination of multiple, complementary responses in these downstream tissues. To study this, we used trans‐neuronal viral retrograde tract tracing, using isogenic strains of pseudorabies virus (PRV) with distinct fluorescent reporters (either eGFP or mRFP), injected pairwise into male rat gastrocnemius, subcutaneous WAT and interscapular BAT, coupled with neurochemical characterization of specific cell populations for cocaine‐ and amphetamine‐related transcript (CART), oxytocin (OX), corticotrophin releasing hormone (CRH) and calcitonin gene‐related peptide (CGRP). Cells in the paraventricular (PVN) and parabrachial (PBN) nuclei and brainstem showed dual projections to muscle + WAT, muscle + BAT, and WAT + BAT. Dual PRV‐labeled cells were found in parvocellular, magnocellular and descending/pre‐autonomic regions of the PVN, and multiple structural divisions of the PBN and brainstem. In most PBN subdivisions, more than 50% of CGRP cells dually projected to muscle + WAT and muscle + BAT. Similarly, 31–68% of CGRP cells projected both to WAT + BAT. However, dual PRV‐labeled cells in PVN only occasionally expressed OX or CRH but not CART. These studies reveal for the first time both separate and shared outflow circuitries among skeletal muscle and subcutaneous WAT and BAT. [ABSTRACT FROM AUTHOR]

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Abstract In the brain, various neurotransmitters such as noradrenaline and GABA regulate peripheral sympathetic functions. Previously, it has been reported that both β-adrenoceptor activation and GABA B receptor activation in the brain are involved in the elevation of plasma noradrenaline levels. However, it is unknown whether these pathways interact with each other. In the present study, we examined the relationship between the central actions of β-adrenoceptor activation and GABA B receptor activation with regard to plasma noradrenaline responses using urethane-anesthetized rats. Intracerebroventricular pretreatment with the GABA A receptor antagonist bicuculline did not affect the β-adrenoceptor agonist isoproterenol-induced elevation of plasma noradrenaline levels. In contrast, pretreatment with the GABA B receptor antagonist CGP 35348 suppressed the isoproterenol-induced elevation of noradrenaline levels. Intracerebroventricular pretreatment with the β-adrenoceptor antagonist propranolol did not alter the GABA B receptor agonist baclofen-induced elevation of plasma noradrenaline levels. We next examined the central effects of β-adrenoceptor activation on GABA release in the paraventricular hypothalamic nucleus (PVN), the major integrative center for sympathetic regulation in the brain. Intracerebroventricular administration of isoproterenol increased GABA content in PVN dialysates. In addition, baclofen microinjected unilaterally into the PVN resulted in elevated plasma levels of noradrenaline, but not adrenaline. Finally, unilateral blockade of GABA B receptors in the PVN suppressed the isoproterenol-induced elevation of plasma noradrenaline level. Our results suggest that activation of β-adrenoceptors in the brain, likely in the PVN, induces GABA release in the PVN, which in turn activates GABA B receptors in the PVN, leading to elevated plasma noradrenaline. [ABSTRACT FROM AUTHOR]

Abstract Endocannabinoids and their receptors not only contribute to the control of natural processes of appetite regulation and energy balance but also have an important role in the pathogenesis of obesity. CB1 receptors (CB1R) are expressed in several hypothalamic nuclei, including the paraventricular nucleus (PVN), where induce potent orexigenic responses. Activation of CB1R in the PVN induces hyperphagia by modulating directly or indirectly orexigenic and anorexigenic signals; however, interaction among these mediators has not been clearly defined. CB1R mRNA is expressed in serotonergic neurons that innervate the PVN, and activation of 5-HT receptors in the PVN constitutes an important satiety signal. Some GABAergic terminals are negatively influenced by 5-HT, suggesting that the hyperphagic effect of CB1R activation could involve changes in serotonergic and GABAergic signaling in the PVN. Accordingly, the present study was aimed to characterize the neurochemical mechanisms related to the hyperphagic effects induced by activation of CB1R in the PVN, studying in vitro and in vivo changes induced by direct activation these receptors. Here, we have found that the neurochemical mechanisms activated by stimulation of CB1 receptors in the PVN involve inhibition of 5-HT release, resulting in a decrease of serotonergic activity mediated by 5-HT 1A and 5-HT 1B receptors and inducing disinhibition of GABA release to stimulate food intake. In conclusion, these neurochemical changes in the PVN are determinant to the cannabinoid-induced stimulation of food intake. Our findings provide evidence of a functional connection among CB1R and serotonergic and GABAergic systems on the control of appetite regulation mediated by endocannabinoids. [ABSTRACT FROM AUTHOR]