Calcineurin regulates synaptic Ca2+-permeable AMPA receptors in hypothalamic presympathetic neurons via α2δ-1-mediated GluA1/GluA2 assembly.

Hypertension is a major adverse effect of calcineurin inhibitors, such as tacrolimus (FK506) and cyclosporine, used clinically as immunosuppressants. Calcineurin inhibitor-induced hypertension (CIH) is linked to augmented sympathetic output from the hypothalamic paraventricular nucleus (PVN). GluA2-lacking, Ca2+-permeable AMPA receptors (CP-AMPARs) are a key feature of glutamatergic synaptic plasticity, yet their role in CIH remains elusive. Here, we found that systemic administration of FK506 in rats significantly increased serine phosphorylation of GluA1 and GluA2 in PVN synaptosomes. Strikingly, FK506 treatment reduced GluA1/GluA2 heteromers in both synaptosomes and endoplasmic reticulum-enriched fractions from the PVN. Blocking CP-AMPARs with IEM-1460 induced a larger reduction of AMPAR-mediated excitatory postsynaptic current (AMPAR-EPSC) amplitudes in retrogradely labelled, spinally projecting PVN neurons in FK506-treated rats than in vehicle-treated rats. Furthermore, FK506 treatment shifted the current-voltage relationship of AMPAR-EPSCs from linear to inward rectification in labelled PVN neurons. FK506 treatment profoundly enhanced physical interactions of α2δ-1 with GluA1 and GluA2 in the PVN. Inhibiting α2δ-1 with gabapentin, α2δ-1 genetic knockout, or disrupting α2δ-1-AMPAR interactions with an α2δ-1 C terminus peptide restored GluA1/GluA2 heteromers in the PVN and diminished inward rectification of AMPAR-EPSCs in labelled PVN neurons induced by FK506 treatment. Additionally, microinjection of IEM-1460 or α2δ-1 C terminus peptide into the PVN reduced renal sympathetic nerve discharges and arterial blood pressure elevated in FK506-treated rats but not in vehicle-treated rats. Thus, calcineurin in the hypothalamus constitutively regulates AMPAR subunit composition and phenotypes by controlling GluA1/GluA2 interactions with α2δ-1. Synaptic CP-AMPARs in PVN presympathetic neurons contribute to augmented sympathetic outflow in CIH. KEY POINTS: Systemic treatment with the calcineurin inhibitor increases serine phosphorylation of synaptic GluA1 and GluA2 in the PVN. Calcineurin inhibition enhances the prevalence of postsynaptic Ca2+-permeable AMPARs in PVN presympathetic neurons. Calcineurin inhibition potentiates α2δ-1 interactions with GluA1 and GluA2, disrupting intracellular assembly of GluA1/GluA2 heterotetramers in the PVN. Blocking Ca2+-permeable AMPARs or α2δ-1-AMPAR interactions in the PVN attenuates sympathetic outflow augmented by the calcineurin inhibitor.

Hypothalamic Paraventricular Stimulation Inhibits Nociceptive Wide Dynamic Range Trigeminocervical Complex Cells via Oxytocinergic Transmission.

Oxytocinergic transmission blocks nociception at the peripheral, spinal, and supraspinal levels through the oxytocin receptor (OTR). Indeed, a neuronal pathway from the hypothalamic paraventricular nucleus (PVN) to the spinal cord and trigeminal nucleus caudalis (Sp5c) has been described. Hence, although the trigeminocervical complex (TCC), an anatomical area spanning the Sp5c, C1, and C2 regions, plays a role in some pain disorders associated with craniofacial structures (e.g., migraine), the role of oxytocinergic transmission in modulating nociception at this level has been poorly explored. Hence, in vivo electrophysiological recordings of TCC wide dynamic range (WDR) cells sensitive to stimulation of the periorbital or meningeal region were performed in male Wistar rats. PVN electrical stimulation diminished the neuronal firing evoked by periorbital or meningeal electrical stimulation; this inhibition was reversed by OTR antagonists administered locally. Accordingly, neuronal projections (using Fluoro-Ruby) from the PVN to the WDR cells filled with Neurobiotin were observed. Moreover, colocalization between OTR and calcitonin gene-related peptide (CGRP) or OTR and GABA was found near Neurobiotin-filled WDR cells. Retrograde neuronal tracers deposited at the meningeal (True-Blue, TB) and infraorbital nerves (Fluoro-Gold, FG) showed that at the trigeminal ganglion (TG), some cells were immunopositive to both fluorophores, suggesting that some TG cells send projections via the V1 and V2 trigeminal branches. Together, these data may imply that endogenous oxytocinergic transmission inhibits the nociceptive activity of second-order neurons via OTR activation in CGRPergic (primary afferent fibers) and GABAergic cells.

Single-neuron projectomes of mouse paraventricular hypothalamic nucleus oxytocin neurons reveal mutually exclusive projection patterns.

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.

Oxytocin neurons mediate stress-induced social memory impairment.

Oxytocin has long been thought to play a substantial role in social behaviors, such as social attachment and parenting behavior. However, how oxytocin neurons respond to social and non-social stimuli is largely unknown, especially in high temporal resolution. Here, we recorded the in vivo real-time responses of oxytocin neurons in the paraventricular nucleus of the hypothalamus (PVN) in freely behaving mice. Our results revealed that oxytocin neurons were activated more significantly by stressors than social stimuli. The activation of oxytocin neurons was precisely correlated with struggling behavior during stress. Furthermore, we found that oxytocin mediated stress-induced social memory impairment. Our results reveal an important role of PVN oxytocin neurons in stress-induced social amnesia.

A forebrain-hypothalamic ER stress driven circuit mediates hepatic steatosis during obesity.

OBJECTIVE: Non-alcoholic fatty liver disease (NAFLD) affects 1 in 3 adults and contributes to advanced liver injury and cardiometabolic disease. While recent evidence points to involvement of the brain in NAFLD, the downstream neural circuits and neuronal molecular mechanisms involved in this response, remain unclear. Here, we investigated the role of a unique forebrain-hypothalamic circuit in NAFLD. METHODS: Chemogenetic activation and inhibition of circumventricular subfornical organ (SFO) neurons that project to the paraventricular nucleus of the hypothalamus (PVN; SFO→PVN) in mice were used to study the role of SFO→PVN signaling in NAFLD. Novel scanning electron microscopy techniques, histological approaches, molecular biology techniques, and viral methodologies were further used to delineate the role of endoplasmic reticulum (ER) stress within this circuit in driving NAFLD. RESULTS: In lean animals, acute chemogenetic activation of SFO→PVN neurons was sufficient to cause hepatic steatosis in a liver sympathetic nerve dependent manner. Conversely, inhibition of this forebrain-hypothalamic circuit rescued obesity-associated NAFLD. Furthermore, dietary NAFLD is associated with marked ER ultrastructural alterations and ER stress in the PVN, which was blunted following reductions in excitatory signaling from the SFO. Finally, selective inhibition of PVN ER stress reduced hepatic steatosis during obesity. CONCLUSIONS: Collectively, these findings characterize a previously unrecognized forebrain-hypothalamic-ER stress circuit that is involved in hepatic steatosis, which may point to future therapeutic strategies for NAFLD.

Distinctiveness and continuity in transcriptome and connectivity in the anterior-posterior axis of the paraventricular nucleus of the thalamus.

The paraventricular nucleus of the thalamus (PVT) projects axons to multiple areas, mediates a wide range of behaviors, and exhibits regional heterogeneity in both functions and axonal projections. Still, questions regarding the cell types present in the PVT and the extent of their differences remain inadequately addressed. We applied single-cell RNA sequencing to depict the transcriptomic characteristics of mouse PVT neurons. We found that one of the most significant variances in the PVT transcriptome corresponded to the anterior-posterior axis. While the single-cell transcriptome classified PVT neurons into five types, our transcriptomic and histological analyses showed continuity among the cell types. We discovered that anterior and posterior subpopulations had nearly non-overlapping projection patterns, while another population showed intermediate patterns. In addition, these subpopulations responded differently to appetite-related neuropeptides, with their activation showing opposing effects on food consumption. Our studies unveiled the contrasts and the continuity of PVT neurons that underpin their function.

Endogenous corticotropin-releasing factor potentiates the excitability of presympathetic neurons in paraventricular nucleus via activation of its receptor 1 in spontaneously hypertensive rats.

It is well established that increased excitability of the presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) during hypertension leads to heightened sympathetic outflow and hypertension. However, the mechanism underlying the overactivation of PVN presympathetic neurons remains unclear. This study aimed to investigate the role of endogenous corticotropin-releasing factor (CRF) on the excitability of presympathetic neurons in PVN using Western blot, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) recording, CRISPR/Cas9 technique and patch-clamp technique. The results showed that CRF protein expression in PVN was significantly upregulated in spontaneously hypertensive rats (SHRs) compared with normotensive Wistar-Kyoto (WKY) rats. Besides, PVN administration of exogenous CRF significantly increased RSNA, heart rate and ABP in WKY rats. In contrast, knockdown of upregulated CRF in PVN of SHRs inhibited CRF expression, led to membrane potential hyperpolarization, and decreased the frequency of current-evoked firings of PVN presympathetic neurons, which were reversed by incubation of exogenous CRF. Perfusion of rat brain slices with artificial cerebrospinal fluid containing CRF receptor 1 (CRFR1) blocker, NBI-35965, or CRF receptor 2 (CRFR2) blocker, Antisauvagine-30, showed that blocking CRFR1, but not CRFR2, hyperpolarized the membrane potential and inhibited the current-evoked firing of PVN presympathetic neurons in SHRs. However, blocking CRFR1 or CRFR2 did not affect the membrane potential and current-evoked firing of presympathetic neurons in WKY rats. Overall, these findings indicate that increased endogenous CRF release from PVN CRF neurons enhances the excitability of presympathetic neurons via activation of CRFR1 in SHRs.

The parabrachial nucleus elicits a vigorous corticosterone feedback response to the pro-inflammatory cytokine IL-1ß.

The central nervous system regulates systemic immune responses by integrating the physiological and behavioral constraints faced by an individual. Corticosterone (CS), the release of which is controlled in the hypothalamus by the paraventricular nucleus (PVN), is a potent negative regulator of immune responses. Using the mouse model, we report that the parabrachial nucleus (PB), an important hub linking interoceptive afferent information to autonomic and behavioral responses, also integrates the pro-inflammatory cytokine IL-1ß signal to induce the CS response. A subpopulation of PB neurons, directly projecting to the PVN and receiving inputs from the vagal complex (VC), responds to IL-1ß to drive the CS response. Pharmacogenetic reactivation of these IL-1ß-activated PB neurons is sufficient to induce CS-mediated systemic immunosuppression. Our findings demonstrate an efficient brainstem-encoded modality for the central sensing of cytokines and the regulation of systemic immune responses.

Evidence for a feeding related association between melanocortin in the NTS and Neuropeptide-Y in the PVN.

Melanocortin and neuropeptide-Y (NPY) are both involved in feeding and energy regulation, and they have opposite effects in the paraventricular nucleus of the hypothalamus (PVN). The present study examined an interaction between melanocortin in the nucleus of the solitary tract (NTS) and NPY in the PVN. Male Sprague-Dawley rats were implanted with cannulae in the injection sites of interest. In Experiment 1, subjects received either the melanocortin 3/4-receptor (MC3/4) antagonist SHU9119 (0, 10, 50 and 100 pmol/0.5 µl) or the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 µl) into the NTS. Food intake was measured at 1, 2, 4, 6 and 24-h post-injection. Administration of SHU9119 into the NTS significantly and dose-dependently increased food intake at 1, 2, 4, 6 and 6-24-h, and administration of MTII into the NTS significantly and dose-dependently decreased 24-h free feeding. In Experiment 2, subjects received the MC3/4 agonist MTII (0, 10, 50, 100 and 200 pmol/0.5 µl) into the NTS just prior to NPY (0 and 1µg/0.5 µl) in the PVN. PVN injection of NPY stimulated feeding, and administration of MTII (50, 100 and 200 pmol) into the NTS significantly and dose-dependently decreased NPY-induced feeding at 2, 4, 6 and 6-24-h. These data suggest that there could be a neuronal association between melanocortin in the NTS and NPY in the PVN, and that the melanocortin system in the NTS has an antagonistic effect on NPY-induced feeding in the PVN.

The paraventricular nucleus of the hypothalamus - the concertmaster of autonomic control. Focus on blood pressure regulation.

The autonomic nervous system regulates internal organs and peripheral circulation, which enables the maintenance of homeostasis in vertebrate species. One of the brain regions involved in autonomic and endocrine homeostasis regulation is the paraventricular nucleus of the hypothalamus (PVN). The PVN is a unique site at which multiple input signals can be assessed and integrated. The regulation of the autonomic system by the PVN and, especially, the sympathetic flow, depends upon the integration of inhibitory and excitatory neurotransmitter action. The excitatory neurotransmitters such as glutamate and angiotensin II, and inhibitory neurotransmitters such as γ­aminobutyric acid and nitric oxide, play a key role in the physiological function of the PVN. Moreover, arginine-vasopressin (AVP) and oxytocin (OXT) are important in the regulation of sympathetic system activity. The PVN is also crucial for maintaining cardiovascular regulation, with its integrity being pivotal for blood pressure regulation. Studies have shown that pre­autonomic sympathetic PVN neurons increase blood pressure and the dysfunction of these neurons is directly related to elevated sympathetic nervous system activity under hypertension. Etiology of hypertension in patients is not fully known. Thus, understanding the role of PVN in the generation of hypertension may help to treat this cardiovascular disease. This review focuses on the PVN's inhibitory and excitatory neurotransmitter interactions that regulate sympathetic system activity in physiological conditions and hypertension.

Molecular and cellular mechanisms of the first social relationship: A conserved role of 5-HT from mice to monkeys, upstream of oxytocin.

Maternal affiliation by infants is the first social behavior of mammalian animals. We report here that elimination of the Tph2 gene essential for serotonin synthesis in the brain reduced affiliation in mice, rats, and monkeys. Calcium imaging and c-fos immunostaining showed maternal odors activation of serotonergic neurons in the raphe nuclei (RNs) and oxytocinergic neurons in the paraventricular nucleus (PVN). Genetic elimination of oxytocin (OXT) or its receptor reduced maternal preference. OXT rescued maternal preference in mouse and monkey infants lacking serotonin. Tph2 elimination from RN serotonergic neurons innervating PVN reduced maternal preference. Reduced maternal preference after inhibiting serotonergic neurons was rescued by oxytocinergic neuronal activation. Our genetic studies reveal a role for serotonin in affiliation conserved from mice and rats to monkeys, while electrophysiological, pharmacological, chemogenetic, and optogenetic studies uncover OXT downstream of serotonin. We suggest serotonin as the master regulator upstream of neuropeptides in mammalian social behaviors.

Opioid Receptors Modulate Firing and Synaptic Transmission in the Paraventricular Nucleus of the Thalamus.

The paraventricular nucleus of the thalamus (PVT) is involved in drug addiction-related behaviors, and morphine is a widely used opioid for the relief of severe pain. Morphine acts via opioid receptors, but the function of opioid receptors in the PVT has not been fully elucidated. Here, we used in vitro electrophysiology to study neuronal activity and synaptic transmission in the PVT of male and female mice. Activation of opioid receptors suppresses the firing and inhibitory synaptic transmission of PVT neurons in brain slices. On the other hand, the involvement of opioid modulation is reduced after chronic morphine exposure, probably because of desensitization and internalization of opioid receptors in the PVT. Overall, the opioid system is essential for the modulation of PVT activities.SIGNIFICANCE STATEMENT Opioid receptors modulate the activities and synaptic transmission in the PVT by suppressing the firing rate and inhibitory synaptic inputs. These modulations were largely diminished after chronic morphine exposure.

PVH-Peri5 Pathway for Stress-Coping Oromotor and Anxious Behaviors in Mice.

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.

A paraventricular hypothalamic nucleus input to ventral of lateral septal nucleus controls chronic visceral pain.

ABSTRACT: Irritable bowel syndrome is a functional gastrointestinal disorder characterized by chronic visceral pain with complex etiology and difficult treatment. Accumulated evidence has confirmed that the sensitization of the central nervous system plays an important role in the development of visceral pain, whereas the exact mechanisms of action of the neural pathways remain largely unknown. In this study, a distinct neural circuit was identified from the paraventricular hypothalamic (PVH) to the ventral of lateral septal (LSV) region. This circuit was responsible for regulating visceral pain. In particular, the data indicated that the PVH CaMKIIα-positive neurons inputs to the LSV CaMKIIα-positive neurons were only activated by colorectal distention rather than somatic stimulations. The PVH-LSV CaMKIIα + projection pathway was further confirmed by experiments containing a viral tracer. Optogenetic inhibition of PVH CaMKIIα + inputs to LSV CaMKIIα-positive neurons suppressed visceral pain, whereas selective activation of the PVH-LSV CaMKIIα + projection evoked visceral pain. These findings suggest the critical role of the PVH-LSV CaMKIIα + circuit in regulating visceral pain.

Endogenous corticotropin-releasing factor potentiates the excitability of presympathetic neurons in paraventricular nucleus via activation of its receptor 1 in spontaneously hypertensive rats / 生理学报

It is well established that increased excitability of the presympathetic neurons in the hypothalamic paraventricular nucleus (PVN) during hypertension leads to heightened sympathetic outflow and hypertension. However, the mechanism underlying the overactivation of PVN presympathetic neurons remains unclear. This study aimed to investigate the role of endogenous corticotropin-releasing factor (CRF) on the excitability of presympathetic neurons in PVN using Western blot, arterial blood pressure (ABP) and renal sympathetic nerve activity (RSNA) recording, CRISPR/Cas9 technique and patch-clamp technique. The results showed that CRF protein expression in PVN was significantly upregulated in spontaneously hypertensive rats (SHRs) compared with normotensive Wistar-Kyoto (WKY) rats. Besides, PVN administration of exogenous CRF significantly increased RSNA, heart rate and ABP in WKY rats. In contrast, knockdown of upregulated CRF in PVN of SHRs inhibited CRF expression, led to membrane potential hyperpolarization, and decreased the frequency of current-evoked firings of PVN presympathetic neurons, which were reversed by incubation of exogenous CRF. Perfusion of rat brain slices with artificial cerebrospinal fluid containing CRF receptor 1 (CRFR1) blocker, NBI-35965, or CRF receptor 2 (CRFR2) blocker, Antisauvagine-30, showed that blocking CRFR1, but not CRFR2, hyperpolarized the membrane potential and inhibited the current-evoked firing of PVN presympathetic neurons in SHRs. However, blocking CRFR1 or CRFR2 did not affect the membrane potential and current-evoked firing of presympathetic neurons in WKY rats. Overall, these findings indicate that increased endogenous CRF release from PVN CRF neurons enhances the excitability of presympathetic neurons via activation of CRFR1 in SHRs.

Central Nucleus of Amygdala Mediate Pressor Response Elicited by Microinjection of Angiotensin II into the Parvocellular Paraventricular Nucleus in Rats.

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.

Brain motor and fear circuits regulate leukocytes during acute stress.

The nervous and immune systems are intricately linked1. Although psychological stress is known to modulate immune function, mechanistic pathways linking stress networks in the brain to peripheral leukocytes remain poorly understood2. Here we show that distinct brain regions shape leukocyte distribution and function throughout the body during acute stress in mice. Using optogenetics and chemogenetics, we demonstrate that motor circuits induce rapid neutrophil mobilization from the bone marrow to peripheral tissues through skeletal-muscle-derived neutrophil-attracting chemokines. Conversely, the paraventricular hypothalamus controls monocyte and lymphocyte egress from secondary lymphoid organs and blood to the bone marrow through direct, cell-intrinsic glucocorticoid signalling. These stress-induced, counter-directional, population-wide leukocyte shifts are associated with altered disease susceptibility. On the one hand, acute stress changes innate immunity by reprogramming neutrophils and directing their recruitment to sites of injury. On the other hand, corticotropin-releasing hormone neuron-mediated leukocyte shifts protect against the acquisition of autoimmunity, but impair immunity to SARS-CoV-2 and influenza infection. Collectively, these data show that distinct brain regions differentially and rapidly tailor the leukocyte landscape during psychological stress, therefore calibrating the ability of the immune system to respond to physical threats.

Excitatory neurons in paraventricular hypothalamus contributed to the mechanism underlying acupuncture regulating the swallowing function.

Paraventricular hypothalamus (PVH) is demonstrated to regulate stress, feeding behaviors, and other related homeostatic processes. However, no direct evidence has been investigated for the role of PVH in swallowing function. Acupuncture therapy at Lianquan (CV23) acupoint has been reported to improve the swallowing function in clinical trials, but its underlying mechanism still needs to be uncovered. Thus, we aimed to explore whether PVH involved the acupuncture mediated regulating swallowing function. Chemogenetics, electromyography (EMG) recording, and immunofluorescence staining methods were combined to demonstrate that neurons in PVH could be activated by electroacupuncture (EA) stimulation at CV23, and this neuronal cluster was represented as excitatory neurons. Furthermore, we mapped both the inputs and outputs of PVH neurons using viral tracing. The neurons in PVH projected with the brain regions, including parabrachial nucleus (PBN) and the solitary tract nucleus (NTS), which both participated in the swallowing process. The EA function regulating the swallowing was attenuated after inhibiting the neurons in PVH in the post stroke dysphagia. In conclusion, this study suggested that EA at CV23 could regulate swallowing function involving the excitatory neurons in PVH.

A Critical Role for the Paraventricular Nucleus of the Hypothalamus in the Regulation of the Volume Reflex in Normal and Various Cardiovascular Disease States.

PURPOSE OF REVIEW: This review focuses on studies implicating forebrain neural pathways and neuromodulator systems, particularly, the nitric oxide system within the paraventricular nucleus of the hypothalamus in regulating neurohumoral drive, autonomic pathways, and fluid balance. RECENT FINDINGS: Accumulating evidence from animals with experimental models of hypertension and heart failure as well as humans with hypertension suggests that alterations in central neural pathways, particularly, within the PVN neuromodulated by neuronal nitric oxide, are involved in regulating sympathetic outflow particularly to the kidney resulting in alterations in fluid balance commonly observed in hypertension and heart failure states. The characteristics of the hypertensive and heart failure states include alterations in neuronal nitric oxide within the PVN to cause an increase in renal sympathetic nerve activity to result in sodium and fluid retention in these diseases. A comprehensive understanding of these mechanisms will enhance our ability to treat hypertensive and heart failure conditions and their cardiovascular complications more efficiently.

Morpho-Electric Properties and Diversity of Oxytocin Neurons in Paraventricular Nucleus of Hypothalamus in Female and Male Mice.

Oxytocin (OXT) neurons in paraventricular nucleus of hypothalamus (PVN) are involved in modulating multiple functions, including social, maternal, feeding, and emotional related behaviors. PVN OXT neurons are canonically classified into magnocellular (Magno) and parvocellular (Parvo) subtypes. However, morpho-electric properties and the diversity of PVN OXT neurons are not well investigated. In this study, we profiled the morpho-electric properties of PVN OXT neurons by combining transgenic mice, electrophysiological recording, morphologic reconstruction, and unsupervised clustering analyses. Total 224 PVN OXT neurons from 23 mice were recorded and used for analyses in this study, and 29 morpho-electric parameters were measured. Magno and Parvo OXT neurons have prominent differences in their morpho-electric features, and PVN OXT neurons in male and female mice share similar neuronal properties. Some morpho-electric features of PVN OXT neurons, especially Magno neurons, exhibit significant diverse changes along the rostral-caudal axis. Furthermore, we find that PVN OXT neurons are classified into at least six subtypes based on their morpho-electric properties via unsupervised clustering. Only one Magno-Parvo mixed subtype in posterior PVN subregion, but not the other five subtypes, showed significant neuronal activity change in different feeding conditions. Our study supports the diversity of PVN OXT neurons and subtle neuron classification will promote excavating the functions of oxytocinergic system.SIGNIFICANCE STATEMENT Oxytocin (OXT) is well known for its function in labor induction, but it also plays multiple roles in social, feeding, and emotional behaviors via modulating different brain regions. Paraventricular nucleus of hypothalamus (PVN) OXT neurons are traditionally classified into magnocellular and parvocellular. However, functional and single-cell transcriptomic studies indicate that OXT neurons should be further classified. Here, we thoroughly investigated the morpho-electric properties and spatial distribution of PVN OXT neurons, and find that OXT neurons have at least six subtypes based on their morpho-electric features. Among these six subtypes, only one magnocellular-parvocellular mixed subtype, which are distributed in the posterior PVN subregion, change their activities with different feeding states. Our study uncovers the diversity of PVN OXT neurons and suggests the necessary of subtle neuronal classification.