Activity In Paraventricular Nucleus Research Articles

Modulating activity of PVN neurons prevents atrial fibrillation induced circulation dysfunction by electroacupuncture at BL15

BackgroundCirculation dysfunction is a major contributing factor to thrombosis in patients with atrial fibrillation (AF) for which effective interventions are lacking. Growing evidence indicates that regulating the paraventricular nucleus (PVN), an autonomic control center, could offer a novel strategy for treating cardiovascular and circulatory diseases. Concurrently, electroacupuncture (EA) at Xinshu (BL15), a form of peripheral nerve stimulation, has shown efficacy in treating several cardiovascular conditions, although its specific mechanism remains unclear. This study aimed to assess the impact of EA at BL15 on circulatory dysfunction in a rat AF model and investigate the pivotal role of PVN neuronal activity.MethodsTo mimic the onset of AF, male SD rats received tail intravenous injection of ACh-CaCl2 and were then subjected to EA at BL15, sham EA, or EA at Shenshu (BL23). Macro- and micro-circulation function were evaluated using in vivo ultrasound imaging and laser doppler testing, respectively. Vasomotricity was assessed by measuring dimension changes during vascular relaxation and contraction. Vascular endothelial function was measured using myograph, and the activation of the autonomic nerve system was evaluated through nerve activity signals. Additionally, chemogenetic manipulation was used to block PVN neuronal activation to further elucidate the role of PVN activation in the prevention of AF-induced blood circulation dysfunction through EA treatment.ResultsOur data demonstrate that EA at BL15, but not BL23 or sham EA, effectively prevented AF-induced macro- and micro-circulation dysfunction. Furthermore, EA at BL15 restored AF-induced vasomotricity impairment. Additionally, EA treatment prevented abnormal activation of the autonomic nerve system induced by AF, although it did not address vascular endothelial dysfunction. Importantly, excessive activation of PVN neurons negated the protective effects of EA treatment on AF-induced circulation dysfunction in rats.ConclusionThese results indicate that EA treatment at BL15 modulates PVN neuronal activity and provides protection against AF-induced circulatory dysfunction.

Microglia activation in paraventricular nucleus of hypothalamus: A self-help strategy for fetus born to preeclamptic mother

Preeclampsia (PE) is a life-threatening pregnancy-specific disorder, characterized by new-onset hypertension after 20 weeks of gestation. It has been generally acknowledged that failure of uterine spiral arteries remodeling, imbalance of pro-angiogenic and anti-angiogenic substances are engaged in the early stage of PE. Nevertheless, the exact pathogenesis remains poorly understood. Recent evidence shows that microglial activation in the paraventricular nucleus of hypothalamus (PVN) is associated with neuroinflammation and enhanced sympathetic excitation, which contribute to the hypertensive status in many diseases with PE included. In our recent work, we sequenced fetus-derived exosomal microRNA (miRNA) profiles and found that 181 miRNAs were significantly downregulated in women with PE. Among these miRNAs, miR-216a-5p exhibited the most significant fold change and may regulate CCCTC-binding factor (ctcf), the pivotal molecule in microglia activation. In conclusion, we hypothesize that fetuses under compromised uteroplacental environment may release exosomal miRNAs, activate microglia in maternal PVN, enhance sympathetic excitation and result in elevated maternal blood pressure, which participate in the occurrence and development of PE, however, guarantee the adequate blood supply to fetuses themselves. More basic research regarding this hypothesis may open up a new direction for the study of the pathogenesis of PE and is expected to provide a new theoretical basis for early diagnosis and treatment of PE. One day, would the changes of specific miRNAs be discovered through portable device may help the early diagnosis of PE or be the marker of prognosis of worsened PE.

Anthocyanin attenuates high salt-induced hypertension via inhibiting the hyperactivity of the sympathetic nervous system

ABSTRACT Background Anthocyanin plays a protective role in cardiovascular disease through antioxidant effect. Whether anthocyanin can reduce salt-induced hypertension and the related mechanisms remain unclear. Methods Chronic infusion of vehicle (artificial cerebrospinal fluid, aCSF, 0.4 μL/h) or anthocyanin (10 mg/kg, 0.4 μL/h) into bilateral paraventricular nucleus (PVN) of Sprague-Dawley rats was performed. Then, the rats were fed a high salt diet (8% NaCl, HS) or normal salt diet (0.9%, NaCl, NS) for 4 weeks. Results High salt diet induced an increase in blood pressure and peripheral sympathetic nerve activity (increased LF/HF and decreased SDNN and RMSSD), which was accompanied by increased reactive oxygen species (ROS) production and angiotensin II type-1 receptor (AT1R) expression and function in the PVN. Moreover, the NOD-like receptor protein 3 (NLRP3) and related inflammatory proteins (caspase-1) expression, the pro-inflammatory cytokine levels including IL-1β and TNF-α were higher in PVN of rats with a high salt diet. Bilateral PVN infusion of anthocyanin attenuated NLRP3-dependent inflammation (NLRP3, caspase-1, IL-1β and TNF-α) and ROS production, reduced AT1R expression and function in PVN and lowered peripheral sympathetic nerve activity and blood pressure in rats with salt-induced hypertension. Conclusions Excessive salt intake activates NLRP3-dependent inflammation and oxidative stress and increased AT1R expression and function in the PVN. Bilateral PVN infusion of anthocyanin lowers peripheral sympathetic nerve activity and blood pressure in rats with salt-induced hypertension by improvement of expression and function of AT1R in the PVN through inhibiting NLRP3 related inflammatory and oxidative stress.

High-Fat Diet Modulates the Excitability of Neurons within the Brain-Liver Pathway.

Stimulation of hepatic sympathetic nerves increases glucose production and glycogenolysis. Activity of pre-sympathetic neurons in the paraventricular nucleus (PVN) of the hypothalamus and in the ventrolateral and ventromedial medulla (VLM/VMM) largely influence the sympathetic output. Increased activity of the sympathetic nervous system (SNS) plays a role in the development and progression of metabolic diseases; however, despite the importance of the central circuits, the excitability of pre-sympathetic liver-related neurons remains to be determined. Here, we tested the hypothesis that the activity of liver-related neurons in the PVN and VLM/VMM is altered in diet-induced obese mice, as well as their response to insulin. Patch-clamp recordings were conducted from liver-related PVN neurons, VLM-projecting PVN neurons, and pre-sympathetic liver-related neurons in the ventral brainstem. Our data demonstrate that the excitability of liver-related PVN neurons increased in high-fat diet (HFD)-fed mice compared to mice fed with control diet. Insulin receptor expression was detected in a population of liver-related neurons, and insulin suppressed the firing activity of liver-related PVN and pre-sympathetic VLM/VMM neurons in HFD mice; however, it did not affect VLM-projecting liver-related PVN neurons. These findings further suggest that HFD alters the excitability of pre-autonomic neurons as well as their response to insulin.

Hypothalamic Paraventricular Nucleus Hydrogen Sulfide Exerts Antihypertensive Effects in Spontaneously Hypertensive Rats via the Nrf2 Pathway.

Hydrogen sulfide (H2S) is widely distributed throughout the nervous system with various antioxidant and anti-inflammatory properties. Hypertension involves an increase in reactive oxygen species (ROS) and inflammation in the hypothalamic paraventricular nucleus (PVN). However, it is unclear how H2S in PVN affects hypertension. Our study used spontaneously hypertensive rats (SHR) and control Wistar Kyoto (WKY) rats, microinjected with adenovirus-associated virus (AAV)-CBS (cystathionine beta-synthase overexpression) or AAV-ZsGreen in bilateral PVN, or simultaneously injected with virus-carrying nuclear factor erythroid 2-related factor 2 (Nrf2)-shRNA for 4 weeks. Blood pressure (BP) and plasma noradrenaline level were detected, and the PVN was collected. Finally, levels of CBS, H2S, Nrf2, Fra-LI, ROS, gp91phox, p47phox, superoxide dismutase 1, interleukin (IL)-1β, IL-6, IL-10, tumor necrosis factor-α, tyrosine hydroxylase, and glutamate decarboxylase 67 were measured. We found that AAV-CBS increased H2S in the PVN, and BP, neuronal activation, oxidative stress, and inflammation of PVN were substantially reduced. Furthermore, endogenous H2S in the PVN activated Nrf2 and corrected the PVN's imbalance of excitatory and inhibitory neurotransmitters. However, Nrf2 knockdown in the PVN was similarly observed to abolish the beneficial effect of H2S on hypertension. The findings imply that endogenous H2S in SHR PVN is reduced, and PVN endogenous H2S can alleviate hypertension via Nrf2-mediated antioxidant and anti-inflammatory effects.

Effects of chronic mild stress on GABAergic system in the paraventricular nucleus of hypothalamus associated with cardiac autonomic activity

Stress is associated with cardiovascular diseases. One possible mechanism is the reduction in gamma-aminobutyric acid (GABA)ergic transmission at the paraventricular nucleus (PVN), which contributes to the disinhibition of sympathoexcitatory circuits and activates sympathetic outflow. At present, the mechanism of chronic mild stress (CMS) on GABAergic transmission at the PVN and cardiac autonomic activity is not yet fully clarified. Therefore, this study was designed to investigate the effects of CMS on the GABAergic system at the PVN and on the cardiac autonomic activity. Adult male Sprague–Dawley rats were randomly assigned to control (left undisturbed in their home cage) or CMS (subjected to various mild stressors for 4 weeks). Cardiac autonomic activities were determined by heart rate variability (HRV) analysis, and GABAergic alterations at the PVN were determined from GABA levels and mRNA expression of GABA-related activities. Results showed that the CMS group had decreased HRV as determined by the standard deviation of all R–R intervals (SDNN). The low frequency (LF) and high frequency (HF) powers of the CMS group were higher than those of the control. Hence, the LF/HF ratio was consequently unaffected. These findings indicated that despite the increase in sympathetic and parasympathetic activities, the autonomic balance was preserved at 4 weeks post CMS. For the GABAergic-related parameters, the CMS group had decreased mRNA expression of glutamic acid decarboxylase-65 (GAD-65), the GABA-synthesizing enzyme, and increased mRNA expression of gamma-aminobutyric acid transporter-1 (GAT-1). Moreover, the GAD-65 mRNA expression was negatively correlated with LF. In conclusion, 4-week CMS exposure in male rats could attenuate GABAergic transmission at the PVN and alter cardiac autonomic activities.

Salusin-β in Intermediate Dorsal Motor Nucleus of the Vagus Regulates Sympathetic-Parasympathetic Balance and Blood Pressure.

The dorsal motor nucleus of the vagus (DMV) is known to control vagal activity. It is unknown whether the DMV regulates sympathetic activity and whether salusin-β in the DMV contributes to autonomic nervous activity. We investigated the roles of salusin-β in DMV in regulating sympathetic-parasympathetic balance and its underline mechanisms. Microinjections were carried out in the DMV and hypothalamic paraventricular nucleus (PVN) in male adult anesthetized rats. Renal sympathetic nerve activity (RSNA), blood pressure and heart rate were recorded. Immunohistochemistry for salusin-β and reactive oxidative species (ROS) production in the DMV were examined. Salusin-β was expressed in the intermediate DMV (iDMV). Salusin-β in the iDMV not only inhibited RSNA but also enhanced vagal activity and thereby reduced blood pressure and heart rate. The roles of salusin-β in causing vagal activation were mediated by NAD(P)H oxidase-dependent superoxide anion production in the iDMV. The roles of salusin-β in inhibiting RSNA were mediated by not only the NAD(P)H oxidase-originated superoxide anion production in the iDMV but also the γ-aminobutyric acid (GABA)A receptor activation in PVN. Moreover, endogenous salusin-β and ROS production in the iDMV play a tonic role in inhibiting RSNA. These results indicate that salusin-β in the iDMV inhibits sympathetic activity and enhances vagal activity, and thereby reduces blood pressure and heart rate, which are mediated by NAD(P)H oxidase-dependent ROS production in the iDMV. Moreover, GABAA receptor in the PVN mediates the effect of salusin-β on sympathetic inhibition. Endogenous salusin-β and ROS production in the iDMV play a tonic role in inhibiting sympathetic activity.

Differential paraventricular nucleus activation and behavioral responses to social isolation in prairie voles following environmental enrichment with and without physical exercise

ABSTRACT Social stressors produce neurobiological and emotional consequences in social species. Environmental interventions, such as environmental enrichment and exercise, may modulate physiological and behavioral stress responses. The present study investigated the benefits of environmental enrichment and exercise against social stress in the socially monogamous prairie vole. Female prairie voles remained paired with a sibling (control) or were isolated from a sibling for 4 weeks. The isolated groups were assigned to isolated sedentary, isolated with environmental enrichment, or isolated with both enrichment and exercise conditions. Behaviors related to depression, anxiety, and sociality were investigated using the forced swim test (FST), elevated plus maze (EPM), and a social crowding stressor (SCS), respectively. cFos expression was evaluated in stress-related circuitry following the SCS. Both enrichment and enrichment with exercise protected against depression-relevant behaviors in the FST and social behavioral disruptions in the SCS, but only enrichment with exercise protected against anxiety-related behaviors in the EPM and altered cFos expression in the hypothalamic paraventricular nucleus in isolated prairie voles. Enrichment may improve emotion-related and social behaviors, however physical exercise may be an important component of environmental strategies for protecting against anxiety-related behaviors and reducing neural activation as a function of social stress.

PVN ‐ projecting MnPO neurons are involved in blood pressure and sympathetic nerve activity regulation in CIH hypertension

Sleep apnea (SA) is characterized by repeated interruptions in breathing resulting in hypoxia, hypercapnia, and increased thoracic pressure. Chronic intermittent hypoxia (CIH) in rats mimics the repetitive hypoxemias that occur with SA leading to a sustained increase in blood pressure associated with increased sympathetic activity and chemoreceptor sensitivity. CIH increases the peripheral renin-angiotensin system (RAS) activating the subfornical organ (SFO) which in turn projects to the hypothalamic paraventricular nucleus (PVN) and the median preoptic nucleus (MnPO). Angiotensin receptor knockdown in SFO or MnPO neurons and virally –mediated caspase lesions PVN-projecting MnPO neurons prevents CIH hypertension. These results suggest that PVN-projecting MnPO neurons play a significant role in blood pressure regulation in CIH hypertension. However, the contribution of MnPO to increased sympathetic nerve activity in CIH hypertension has not been directly tested. Our hypothesis is that the chronic activation of PVN by SFO via MnPO contributes to increased sympathetic outflow sustaining CIH hypertension through the diurnal cycle. In order to selectively inhibit PVN-projecting MnPO neurons, a retrograde Cre-dependent virus was microinjected bilaterally into PVN (AAV9.hSyn.HI.eGFP-Cre.WPRE.SV40) and a Cre-dependent inhibitory DREADD (PAAV.Syn.DIO.hM4D(Gi)-mCherry) was injected into MnPO. Two weeks later, rats were submitted to a 7-day CIH protocol (3 min of 10% oxygen followed by 3 min of 21% oxygen, 8 h/day) or normoxia. Rats were anesthetized (urethane 800 mg/kg and α-chloralose 80 mg/kg ip) and the trachea was cannulated for artificial ventilation. A femoral vein catheter (PE-50 tubing) was implanted for continuous infusion of gallamine triethiodide (20 mg/mL, 0.25 mL/h iv) for neuromuscular blockade. Blood pressure was measured by a Millar catheter system in the femoral artery. The rats were placed in a stereotaxic frame and a craniotomy was performed for intracerebroventricular (ICV) injections. Renal and splanchnic nerves were isolated and placed in a bipolar electrode. Noise levels were determined after a bolus injection of hexamethonium (30 mg/kg iv). Using a pneumatic picopump (WPI) connected to a single-barreled glass micropipette, DREADD agonist CNO (1µg/1µl) was injected ICV and responses were collected after 30 min of the injection. In rats exposed to normoxia, chemogenetic inhibition of PVN-projecting MnPO neurons slightly increased splanchnic SNA (4.9±21, n=3), renal SNA (17± 17, n=3) and increased blood pressure (Normoxia: 4.3±4, n=3; CIH; -0.3± 4, n=3). In rats exposed to CIH, CNO reduced splanchnic SNA (-42.9±37, n=4) and renal SNA (-88±49, n=3). These preliminary results suggest that CIH triggers a neuroadaptation that changes the relationship between the SFO-MnPO-PVN pathway and SNA.

Relaxin increased blood pressure and sympathetic activity in paraventricular nucleus of hypertensive rats via enhancing oxidative stress

Relaxin, an ovarian polypeptide hormone, is found in the hypothalamic paraventricular nucleus (PVN) which is an important central integrative site for the control of blood pressure and sympathetic outflow. The aim of this study was to determine if superoxide anions modulate the effects of relaxin in the PVN. Experiments were performed in normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHRs). Relaxin mRNA and protein, and its receptor, relaxin family peptide receptor 1 (RXFP1) levels in PVN were 3.24, 3.17, and 3.64 times higher in SHRs than in WKY rats, respectively. Microinjection of relaxin-2 into the PVN dose-dependently increased mean arterial pressure (MAP), renal sympathetic nerve activity (RSNA) and heart rate (HR) in both WKY rats and SHRs, although the effects on MAP (16.87 ± 1.99 vs. 8.97 ± 1.48 mm Hg in 100 nmol), RSNA (22.60 ± 2.15 vs. 11.77 ± 1.43 % in 100 nmol) and HR (22.85 ± 3.13 vs. 12.62 ± 2.83 beats/min in 100 nmol) were greater in SHRs. Oxidative stress level was enhanced after relaxin-2 microinjection into the PVN. Pretreatment with superoxide anion scavengers or NADPH oxidase inhibitor blocked, and superoxide dismutase inhibitor potentiated the effects of relaxin-2 on MAP, RSNA and HR. RXFP1 knockdown significantly attenuated the blood pressure of SHRs, and inhibited the increases of atrial natriuretic peptide, brain natriuretic peptide, collagen I, collagen III and fibronectin in the heart of SHRs. These results demonstrated that relaxin is expressed in the PVN, and contributes to hypertension and sympathetic overdrive via oxidative stress. Down-regulation of RXFP1 in the PVN could attenuate hypertension and cardiac remodeling.

Hypothalamic aging and hormones.

It is the heterogeneous changes of hypothalamic functions that determine the chronological sequence of aging in mammals. Recently, it was hypothesized by Cai the decrease in slow-wave sleep (SWS) resulting from skin aging as responsible for the degeneration of hypothalamic suprachiasmatic nucleus (SCN). It was soon hypothesized by the European people in television that the increase in body fat as responsible for the degeneration of male preoptic sexually dimorphic nucleus (SDN-POA), via the aromatase converting testosterone to estradiol as proposed by Cohen. It is the hypothalamic paraventricular nucleus (PVN) that remains unchanged in neuron number during aging for psychological stress. In this chapter, it is briefly reviewed more manifestations of hypothalamic related mammalian aging processes, including (1) the aging of ovary by lipid, estradiol and hypothalamus; (2) the aging of muscle, stomach, intestine, thymus, and the later aging of brain, regulated by growth hormone/insulin-like growth factor 1(GH/IGF1); (3) the cardiovascular hypertension from PVN activation, the bone and other peripheral aging by psychological stress, and that of kidney by vasopressin. It is classified these aging processes by the primary regulation from one of the three hypothalamic nuclei, although still necessary to investigate and supplement their secondary regulation by the hypothalamic nuclei in future. It is the hypothalamic structural changes that shift the functional balance among these three hypothalamic systems toward aging.

<p><strong>Polyphenol rich extract from <em>Sesbania grandiflora</em> (L.) Pers. bark reduces rheumatism by mediating the expression of NF kappa B in rats</strong></p>

Sesbania grandiflora (L . ) Pers. (Fabaceae) commonly called Agati or Vegetable Hummingbird, is autochthonal from Malaysia to North Australia; plant is cultivated in several parts of India. Root and bark paste is applied externally to relive pain and inflammation associated with arthritis. It has long been used as a traditional medicine for rheumatism. Keeping this in cognizance, the study was designed to explore the antirheumatic potential of S. grandiflora. The bark extracts were prepared and studied for their phytochemical study, in vitro antioxidant potential using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) radicals and antiarthritic activity against Complete Freund Adjuvant (CFA) induced arthritis. To probe into the causal mechanism of action, NFκB suppressing activity in paraventricular nucleus (PVN) of hypothalamus using potent extract was also studied. Polyphenol rich extract supplementation significantly normalizes the altered blood parameters and reverses the increase in paw thickness, a sign of arthritis in rats. Further, immunohistochemical analysis revealed significant reduction in the NFκB immunoreactive cells in 50% methanolic extract treated (14 days) arthritic rats (57%; p<0.001) as compared to control. These results consolidate the observation, that inhibition of NFκB may be a beneficial approach in the treatment of arthritis. This study corroborates the traditional use of S. grandiflora plant in rheumatism.

Indirect Suppression of Pulsatile LH Secretion by CRH Neurons in the Female Mouse.

Acute stress is a potent suppressor of pulsatile luteinizing hormone (LH) secretion, but the mechanisms through which corticotrophin-releasing hormone (CRH) neurons inhibit gonadotropin-releasing hormone (GnRH) release remain unclear. The activation of paraventricular nucleus (PVN) CRH neurons with Cre-dependent hM3Dq in Crh-Cre female mice resulted in the robust suppression of pulsatile LH secretion. Channelrhodopsin (ChR2)-assisted circuit mapping revealed that PVN CRH neuron projections existed around kisspeptin neurons in the arcuate nucleus (ARN) although many more fibers made close appositions with GnRH neuron distal dendrons in the ventral ARN. Acutely prepared brain slice electrophysiology experiments in GnRH- green fluorescent protein (GFP) mice showed a dose-dependent (30 and 300 nM CRH) activation of firing in ~20% of GnRH neurons in both intact diestrus and ovariectomized mice with inhibitory effects being uncommon (<8%). Confocal GCaMP6 imaging of GnRH neuron distal dendrons in acute para-horizontal brain slices from GnRH-Cre mice injected with Cre-dependent GCaMP6s adeno-associated viruses demonstrated no effects of 30 to 300 nM CRH on GnRH neuron dendron calcium concentrations. Electrophysiological recordings of ARN kisspeptin neurons in Crh-Cre,Kiss1-GFP mice revealed no effects of 30 -300 nM CRH on basal or neurokinin B-stimulated firing rate. Similarly, the optogenetic activation (2-20 Hz) of CRH nerve terminals in the ARN of Crh-Cre,Kiss1-GFP mice injected with Cre-dependent ChR2 had no effect on kisspeptin neuron firing. Together, these studies demonstrate that PVN CRH neurons potently suppress LH pulsatility but do not exert direct inhibitory control over GnRH neurons, at their cell body or dendron, or the ARN kisspeptin neuron pulse generator in the female mouse.

Chronic Stress Induces Persistent Hypertension and Increases NMDA Receptor Activity in the Paraventricular Nucleus in Borderline Hypertensive Rats

Stress activates sympathetic outflow and promotes hypertension development in humans with genetic predisposition. The enhanced N‐methyl‐D‐aspartate receptor (NMDAR) activity in the hypothalamus paraventricular nucleus (PVN) plays a critical role in controlling sympathetic output in hypertension. However, it is unclear how chronic stress affects NMDAR activity in the PVN in borderline hypertensive rats (BHR). BHR are the F1 male offspring from crossing female spontaneously hypertensive rats with male Wistars Kyoto rats (WKY). Arterial blood pressure (ABP) was monitored in free moving rats by using radiotelemetry. Using a 6‐week chronic unpredictable stress protocol, we found that stressed WKY rats had increased ABP during chronic stress but ABP returned to the normal level within a few days after stress. However, the stressed BHR showed a greater increase in ABP during stress and the elevated ABP was sustained for at least 2 weeks after discontinuing stress. Furthermore, whole‐cell voltage clamp recording in brain slices showed that the amplitude of evoked‐NMDAR currents in spinally projecting PVN neurons was significantly higher in stressed BHR than in non‐stressed BHR controls. Inhibiting α2δ‐1 with gabapentin normalized the increased synaptic NMDAR activity of spinally projecting PVN neurons in stressed BHR. In addition, the expression level of GluN1 and α2δ‐1 in the PVN was significantly greater in stressed BHR than in stressed WKY or non‐stressed BHR. These results suggest that chronic stress induces persistent hypertension in BHR, which is associated with α2δ‐1‐mediated NMDAR hyperactivity in PVN presympathetic neurons.Support or Funding InformationAcknowledgmentsSupported by NIH grants HL131161 and HL142133.

Functional Implications of Tyrosine Hydroxylase Immunoreactivity in Rat Brain

Hypothalamo‐pituitary‐adrenal axis is involved in the stress regulation. Understanding the cellular mechanisms involved in this system is critical in studying stress response. Tyrosine hydroxylase (TH), the rate‐limiting enzyme of catecholamine synthesis, has been suggested to play a pivotal role in regulating the neuronal functions under stress. Previous findings showed the brainstem ascending TH‐immunoreactive fibers participate in the cellular activation of paraventricular nucleus of the hypothalamus in response to neurogenic stress. Current study aimed to study the role of TH in regulating brain areas which are involved in the neural circuits in stress response. Immunocytochemical staining of TH confirmed the TH‐immunoreactive positive neurons are found in the locus coeruleus, ventral lateral medulla, nucleus of the solitary tract and zona incerta; wihile TH‐ir fibers are widely found in the forebrain region including the striatum, paraventricular nucleus of hypothalamus, and amygdala. These are areas rich in neurons bearing dopamine receptor, corticotropin‐releasing factor and oxytocin. Using double immunohistochemical staining, we are able to demonstrate the functional significance of tyrosine hydroxylase inputs to these different populations of neurons.Support or Funding InformationWe are grateful to Oregon Tech for supporting undergraduate research as well as Dr. Paul Sawchenko for his generosity in donating rat brain tissues.

Microbial Derived Short Chain Fatty‐Acids and Autonomic Regulation of Cardiovascular Function

Elevated sympathetic outflow is an important contributor to the salt‐sensitive hypertension (SSH). It’s been established that the paraventricular nucleus (PVN) of the hypothalamus regulates autonomic control of cardiovascular function, and increased PVN activity contributes to the elevated sympathetic nerve activity (SNA) in SSH. Accumulating evidence indicates a correlation between gut microbial composition and hypertension. Interestingly, data also suggests there is an increased neural communication between the gastrointestinal (GI) tract and PVN neurons in hypertensive animals. Moreover, it’s been reported high salt diet significantly increased the production of short chain fatty‐acids (SCFAs), microbiota‐derived metabolites. We have shown microinjection of acetate, a SCFA, into the central nucleus of amygdala, significantly increased SNA and arterial blood pressure (ABP). The objective is to determine the role of microbiota‐produced SCFAs, acetate and lactate in the PVN, in regulating SNA and ABP. In anesthetized rats, microinjection with acetate or lactate (0.2 μmol/100nl, n=3~4) into the PVN produced significant increases in splanchnic SNA and ABP (p &lt;0.05~0.01), respectively. Also, pre‐treatment of kynurenic acid (KYN, 7.2 nmole/100 nl), an ionotropic EAA receptor antagonist, significantly (p &lt;0.05) attenuated the sympathoexcitatory responses evoked by either acetate or lactate. These data suggested that activation of glutamate receptors in the PVN contribute to sympathoexcitatory and pressor responses elicited by SCFAs.Alterations microbiota communities’ impact human host physiology and pathophysiology but a clear cause/effect relationship has yet to be established. Often researchers use fecal matter to determine a subject microbiome profile to make health inferences. While the mucosa associated bacterial communities may be more informative regarding the impact on the host, little investigation into differences between fecal and mucosal bacterial communities has occurred. Gathering information about the microbiome from feces and making inferences to the host’s health may not be an optimal method. Our next aim is to test the hypothesis that shifts in mucosa associated bacteria induce changes in SCFAs concentrations in circulation which may underlie the neural mechanisms of increased sympathetic outflow in hypertension. We extracted feces and mucosa tissue from the small intestine (SI), the location within the GI where absorption occurs. Bacterial composition was determined using 16S rRNA sequencing. Analysis of rat mucosal tissue from the SI (n=6) and feces (n=6) confirmed the bacterial community composition was significantly different (p =5.4×10−5) between the two locations. Collectively, this data supports the continuation into the investigation of mucosa bacteria‐derived SCFA involvement in the increase in sympathetic outflow and SSH.Support or Funding InformationSonger Research Award, Jessica R. Bruning, MTU Potage Health Foundation, Qing‐Hui Chen).

Dopaminergic afferents from midbrain to dorsolateral bed nucleus of stria terminalis inhibit release and expression of corticotropin-releasing hormone in paraventricular nucleus.

Dopaminergic (DAergic) neurons of the midbrain ventral tegmental area (VTA) are known to regulate the hypothalamic-pituitary-adrenal (HPA) axis but have no direct projections to the paraventricular nucleus (PVN) of the hypothalamus. This study investigated whether VTA DAergic afferents modulate glutamatergic transmission-dependent GABAergic neurons in dorsolateral bed nucleus of stria terminalis (dlBNST) to affect the activity of the HPA-axis. Herein, we demonstrate that systemic administration of the neurotoxicant 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or the VTA-injection of 1-methyl-4-phenylpyridinium ion (MPP+) in male mice (MPTP-mice and MPP+mice) caused a decline of tyrosine hydroxylase positive (TH+) cells in VTA with a reduction in TH+fibers in the dlBNST. MPTP-mice and MPP+mice displayed a clear increase in serum levels of corticosterone (CORT) and adrenocorticotropic hormone, corticotropin-releasing hormone (CRH) expression, and CRH neuron activity in PVN. The presynaptic glutamate release, glutamatergic synaptic transmission and induction of long-term potentiation in dlBNST of MPTP-mice were suppressed, and these effects were rescued by a D1-like DAergic receptor (D1R) agonist and mimicked in control dlBNST by blockade of D1R. MPTP-mice exhibited low expression of glutamic acid decarboxylase and dysfunction of the excitatory-dependent GABAergic circuit in dlBNST, and these effects were recovered by the administration of D1R agonist. Furthermore, either dlBNST-injection of D1R agonist or PVN-injection of GABAA receptor (GABAA R) agonist could correct the increased secretion and expression of CRH in MPTP-mice. The results indicate that the DAergic afferents from VTA enhance excitatory-dependent activation of GABAergic neurons in dlBNST, which suppress the activity of the HPA-axis.

Oxytocin receptor gene loss influences expression of the oxytocin gene in C57BL/6J mice in a sex‐ and age‐dependent manner

Parental care and sensory stimulation are critical environmental factors that influence oxytocin (OXT) and its receptor (OXTR). Because developmental Oxt mRNA expression is enhanced by sensory-rich early life experience and reduced by sensory deprivation, we predicted that compared to wild-type (WT) littermates, mice with congenital loss of OXTR (OXTR KO), as a genetically induced deprivation, would show impaired Oxt mRNA expression in the offspring hypothalamus during development. Oxt mRNA levels of male and female OXTR KO mice were not different from WT littermates from postnatal day (P)0 to P6, although, by P8, OXTR KO showed significantly decreased Oxt mRNA expression in the hypothalamus compared to WT littermates. At P14, male and female OXTR KO mice had significantly decreased Oxt mRNA expression specifically in the paraventricular nucleus (PVN), but not the supraoptic nucleus (SON), compared to WT littermates. We investigated whether this effect persisted in adulthood (P90) and found a significant genotype by sex interaction where male OXTR KO mice displayed a reduction in Oxt expression specific to the PVN compared to male WT littermates. By contrast, male and female OXTR KO adults had increased Oxt mRNA levels in the SON. These findings suggest that OXTR plays a role in developmental Oxt mRNA expression with sex by genotype interactions apparent at adulthood. We then measured OXT and neural activation in the PVN and SON at P14. We observed more OXT-immunoreactive cells in the PVN of OXTR KO mice but significantly fewer c-Fos immunoreactive cells. There were no genotype differences in immunoreactivity for OXT and no c-Fos activity in the SON at P14. Combined, these data suggest that OXTR WT P14 mice have more PVN activity and are more likely to release OXT than OXTR KO mice. Future experiments are warranted to understand which OXTR-expressing neural circuits modulate the development of the PVN oxytocin system.

Targeting Hypertension: Superoxide Anions are Involved in Apelininduced Long-term High Blood Pressure and Sympathetic Activity in the Paraventricular Nucleus.

To determine whether apelin in paraventricular nucleus (PVN) can be a therapeutic target for hypertension. Apelin is a specific endogenous ligand of orphan G protein-coupled receptor APJ. This study was designed to determine how apelin chronically regulates sympathetic nerve activity and blood pressure in PVN of rats. Apelin and APJ antagonist F13A were infused into PVN with osmotic minipumps. The NAD(P)H oxidase activity and superoxide anions levels in PVN of rats were determined by chemiluminescence. Infusion of apelin into PVN of Wistar-Kyoto (WKY) rats induced chronic increases in systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), plasma norepinephrine (NE) level, maximal depressor response to hexamethonium (Hex), NAD(P)H oxidase activity, superoxide anions levels, and Nox4 expression. Infusion of F13A into PVN of spontaneously hypertensive rats (SHRs) caused chronic decreases in SBP, DBP, MAP, plasma NE level, maximal depressor response to Hex, NAD(P)H oxidase activity, and superoxide anions levels. Hex, a sympathetic ganglion blocker, inhibited apelin-induced increases in SBP, DBP and MAP. SOD overexpression in PVN of SHRs inhibited the apelin-induced increase in SBP, DBP, MAP, plasma NE level, and maximal depressor response to Hex. PVN Nox4 knockdown also attenuated the apelin-induced increase in SBP, DBP, MAP, plasma NE level, and maximal depressor response to Hex. Chronic injection of F13A into PVN reduced fibrosis of renal artery, thoracic aorta, and heart in SHRs. These results demonstrated that in PVN apelin induced long-term high blood pressure and sympathetic activity via increasing oxidative stress.

Abstract 307: Chemogenetic Activation of Paraventricular Oxytocin Neurons Reduces Cardiac Dysfunction During Heart Failure

There is a distinctive cardiac autonomic imbalance in HF consisting of increased sympathetic activity and decreased parasympathetic tone. Recent work has indicated that activation of paraventricular nucleus (PVN) oxytocin neurons increases co-release of oxytocin with glutamate to elevate cardiac vagal tone yet little is known regarding the long-term (16 week) benefit. We hypothesize that activation of oxytocin neurons in the PVN will blunt the progression of HF by reducing inflammation and fibrosis at 16 weeks post-HF initiation than in untreated counterparts. Rats underwent trans-ascending aortic constriction (TAC) to induce HF. In a subset of HF rats (TAC+OXT), oxytocin neurons were activated by excitatory designer receptors exclusively activated by designer drugs (DREADDs). Rats were implanted with ECG telemetry devices and underwent a treadmill protocol to measure peak effort capacity and heart rate recovery (HRR). Cardiac structural measurements were obtained using echocardiography. After 16 weeks, hearts were rapidly excised, Langendorff perfused to measure mechanical function, and prepared for histology and western blot analysis. Indices of cardiac function (stroke volume, ejection fraction, cardiac output, and fractional shortening) indicated preserved function in TAC+OXT compared to TAC. HRR after peak effort capacity values were lowest in TAC and were significantly greater in TAC+OXT (p≤0.05), indicating preservation of cardiac parasympathetic tone. LV developed pressure was significantly impaired in TAC compared to sham as well as significantly improved in TAC+OXT compared to TAC (p≤0.05). Contractility and relaxation were significantly impaired in TAC compared to sham (p≤0.05), while TAC+OXT animals had values not different from sham. TAC animals had collagen III levels 5X higher than TAC+OXT. Histological analysis indicated increased fibrosis in disease groups compared to sham. TAC+OXT had IL-1β levels significantly lower than TAC (p≤0.05). PVN oxytocin neuron activation slows the decline of cardiac function in 16 week post- TAC rats, likely by reinstating cardioprotective parasympathetic activity. This novel method has translational potential since intranasal oxytocin administration has been used in the clinic.