Arginine Vasopressin Expression Research Articles

The Effects of Alcohol Intoxication and Withdrawal on Hypothalamic Neurohormones and Extrahypothalamic Neurotransmitters.

The aim of the present study was to determine the effects of alcohol intoxication and withdrawal on hypothalamic neurohormones such as corticotropin-releasing factor (CRF) and arginine vasopressin (AVP), and extrahypothalamic neurotransmitters such as striatal dopamine (DA), amygdalar gamma aminobutyric acid (GABA), and hippocampal glutamate (GLU). In addition, the participation of the two CRF receptors, CRF1 and CRF2, was investigated. For this purpose, male Wistar rats were exposed to repeated intraperitoneal (ip) administration of alcohol every 12 h, for 4 days and then for 1 day of alcohol abstinence. On the fifth or sixth day, intracerebroventricular (icv) administration of selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B was performed. After 30 min, the expression and concentration of hypothalamic CRF and AVP, the concentration of plasma adrenocorticotropic hormone (ACTH) and corticosterone (CORT), and the release of striatal DA, amygdalar GABA, and hippocampal GLU were measured. Our results indicate that the neuroendocrine changes induced by alcohol intoxication and withdrawal are mediated by CRF1, not CRF2, except for the changes in hypothalamic AVP, which are not mediated by CRF receptors.

Response to endoplasmic reticulum stress in arginine vasopressin neurons.

Arginine vasopressin (AVP) is an antidiuretic hormone synthesized principally in the hypothalamic supraoptic and paraventricular nuclei. The immunoglobulin heavy chain binding protein (BiP), one of the most abundant endoplasmic reticulum (ER) chaperones, is highly expressed in AVP neurons, even under basal conditions. Moreover, its expression is upregulated in proportion to the increase in AVP expression under dehydration. These data suggest that AVP neurons are constantly exposed to ER stress. BiP knockdown in AVP neurons induces ER stress and autophagy, resulting in AVP neuronal loss, indicating that BiP is pivotal in maintaining the AVP neuron system. Furthermore, inhibition of autophagy after BiP knockdown exacerbates AVP neuronal loss, suggesting that autophagy induced under ER stress is a protective cellular mechanism by which AVP neurons cope with ER stress. Familial neurohypophysial diabetes insipidus (FNDI) is an autosomal dominant disorder caused by mutations in the AVP gene. It is characterized by delayed-onset progressive polyuria and eventual AVP neuronal loss. In AVP neurons of FNDI model mice, mutant protein aggregates are confined to a specific compartment of the ER, called the ER-associated compartment (ERAC). The formation of ERACs contributes to maintaining the function of the remaining intact ER, and mutant protein aggregates in ERACs undergo autophagic-lysosomal degradation without isolation or translocation from the ER, representing a novel protein degradation system in the ER.

Adolescence Predatory Risk Alters Social Behaviors and Cognitive Ability and Central Oxytocin and Vasopressin Expression in Adult Brandt’s Voles

Introduction: Stress during adolescence causes long-term behavioral changes in adulthood. We previously found that adolescent exposure to predatory risk augments adolescent social contact and adult parental behavior in Brandt’s voles (Lasiopodomys brandtii). Methods: Here, we determined whether this experience alters sexual behavior, pair-bond formation, and recognition ability as well as basal HPA axis activity, central oxytocin (OT), and arginine-vasopressin (AVP) expression in adulthood. Results: In the social interaction test, repeated cat odor (CO) exposure enhanced the frequency of lordosis by female voles toward an unfamiliar opposite-sex conspecific. CO voles preferred to engage with their partners after 48-h cohabitation whereas the control groups did not, which may reflect stable pair bonds in the CO treatment group. Furthermore, adolescent exposure to CO inhibited novel object recognition and place recognition ability, while it influenced social recognition only among adult males. No effect of adolescent CO exposure was observed for basal HPA axis activity, showing a habituation effect. Finally, we found that CO exposure increased OT and decreased AVP expression in the hypothalamus, including the paraventricular nucleus and anterior hypothalamus. The levels of OT in the medial amygdala were lower, and AVP in the lateral septum was higher in CO voles compared with the control. Conclusion: These findings demonstrate that adolescent exposure to predator risk promotes adult reproductive behavior of Brandt’s voles. Deficits in recognition ability may necessitate alterations in reproductive strategies to enhance inclusive fitness. OT and AVP systems may play a modulatory role in the alteration of social behaviors elicited by adolescent predatory risk.

Early-life maternal deprivation affects the mother-offspring relationship in domestic pigs, as well as the neuroendocrine development and coping behavior of piglets.

Early-life adversity may have programming effects on the psychological and physiological development of offspring. Domestic pigs (Sus scrofa) are an excellent model species for studying these effects because of their many physiological similarities to humans. Piglets from 10 sows were subjected to daily 2-h maternal deprivation on postnatal days (PND) 2–15 alone (DA) or in a group of littermates (DG). Control piglets (C) from 10 sows stayed with their mothers. Mother-offspring interaction, milk oxytocin, and cortisol were analyzed. An open-field/novel-object (OF/NO) test was performed with piglets on PNDs 16 and 40. Plasma cortisol and immune parameters were determined on PND 5 and 16. Two piglets from each group and sow were sacrificed on PND 20 and stress-related gene expression in the limbic system and prefrontal cortex (PFC), as well as splenic lymphocyte proliferative abilities, were examined. The milk cortisol of sows increased during the first separation of mother and offspring on the second day of lactation, whereas milk oxytocin did not change. The increase in cortisol by the OF/NO test on PND 16 was greater in C piglets than in DA and DG ones. DA piglets showed less agitated behavior than DG and C piglets in the OF/NO test at PND 16, but appeared more fearful. On PND 40, DA piglets showed more arousal than DG and C piglets in the OF/NO test. Neither plasma IgA nor N/L ratios in blood nor mitogen-induced proliferation of spleen lymphocytes were affected by deprivation. We found a higher mRNA expression of CRHR1 in the hypothalamus and a higher expression of MR in the hippocampus in DA piglets than in DG ones. The expression of GR, MR, and CRHR1 genes in the PFC was reduced by maternal deprivation, however, the expression of arginine vasopressin and oxytocin receptors was not affected. Repeated maternal deprivation induces sustained effects on stress reactivity and behavior of domestic piglets. Some of these effects were buffered by the presence of littermates. In addition, we found sex-specific differences in behavior and gene expression.

Dex modulates the balance of water-electrolyte metabolism by depressing the expression of AVP in PVN.

Dexmedetomidine (Dex) is a highly selective α2 adrenergic agonist used in clinical anesthesia. Studies have shown that Dex can act on the collecting duct and reduce the body’s water reabsorption, thereby increasing water discharge. However, the specific mechanism of Dex on water homeostasis remains unclear. The hypothalamus is the regulatory center of water and salt balance and secretes related neurochemical hormones, such as arginine vasopressin (AVP), to regulate the discharge of water and salt. The paraventricular nucleus (PVN) and supraoptic nucleus (SON) in the hypothalamus are also considered to be the key targets of the thirst loop. They are responsible for the secretion of AVP. The suprachiasmatic nucleus (SCN) is also one of the brain regions where AVP neurons are densely distributed in the hypothalamus. This study used C57BL/6J mice for behavior, immunofluorescence, and blood analysis experiments. Our results showed that Dex could not only depress the expression of AVP in the PVN but also reduce serum AVP concentration. The animal water intake was decreased without impairing the difference in food consumption and the urine excretion was enhanced after the intraperitoneal injection of Dex, while AVP supplementation restored the water intake and inhibited the urine excretion of mice in the Dex group. In addition, the renin-angiotensin-aldosterone system is vital to maintaining serum sodium concentration and extracellular volume. We found that serum sodium, serum chloride, serum aldosterone (ALD) concentration, and plasma osmolality were decreased in the Dex group, which inhibited water reabsorption, and the plasma osmolarity of mice in the Dex group supplemented with AVP was significantly higher than that in Dex group. We also found that Dex significantly increased the concentration of blood urea nitrogen and decreased the concentration of creatinine within the normal range of clinical indicators, indicating that there was no substantive lesion in the renal parenchyma. These results showed that Dex could modulate the balance of water-electrolyte metabolism by depressing the expression of AVP in PVN without impairing renal function.

Upregulation of the hypothalamo-neurohypophysial system and activation of vasopressin neurones attenuates hyperalgesia in a neuropathic pain model rat

Arginine vasopressin (AVP) is a hypothalamic neurosecretory hormone well known as an antidiuretic, and recently reported to be involved in pain modulation. The expression kinetics of AVP and its potential involvement in the descending pain modulation system (DPMS) in neuropathic pain (NP) remains unclear. We investigated AVP expression and its effects on mechanical and thermal nociceptive thresholds using a unilateral spinal nerve ligation (SNL) model. All rats with SNL developed NP. Intensities of enhanced green fluorescent protein (eGFP) in the supraoptic and paraventricular nuclei, median eminence, and posterior pituitary were significantly increased at 7 and 14 days post-SNL in AVP-eGFP rats. In situ hybridisation histochemistry revealed significantly increased AVP mRNA expression at 14 days post-SNL compared with the sham control group. The chemogenetic activation of AVP neurones significantly attenuated mechanical and thermal hyperalgesia with elevated plasma AVP concentration. These analgesic effects were suppressed by pre-administration with V1a receptor antagonist. AVP neurones increased the neuronal activity of serotonergic dorsal raphe, noradrenergic locus coeruleus, and inhibitory interneurones in the spinal dorsal horn. These results suggest that the hypothalamo-neurohypophysial system of AVP is upregulated in NP and activated endogenous AVP exerts analgesic effects via the V1a receptors. AVP neurones may activate the DPMS.

Knockdown of sexually differentiated vasopressin expression in the bed nucleus of the stria terminalis reduces social and sexual behaviour in male, but not female, mice.

The neuropeptide arginine-vasopressin (AVP) has long been implicated in the regulation of social behaviour and communication, but the sources of AVP release relevant for behaviour have not been precisely determined. Ablations of the sexually dimorphic AVP cells within the bed nucleus of the stria terminalis (BNST), which are more numerous in males, affect social behaviour differently in males and females. However, it is unknown whether these behavioural effects are caused by a reduction of AVP or of other factors associated with these cells. To test the role of AVP specifically, we used an shRNA viral construct to knock down AVP gene expression within the BNST of wild-type male and female mice, using scrambled sequence virus as a control, and evaluated subsequent changes in social behaviours (social investigation, ultrasonic vocalization (USV), scent marking, copulation, and aggression), or anxiety-like behaviours (elevated plus maze). We observed that, in males, knockdown of AVP expression in the BNST strongly reduced investigation of novel males, aggressive signalling towards other males (tail rattling, USV), and copulatory behaviour, but did not alter attack initiation, other measures of social communication, or anxiety-like behaviours. In females, however, BNST AVP knockdown did not alter any of these behaviours. These results point to differential involvement of AVP derived from the BNST in social behaviour.

Population variation alters aggression-associated oxytocin and vasopressin expressions in brains of Brandt\u2019s voles in field conditions

Density-dependent change in aggressive behavior contributes to the population regulation of many small rodents, but the underlying neurological mechanisms have not been examined in field conditions. We hypothesized that crowding stress and aggression-associated oxytocin (OT) and arginine vasopressin (AVP) in specific regions of the brain may be closely related to aggressive behaviors and population changes of small rodents. We analyzed the association of OT and AVP expression, aggressive behavior, and population density of Brandt’s voles in 24 large semi-natural enclosures (0.48 ha each) in Inner Mongolia grassland. We tested the effects of population density on the OT/AVP system and aggressive behavior by experimentally manipulating populations of Brandt’s voles in the grassland enclosures. High density was positively and significantly associated with more aggressive behavior, and increased expression of mRNA and protein of AVP and its receptor, but decreased expression of mRNA and protein of OT and its receptor in specific brain regions of the voles. Our study suggests that changes in OT/AVP expression are likely a result of the increased psychosocial stress that these voles experience during overcrowding, and thus the OT/AVP system can be used as indicators of density-dependent stressors in Brandt’s voles.

Doublecortin-like expressing astrocytes of the suprachiasmatic nucleus are implicated in the biosynthesis of vasopressin and influences circadian rhythms.

We have recently identified a novel plasticity protein, doublecortin‐like (DCL), that is specifically expressed in the shell of the mouse suprachiasmatic nucleus (SCN). DCL is implicated in neuroplastic events, such as neurogenesis, that require structural rearrangements of the microtubule cytoskeleton, enabling dynamic movements of cell bodies and dendrites. We have inspected DCL expression in the SCN by confocal microscopy and found that DCL is expressed in GABA transporter‐3 (GAT3)‐positive astrocytes that envelope arginine vasopressin (AVP)‐expressing cells. To investigate the role of these DCL‐positive astrocytes in circadian rhythmicity, we have used transgenic mice expressing doxycycline‐induced short‐hairpin (sh) RNA's targeting DCL mRNA (DCL knockdown mice). Compared with littermate wild type (WT) controls, DCL‐knockdown mice exhibit significant shorter circadian rest‐activity periods in constant darkness and adjusted significantly faster to a jet‐lag protocol. As DCL‐positive astrocytes are closely associated with AVP‐positive cells, we analyzed AVP expression in DCL‐knockdown mice and in their WT littermates by 3D reconstructions and transmission electron microscopy (TEM). We found significantly higher numbers of AVP‐positive cells with increased volume and more intensity in DCL‐knockdown mice. We found alterations in the numbers of dense core vesicle‐containing neurons at ZT8 and ZT20 suggesting that the peak and trough of neuropeptide biosynthesis is dampened in DCL‐knockdown mice compared to WT littermates. Together, our data suggest an important role for the astrocytic plasticity in the regulation of circadian rhythms and point to the existence of a specific DCL+ astrocyte‐AVP+ neuronal network located in the dorsal SCN implicated in AVP biosynthesis.

Temporal Profiling of Molecular Alterations in the Hypothalamic Paraventricular Nucleus During Angiotensin‐II Hypertension

The hypothalamic paraventricular nucleus (PVN) plays a central role in cardiovascular regulation including hypertension development in response to elevations in angiotensin-II (Ang-II). Upstream circumventricular nuclei located outside of the blood-brain-barrier sense circulating Ang-II and influence PVN endocrine and autonomic regulation via efferent synaptic projections. Despite progress in unraveling the function of circumventricular-PVN networks in neurogenic hypertension development, the underlying PVN mechanisms responsible for hypertension development remain unclear. In particular, most investigations have examined PVN alterations during established hypertension, which limits insight into molecular changes that may occur prior to hypertension development. Based on this, we performed a detailed temporal profiling of key molecular targets in the PVN during Ang-II hypertension progression. Male C57Bl/6J mice were implanted with subcutaneous osmotic minipumps for chronic delivery of low dose Ang-II (600 ng/kg/min). Brains were harvested for immunohistochemistry analysis of target molecules across rostral to caudal subregions of the PVN (n=3-4/group) at baseline (day 0), pre-hypertensive (days 3 and 7), and established-hypertension (day 14) timepoints. Previous work has suggested a role for arginine vasopressin (AVP) in Ang-II-induced hypertension. In line with this, AVP immunoreactivity in the PVN was elevated within 3 days of Ang-II infusion; this was evident only in the caudal PVN (day 3 fold change: 2.5±0.2, density/cell, p<0.05), whereas AVP expression in the rostral and medial portions was unchanged. Interestingly, caudal AVP immunoreactivity returned to basal levels by day 7 and remained low for the remainder of the protocol. In contrast to AVP, oxytocin expression was unchanged across the rostral to caudal PVN during 2-week Ang-II hypertension development. We also measured preproenkephalin (PPE) immunoreactivity, and found a progressive increase throughout the entire PVN with elevations initiated at pre-hypertensive times (day 7 fold change: 2.0±0.1, density/area, p=0.08) that were sustained during established hypertension (day 14 fold change: 2.6±0.3, density/area, p<0.05). To test possible involvement of the arcuate nucleus, which transmits circulating information from the median eminence to the PVN, in Ang-II hypertension, we measured alpha-melanocortin stimulating hormone (alpha-MSH) levels. Histological analysis for alpha-MSH immunoreactivity in the PVN, as an indicator of synaptic innervation strength from arcuate nucleus proopiomelanocortin neurons, revealed no changes during Ang-II infusion. Collectively, these findings indicate elevations in PVN AVP and PPE, but not oxytocin and alpha-MSH, in response to elevations in circulating Ang-II. Furthermore, the temporal responses suggest that different PVN molecules may be responsible for the initiation (e.g. AVP) versus maintenance (e.g. PPE) of Ang-II hypertension.

Arginine vasopressin-Venus reporter mice as a tool for studying magnocellular arginine vasopressin neurons

Arginine vasopressin (AVP) synthesized in the magnocellular neurons of the hypothalamus is transported through their axons and released from the posterior pituitary into the systemic circulation to act as an antidiuretic hormone. AVP synthesis and release are precisely regulated by changes in plasma osmolality. Magnocellular AVP neurons receive innervation from osmosensory and sodium-sensing neurons, but previous studies showed that AVP neurons per se are osmosensitive as well. In the current study, we made AVP-Venus reporter mice and showed that Venus was expressed exclusively in AVP neurons and was upregulated under water deprivation. In hypothalamic organotypic cultures from the AVP-Venus mice, Venus-labeled AVP neurons in the supraoptic and paraventricular nuclei survived for 1 month, and Venus expression was upregulated by forskolin. Furthermore, in dissociated Venus-labeled magnocellular neurons, treatment with NaCl, but not with mannitol, decreased Venus fluorescence in the soma of the AVP neurons. Thus, Venus expression in AVP-Venus transgenic mice, as well as in primary cultures, faithfully showed the properties of intrinsic AVP expression. These findings indicate that AVP-Venus mice as well as the primary hypothalamic cultures could be useful for studying magnocellular AVP neurons.

Endoplasmic reticulum chaperone BiP/GRP78 knockdown leads to autophagy and cell death of arginine vasopressin neurons in mice

The immunoglobulin heavy chain binding protein (BiP), also referred to as 78-kDa glucose-regulated protein (GRP78), is a pivotal endoplasmic reticulum (ER) chaperone which modulates the unfolded protein response under ER stress. Our previous studies showed that BiP is expressed in arginine vasopressin (AVP) neurons under non-stress conditions and that BiP expression is upregulated in proportion to the increased AVP expression under dehydration. To clarify the role of BiP in AVP neurons, we used a viral approach in combination with shRNA interference for BiP knockdown in mouse AVP neurons. Injection of a recombinant adeno-associated virus equipped with a mouse AVP promoter and BiP shRNA cassette provided specific BiP knockdown in AVP neurons of the supraoptic (SON) and paraventricular nuclei (PVN) in mice. AVP neuron-specific BiP knockdown led to ER stress and AVP neuronal loss in the SON and PVN, resulting in increased urine volume due to lack of AVP secretion. Immunoelectron microscopy of AVP neurons revealed that autophagy was activated through the process of AVP neuronal loss, whereas no obvious features characteristic of apoptosis were observed. Pharmacological inhibition of autophagy by chloroquine exacerbated the AVP neuronal loss due to BiP knockdown, indicating a protective role of autophagy in AVP neurons under ER stress. In summary, our results demonstrate that BiP is essential for the AVP neuron system.

Regulation and role of arginine vasopressin in myocardial infarction/reperfusion

Abstract Background Little attention is paid to the coronary microvasculature when treating acute myocardial infarction (MI). Microvascular obstruction contributes to ischaemia-reperfusion (I-R) injury. One proposed mechanism is a persistent vasoconstrictor tone during MI/reperfusion. Arginine vasopressin (AVP) has a vasoactive effect on the coronary microvessels. Moreover, cardiac AVP synthesis was found in an animal model. To exert vasoconstriction, AVP binds to its receptor 1a (AVPR1a). Aims (i) To analyse the AVP levels during MI/reperfusion (ii) To assess cardiac AVP and AVPR1a expressions in MI/reperfusion mouse models. Methods We took arterial blood samples from ST elevation MI (STEMI) patients admitted to our hospital over the course of MI/reperfusion for AVP levels quantification. We also measured AVP through its more stable surrogate biomarker, copeptin. Cardiac MRI was done to evaluate coronary microvasculature, infarct size, and left ventricular ejection fraction (LVEF) 1 week post-admission. Cardiac AVP and AVPR1a expressions were assessed by polymerase chain reaction (PCR) in mouse models. Results STEMI patients displayed bothAVPand copeptinlevels elevation at baseline (130.8±20.5 pmol/l, n=23) until 90 min post-reperfusion (55.7±6.2 pmol/l, n=23). Their concentrations began to approach normal levels at 24h. Patients with poorer reperfusion outcomes had copeptin concentrations that remained above normal level after 24h following reperfusion. Copeptin levels at 24h post-reperfusion were significantly higher in patients who developed larger infarct size (p=0.004) and lower LVEF (p=0.009). Patients with microvascular obstruction tended to have higher copeptin levels from admission until 24h post-reperfusion. Mouse models showed no cardiac AVP expression but significantly high AVPR1a expression at 2h post-reperfusion. Conclusion In STEMI patients, circulating AVP level is elevated over the course of MI/reperfusion. In MI/reperfusion mouse models, cardiac AVP synthesis is absent but cardiac AVPR1a is upregulated. The combination of delayed decline in AVP concentrations and AVPR1a upregulation may increase the possibility for AVP to mediate I-R injury through microvascular disturbance. Increased AVP levels at 24h post-reperfusion are significantly associated with poor reperfusion outcome. These results warrant further studies concerning the use of AVP receptor antagonist in STEMI patients undergoing reperfusion therapy Copeptin levels and reperfusion outcomes Funding Acknowledgement Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): Newcastle University MRes Programme

Male-specific features are reduced in Mecp2-null mice: analyses of vasopressinergic innervation, pheromone production and social behaviour.

Deficits in arginine vasopressin (AVP) and oxytocin (OT), two neuropeptides closely implicated in the modulation of social behaviours, have been reported in some early developmental disorders and autism spectrum disorders. Mutations in the X-linked methyl-CpG-binding protein 2 (MECP2) gene are associated to Rett syndrome and other neuropsychiatric conditions. Thus, we first analysed AVP and OT expression in the brain of Mecp2-mutant mice by immunohistochemistry. Our results revealed no significant differences in these systems in young adult Mecp2-heterozygous females, as compared to WT littermates. By contrast, we found a significant reduction in the sexually dimorphic, testosterone-dependent, vasopressinergic innervation in several nuclei of the social brain network and oxytocinergic innervation in the lateral habenula of Mecp2-null males, as compared to WT littermates. Analysis of urinary production of pheromones shows that Mecp2-null males lack the testosterone-dependent pheromone darcin, strongly suggesting low levels of androgens in these males. In addition, resident-intruder tests revealed lack of aggressive behaviour in Mecp2-null males and decreased chemoinvestigation of the intruder. By contrast, Mecp2-null males exhibited enhanced social approach, as compared to WT animals, in a 3-chamber social interaction test. In summary, Mecp2-null males, which display internal testicles, display a significant reduction of some male-specific features, such as vasopressinergic innervation within the social brain network, male pheromone production and aggressive behaviour. Thus, atypical social behaviours in Mecp2-null males may be caused, at least in part, by the effect of lack of MeCP2 over sexual differentiation.

Peripherally administered cisplatin activates a parvocellular neuronal subtype expressing arginine vasopressin and enhanced green fluorescent protein in the paraventricular nucleus of a transgenic rat

Cisplatin is one of the most potent anti-cancer drugs, though several side effects can induce stress responses such as activation of the hypothalamic–pituitary adrenal (HPA) axis. Arginine vasopressin (AVP) and corticotrophin-releasing hormone (CRH) expressed in the parvocellular division of the paraventricular nucleus (pPVN) play an important role in the stress-induced activation of the HPA axis. We aimed to evaluate whether intraperitoneal (i.p.) administration of cisplatin could activate parvocellular neurons in the pPVN, using a transgenic rat model that expresses the fusion gene of AVP and enhanced green fluorescent protein (eGFP). Along with the induction of FosB, a marker of neuronal activation, i.p. administration of cisplatin significantly increased eGFP fluorescent intensities in the pPVN. In situ hybridization histochemistry revealed that AVP-eGFP and CRH mRNAs in the pPVN were increased significantly in cisplatin-treated rats. These results suggest that cisplatin administration increases neuronal activation and upregulates AVP and CRH expression in the pPVN.

Over-expression of arginine vasopressin in magnocellular neurosecretory cells of hypothalamus and its potential relationship with development of diabetic nephropathy

IntroductionWe aimed to assess our hypothesis that the expression changes of arginine vasopressin (AVP) in the magnocellular neurosecretory cells (MNCs) of hypothalamus and V2 receptor for AVP (RVP) in kidney may contribute to the pathogenesis of diabetic nephropathy (DN).Material and methodsTwenty-five male Wistar rats were randomly assigned to the control group and the diabetes mellitus (DM) group. Periodic acid-Schiff (PAS) staining and electron microscopy were used for morphological studies. Immunohistochemical staining for glial fibrillary acidic protein (GFAP) is standard for visualization of reactive astrocytes in the hypothalamus. Hypothalamus was used for immunofluorescence of AVP. Kidney was used for immunohistochemical staining of RVP. Quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) was used for quantitative determinations of AVP mRNA in hypothalamus and RVP mRNA in kidney. Western blot was used to measure the protein expression of AVP in hypothalamus and RVP in kidney.ResultsMorphological studies showed abnormalities in kidney and hypothalamus in the DM group. The number of neurons and the gray value of astrocytes in hypothalamus in the DM group were markedly decreased. The expression level of AVP in hypothalamus and the expression level of RVP in kidney of DM rats were significantly increased. The positive correlations between the proteinuria and expression (mRNA and protein) of AVP, proteinuria and expression (mRNA and protein) of RVP, and the expression of AVP and RVP levels were found.ConclusionsAVP was upregulated in the MNCs of hypothalamus and RVP was upregulated in kidney in streptozotocin-induced DM rats, indicating their potential roles in the development of DN.

Childhood stress impairs social function through AVP-dependent mechanisms

Impaired social function is a core feature of many psychiatric illnesses. Adverse experiences during childhood increase risk for mental illness, however it is currently unclear whether stress early in life plays a direct role in the development of social difficulties. Using a rat model of pre-pubertal stress (PPS), we investigated effects on social behaviour, oxytocin and arginine vasopressin (AVP) in the periphery (plasma) and centrally in the paraventricular and supraoptic hypothalamic nuclei. We also explored social performance and AVP expression (plasma) in participants with borderline personality disorder (BPD) who experienced a high incidence of childhood stress. Social behaviour was impaired and AVP expression increased in animals experiencing PPS and participants with BPD. Behavioural deficits in animals were rescued through administration of the AVPR1a antagonist Relcovaptan (SR49059). AVP levels and recognition of negative emotions were significantly correlated in BPD participants only. In conclusion, early life stress plays a role in the precipitation of social dysfunction, and AVP mediates at least part of this effect.

Effect of Yokukansan and Yokukansankachimpihange on Aggressive Behavior, 5-HT Receptors and Arginine Vasopressin Expression in Social Isolation-Reared Mice.

The traditional herbal medicines yokukansan (YKS) and yokukansankachimpihange (YKSCH) are prescribed for neurosis, insomnia or night crying and irritability in children. YKSCH comprises YKS and two additional herbs, a chimpi and a hange, and is used to treat digestive function deficiencies. However, the differences between the effects of YKS and YKSCH on brain function are unclear. The present study examined the effects of YKS and YKSCH on aggressive behavior in mice reared under a social isolation (SI) condition. Mice were housed individually for 6 weeks. YKS and YKSCH were administered orally for 2 weeks before aggression tests. SI increased aggressive behavior against naïve mice, and YKS, but not YKSCH, significantly attenuated this aggressive behavior. Because serotonin (5-HT)2A and 5-HT3A receptor antagonists are reported to have anti-aggressive effects, the mRNA levels of these receptors were examined. YKS attenuated the SI-induced increase in 5-HT2A and 5-HT3A receptor mRNA in the amygdala. On the other hand, YKSCH attenuated the SI-induced increase in 5-HT1A receptor mRNA. YKS and YKSCH did not affect 5-HT and its metabolite 5-hydroxyindoleacetic acid content in the amygdala. However, YKSCH increased the mRNA level of arginine vasopressin (AVP), which is a neuropeptide that has been implicated in aggression, in the amygdala. These results suggest that YKS ameliorates aggressive behavior by decreasing 5-HT2A and 5-HT3A receptor expression. The YKSCH-induced increase in AVP may disrupt the anti-aggressive effect of YKS. YKS may be more effective than YKSCH for treating irritability if digestive function deficiencies are not considered.

Effects and mechanism of injection of glutamate into hypothalamic paraventricular nucleus on visceral pain in chronic visceral hypersensitivity rats

Objective To investigate the effects of glutamate (Glu) injected into hypothalamic paraventricular nucleus (PVN) on visceral pain of chronic visceral hypersensitivity (CVH) rats and its possible mechanism. Methods Newborn SD rats were given CVH rat model by colorectal distension (CRD) on the 8th, 10th and 12th day after birth. Thirty rats with successful CVH model were randomly divided into CVH model group (CVH group), CVH + injection of saline into PVN group (NS group), CVH+ injection of Glu into PVN (3, 6, and 12 μg Glu, namely G3, G6, and G12, respectively), 6 rats in each group, and 6 SD rats with matching body mass were taken as sham operation group (Sham group). The pain behavior of the rats was evaluated by pain threshold, abdominal withdrawal reflex (AWR) score, and abdominal external oblique muscle electromyography (EMG). The expression of arginine vasopressin (AVP) and the proliferation of colon tissue were detected by immunohistochemical staining. The apoptosis of colon tissue was detected by TUNEL. Results Compared with the NS group, the pain thresholds of the G3, G6 and G12 groups increased, and the AWR scores and EMG amplitudes decreased. The differences were statistically significant(Pain threshold: t=7.65, 16.31, 24.78, both P<0.05; AWR scores: t=-2.98, -4.77, -7.29, both P<0.05; EMG amplitudes: t=-3.06, -5.75, -8.92, both P<0.05). Compared with the Sham group, the expression of AVP in PVN of the CVH group and NS group decreased ((42.63±5.20) %, (18.67±2.94) %, (17.53±2.47) %; t=6.95, t=7.56, both P<0.05). The expression of AVP was increased after different doses of Glu into PVN, and the AVP level in G12 group ((18.15±6.49)%) was higher than that of NS group, the difference was statistically significant (t=-4.21, P<0.05). Compared with the Sham group, the expression of PCNA in colonic mucosal cells of the CVH group and NS group decreased ((65.48±1.68) %, (18.39±1.67) %, (17.69±1.68) %; t=34.35, t=34.80, both P<0.05). The expression of PCNA was increased after different doses of Glu injected into PVN, and the PCNA level in G12 group ((59.91±5.63)%) was higher than that of NS group, the difference was statistically significant (t=-12.44, P<0.05). Compared with the Sham group, the expression of apoptotic cells in colonic mucosal cells of the CVH group and NS group increased ((23.38±11.40)%, (83.79±3.57)%, (80.91±2.47)%; t=-8.77, t=-8.54, both P<0.05). The expression of apoptotic cells was decreased after different doses of Glu into PVN, and the G12 group was ((18.15±6.49) %). Compared with NS group, the difference was statistically significant (t=15.65, P<0.05). Conclusion Injection of Glu into hypothalamic PVN can alleviate the visceral pain behaviors in CVH rats, and its mechanism may be related to arginine vasopressin. Key words: Chronic visceral hypersensitivity; Hypothalamic paraventricular nucleus; Glutamate; Arginine vasopressin; Pain; Rat

Sex Differences in Expression of Methionine Sulfoxide Reductase A in Hypothalamic Paraventricular Nucleus in Rats with Heart Failure after Myocardial Infarction

Myocardial‐infarction (MI)‐induced heart failure (HF) leads to elevated oxidative stress and proinflammatory cytokine (PIC) expression in the brain and arginine vasopressin (AVP) secretion, contributing to sympathetic excitation and the progression of HF. We recently reported that female rats with HF following MI have less PIC and AVP expression in the hypothalamic paraventricular nucleus (PVN), a key cardiovascular‐related center of the brain that regulates sympathetic nerve activity and extracellular fluid volume. Female animals also exhibited less peripheral sympathetic and vasopressinergic activity and less hemodynamic compromise than male HF rats with the same degree of initial ischemic cardiac injury. The mechanisms responsible for these sex differences remain unclear. Emerging evidence reveals that methionine sulfoxide reductase A (MsrA), an intracellular enzyme that reverses protein methionine oxidation, is protective against brain oxidative stress, neuroinflammation and sympathetic excitation. Here we examined whether MsrA is expressed in the cardiovascular‐related centers of the brain and whether MsrA is altered in HF after MI in male and female rats. Male and female SD rats at ~13 weeks of age underwent MI to induce HF and were euthanized for molecular and immunofluorescent studies 4 weeks later. Age‐matched male and female rats served as controls. There were no differences between male and female rats in ischemic zone or left ventricular ejection fraction at 24 hours and at 4 weeks after MI as assessed by echocardiography. mRNA expression of MsrA in the PVN was significantly higher in female than male control rats (2.06 ± 0.25 vs 1.09 ± 0.16, p &lt; 0.05). mRNA expression of MsrA in the PVN was not affected by HF in female rats (2.12 ± 0.46) but was significantly lower (0.43 ± 0.02, p &lt; 0.01) in male HF rats compared with their age‐matched controls. There was no difference in mRNA expression of MsrA in brain cortex among four experimental groups. Confocal imaging revealed MsrA positive immunofluorescence in the neurons of the PVN, mainly in the magnocellular subdivision, in both male control and female control rats. MsrA positive immunofluorescence was also observed in the subfornical organ, another cardiovascular‐related nucleus, and in the cortex in both male control and female control rats. These results indicate that MsrA is expressed in key cardiovascular‐related centers of the brain, and that there are sex differences in the expression of MsrA in the PVN under physiological conditions and in MI‐induced HF. Whether differences in the expression of MsrA in the PVN play a role in the sex differences in the central and peripheral manifestations of MI‐induced HF deserves further investigation.Support or Funding InformationSupported by NIH grants R01HL073986 and R01HL139521This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.