Arginine vasopressin differentially modulates GABAergic synaptic transmission onto temperature-sensitive and temperature-insensitive neurons in the rat preoptic area.

The preoptic area (POA) of the hypothalamus, containing temperature-sensitive and temperature-insensitive neurons, plays a key role in specific thermoregulatory responses. Although arginine vasopressin (AVP) has been shown to induce hypothermia by increasing the firing activities of warm-sensitive neurons and decreasing those of cold-sensitive and temperature-insensitive neurons, the effects of AVP on POA GABAergic transmission remain unknown. Herein, inhibitory postsynaptic currents (IPSCs) of temperature-sensitive and temperature-insensitive neurons in POA slices were recorded using whole-cell patch clamp. By monitoring changes in GABAergic transmission during AVP treatment, we showed that AVP decreased the amplitudes and frequencies of spontaneous IPSCs in mostly warm-sensitive neurons and in some temperature-insensitive neurons but increased these parameters in other temperature-insensitive neurons. The IPSC amplitude was reduced for only cold-sensitive neurons. RT-PCR and Western blot analyses further confirmed the POA expression of V1a receptors and GABAA receptors, including the subunits α1, α2, α3, ß2, ß3 and γ2. The effects of AVP on IPSCs in temperature-sensitive and temperature-insensitive neurons were dependent on G proteins and intracellular Ca2+ . AVP-mediated modulation was associated with changes in the kinetic parameters (decay time, 10-90% rise time, half-width). Together, these results suggest that AVP, acting via V1a receptors but not V1b receptors, differentially modulates GABAergic synaptic transmission and fine-tunes the firing activities of temperature-sensitive and temperature-insensitive neurons in the rat POA.

Detrimental Impact of Vasopressin V2 Receptor Antagonism in a SU5416/Hypoxia/Normoxia-Exposed Rat Model of Pulmonary Arterial Hypertension.

BACKGROUND: The expression of vasopressin type 2 receptor (V2R) in the lung, and the long-term effects of tolvaptan, a selective V2R antagonist, on pulmonary circulation and right ventricular (RV) remodeling in a pulmonary arterial hypertension (PAH) rat model were evaluated. METHODS AND RESULTS: Six-week-old male Sprague-Dawley rats were injected subcutaneously with 20 mg/kg of SU5416 and were exposed to hypoxia for 3 weeks followed by re-exposure to normoxia for 7 weeks. These rats showed signs of RV failure and upregulation of V2R and cAMP in the lung tissue at 10 weeks after SU5416 injection. They were then treated with either 0.05% tolvaptan in diet (SUHx+Tolv) or normal diet (SUHx) during 5-10 weeks of SU5416 injection. Normal control rats (Cont) were also used for comparison. SUHx+Tolv had significantly higher pulmonary arterial pressure, more progressive pulmonary arterial remodeling, and more severe myocyte hypertrophy and interstitial myocardial fibrosis in the right ventricle compared with SUHx despite achieving successful preload reduction. CONCLUSIONS: Chronic vasopressin V2R antagonism may contribute to the worsening of PAH and the development of RV remodeling.

ß-adrenergic receptor-mediated cardiac contractility is inhibited via vasopressin type 1A-receptor-dependent signaling.

BACKGROUND: Enhanced arginine vasopressin levels are associated with increased mortality during end-stage human heart failure, and cardiac arginine vasopressin type 1A receptor (V1AR) expression becomes increased. Additionally, mice with cardiac-restricted V1AR overexpression develop cardiomyopathy and decreased ß-adrenergic receptor (ßAR) responsiveness. This led us to hypothesize that V1AR signaling regulates ßAR responsiveness and in doing so contributes to development of heart failure. METHODS AND RESULTS: Transaortic constriction resulted in decreased cardiac function and ßAR density and increased cardiac V1AR expression, effects reversed by a V1AR-selective antagonist. Molecularly, V1AR stimulation led to decreased ßAR ligand affinity, as well as ßAR-induced Ca(2+) mobilization and cAMP generation in isolated adult cardiomyocytes, effects recapitulated via ex vivo Langendorff analysis. V1AR-mediated regulation of ßAR responsiveness was demonstrated to occur in a previously unrecognized Gq protein-independent/G protein receptor kinase-dependent manner. CONCLUSIONS: This newly discovered relationship between cardiac V1AR and ßAR may be informative for the treatment of patients with acute decompensated heart failure and elevated arginine vasopressin.

Integrin-linked kinase regulates tubular aquaporin-2 content and intracellular location: a link between the extracellular matrix and water reabsorption.

One of the clinical alterations observed in chronic renal disease (CRD) is the impaired urine concentration, known as diabetes insipidus (DI). Tubulointerstitial fibrosis of the kidney is also a pathological finding observed in CRD and involves composition of extracellular matrix (ECM). However, an association between these two events has not been elucidated. In this study, we showed that the extracellular-to-intracellular scaffold protein integrin-linked kinase (ILK) regulates expression of tubular water channel aquaporin-2 (AQP2) and its apical membrane presence in the renal tubule. Basally, polyuria and decreased urine osmolality were present in ILK conditional-knockdown (cKD-ILK) adult mice compared with nondepleted ILK littermates. No changes were observed in arginine-vasopressin (AVP) blood levels, renal receptor (V2R), or AQP3 expression. However, tubular AQP2 was decreased in expression and apical membrane presence in cKD-ILK mice, where the canonical V2R/cAMP axis activation is still functional, but independent of the absence of ILK. Thus, cKD-ILK constitutes a nephrogenic diabetes insipidus (NDI) model. AQP2 and ILK colocalize in cultured inner medullary collecting duct (mIMCD3) cells. Specific ILK siRNAs and collagen I (Col) decrease ILK and AQP2 levels and AQP2 presence on the membrane of tubular mIMCD3 cells, which impairs the capacity of the cells to transport water under hypotonic stress. The present work points to ILK as a therapeutic target in NDI.

[Vascular reactivity and receptor expression of endogenous vasoconstrictor in rats with alcoholic cardiomyopathy and insulation stress].

On the model of alcohol cardiomyopathy studied the effect of chronic ethanol consumption and the insulation stress on the reactivity of isolated rat aorta and the expression of the endogenous vasoconstrictor receptors in the aorta. Pushing alcoholization outbred rats was carried out for 24-28 weeks, using as the sole source of liquid 10% ethanol solution. In assessing the results of the study took into account the age of the animals. It is found that the reactivity of isolated aortic rings dissected from the body of old (40-45 weeks) nonstressed rats in response to endothelin-1 (ET1), noradrenaline (NA), arginine vasopressin (AVP) or angiotensin II (ATII) is not different from such reactivity for young animals. However, with the increase in life expectancy increases the sensitivity of vessels to vasoconstrictor action of serotonin (5HT). Prolonged stress insulation and the consumption of high doses of ethanol the stress lead to increased ET1- and NA-induced contraction of the aortic rings and a significant decrease in contractile response of the aorta to the impact ATII and AVP. Stress and alco- hol in combination with stress causing reduction mRNA ETA-R, AT1A-R. and V1A-R and increased mRNA α1-AR in rat aorta. It is found that in the vessels of stressed and alcoholized animals reduced level of expression of cytosolic glucocorticoid receptors (GR), which is a transcription factor for genes ETA-R, AT1A-R V1A-R. It is propoused that the development of vascular hyporesponsiveness of stressed and alcoholized rats to action ATII and AVP is the result of reducing the expression of their receptors on the GR-dependent mechanism. It is shown that under the influence of ethanol vessels become hyporeactivity selectively with respect to the action of 5HT. The mechanism of this process is unclear. Importantly, the changes in the contractile properties vessels recovered from the rat at 1 month after the abolition of the reception of ethanol (step abstinence) were similar to changes found at the alcohohzed animals. Thus, the importance of breaking the neuroendocrine regulation of vascular tone during long-term consumption of ethanol has a stressor components. Furthermore, in this experimental model we not received data in favor ethanol direct impact on the development of hypertension.

The intercalated cells of the mouse kidney OMCD(is) are the target of the vasopressin V1a receptor axis for urinary acidification.

BACKGROUND: Vasopressin V1a receptor (V1aR) null mice have insufficient acid-base balance, but the target cell for V1aR signaling which results in the urinary acidification has not been identified. METHODS: By using a quantitative in situ hybridization technique and a double-staining technique with an anti-AQP3 antibody in mice, we investigated the axial distribution and acidosis-induced expression of V1aR mRNA along the nephron. We also investigated the acidosis-induced morphological change in the tubule cells from wild-type and V1aR-null (V1aR(-/-)) mice. RESULTS: In the normal condition, V1aR mRNA was moderately expressed in the medullary thick ascending limb (MTAL) and highly expressed in the intercalated cell (IC) throughout the collecting duct (CD). However, no expression was observed in the proximal tubule, thin limbs of Henle's loop, and the principal cell of the CD. Importantly, V1aR mRNA was upregulated significantly both in the TAL and the IC of the CD in the inner stripe of the outer medulla (MTALis and IC of OMCDis, respectively) when mice were treated with NH4Cl (0.28 mol/L) for 6 days. Acidosis-induced hypertrophy, which was completely attenuated in V1aR(-/-) mice, was observed only in the IC of OMCDis (P < 0.005). In addition, urinary excretion of ammonia (NH3/NH4 (+)) was significantly decreased on day 3 (P < 0.05) and day 6 (P < 0.005) in the V1aR(-/-) mice treated with NH4Cl. CONCLUSION: In conclusion, the IC of OMCDis may be the target cell stimulated by the vasopressin V1aR axis and contribute to urinary acidification, at least during metabolic acidosis.

The post-natal chemosensory environment induces epigenetic changes in vomeronasal receptor gene expression and a bias in olfactory preference.

Vomeronasal stem cells are generated throughout the life of a mouse and differentiate into neurons that express one vomeronasal type 1 (V1r), one or two vomeronasal type 2 (V2r), or one olfactory receptor. Vomeronasal stem cells can be induced to differentiate into neurons by treatment with lipocalins from mouse urine or by epigenetic modification following treatment with histone deacetylase inhibitors. An important question is, do chemosensory signals, modify the detection capabilities of the vomeronasal organ and affect behaviour. Rearing mice in the presence of urine (and its pheromonal signals) derived from a different mouse strain, affected the behavioural preference for non-kin which were accompanied by changes in vomeronasal receptor expression. Significant changes in the expression of vomeronasal V1r, V2r and olfactory receptors, major urinary proteins, and a number of genes thought to be involved in transcriptional regulation were also observed following urine treatment. These results suggest that modification of a mouse's urinary environment may exert epigenetic effects on developing vomeronasal neurons, which modify the type of vomeronasal receptors that are expressed. This may provide a mechanism by which environmental changes are able to modify the detection capabilities of the vomeronasal organ to respond optimally to the most likely social environment that a mouse will encounter when mature.

Downregulation of vasopressin V1A receptors and activation of mitogen-activated protein kinase in rat mesangial cells cultured under high-glucose conditions.

SUMMARY: In the present study we examined the effects of high extracellular glucose concentrations on vasopressin (AVP) V(1A) receptor kinetics and signal transduction in cultured rat mesangial cells. Scatchard analysis of [(3) H]-AVP binding to mesangial cell plasma membranes showed that although high glucose (30 mmol/L) decreased V(1A) receptor numbers relative to cells cultured in normal glucose (10 mmol/L), receptor affinity was not affected. This V(1A) receptor downregulation was associated with an attenuated increase in AVP-stimulated cytosolic free calcium concentrations ([Ca(2+) ](i) ). In addition, high glucose increased both the basal and AVP-stimulated activity of the classic mitogen-activated protein kinase, namely extracellular signal-regulated kinase (ERK). Furthermore, high glucose induced activation of protein kinase C (PKC) in mesangial cells that could be inhibited by coincubation with the PKC inhibitor staurosporine (10 nmol/L). Staurosporine also markedly attenuated the high glucose-induced downregulation of V(1A) receptors on mesangial cells and blocked the depressed [Ca(2+) ](i) response and increased ERK activity induced by AVP. The results indicate that high extracellular glucose downregulates V(1A) receptors on rat mesangial cells and modulates their signal transduction properties via PKC activation.

Urine-concentrating defects exacerbate with age in male offspring with a low-nephron endowment.

Fetal uninephrectomy (uni-x) in male sheep at 100 days of gestation (term = 150 days) reduces overall nephron endowment without affecting birth weight. Offspring have a lower glomerular filtration rate (GFR) and elevated mean arterial pressure (MAP) at 6 mo of age. This study investigated whether this reduction in renal function was associated with impaired urine-concentrating ability at 6 mo of age and exacerbated with ageing (4 yr) and examined response to 1) nonpressor dose of exogenous arginine vasopressin (AVP; 0.2 µg·kg(-1)·h(-1) iv) and 2) 30 h of water deprivation. Basal MAP was higher in uni-x animals at both ages, and became further elevated with age compared with the sham group (elevation in MAP with age; sham: ~4 mmHg, uni-x: 9 mmHg, P(group × age) < 0.01). GFR declined with ageing in both groups with the decrease being greater with age in the uni-x group (further 26%, P(group × age) < 0.001). In response to AVP infusion, urine osmolality increased in both treatment groups; this response was significantly lower in the uni-x animals and became further reduced with ageing. Uni-x animals had reduced renal expression of vasopressin-2 receptor and aquaporin-2 at both ages (P < 0.01). The increase in plasma AVP levels in response to dehydration was similar between the treatment groups, suggesting the urine-concentrating defect was associated with these renal gene changes rather than defects in AVP secretion. Renal insufficiency due to a low-nephron endowment increases the risk of hypertension and chronic renal disease and may incur greater vulnerability to physiological challenges such as water deprivation as observed in the uni-x animals.

Emerging role of Akt substrate protein AS160 in the regulation of AQP2 translocation.

AS160, a novel Akt substrate of 160 kDa, contains a Rab GTPase-activating protein (GAP) domain. The present study examined the role of Akt and AS160 in aquaporin-2 (AQP2) trafficking. The main strategy was to examine the changes in AQP2 translocation in response to small interfering RNA (siRNA)-mediated AS160 knockdown in mouse cortical collecting duct cells (M-1 cells and mpkCCDc14 cells). Short-term dDAVP treatment in M-1 cells stimulated phosphorylation of Akt (S473) and AS160, which was also seen in mpkCCDc14 cells. Conversely, the phosphoinositide 3-kinase (PI3K) inhibitor LY 294002 diminished phosphorylation of Akt (S473) and AS160. Moreover, siRNA-mediated Akt1 knockdown was associated with unchanged total AS160 but decreased phospho-AS160 expression, indicating that phosphorylation of AS160 is dependent on PI3K/Akt pathways. siRNA-mediated AS160 knockdown significantly decreased total AS160 and phospho-AS160 expression. Immunocytochemistry revealed that AS160 knockdown in mpkCCDc14 cells was associated with increased AQP2 density in the plasma membrane [135 ± 3% of control mpkCCDc14 cells (n = 65), P < 0.05, n = 64] despite the absence of dDAVP stimulation. Moreover, cell surface biotinylation assays of mpkCCDc14 cells with AS160 knockdown exhibited significantly higher AQP2 expression [150 ± 15% of control mpkCCDc14 cells (n = 3), P < 0.05, n = 3]. Taken together, PI3K/Akt pathways mediate the dDAVP-induced AS160 phosphorylation, and AS160 knockdown is associated with higher AQP2 expression in the plasma membrane. Since AS160 contains a GAP domain leading to a decrease in the active GTP-bound form of AS160 target Rab proteins for vesicle trafficking, decreased expression of AS160 is likely to play a role in the translocation of AQP2 to the plasma membrane.

ACTH response to desmopressin in a patient with acromegaly; expression of corticotropin-releasing factor, urocortins and vasopressin V1b receptor in GH-producing pituitary adenoma.

GH-producing pituitary adenomas frequently co-produce other certain anterior pituitary hormones, such as prolactin (PRL). In contrast, GH-producing adenomas which express all of corticotropin-releasing factor (CRF), urocorin1 (Ucn1) and urocortin3 (Ucn3) have not been reported. A 39-year-old woman was admitted for evaluation of the pituitary tumor. The diagnosis of acromegaly was confirmed by elevated serum GH and IGF-I levels, and the absence of GH suppression by oral glucose tolerance test. ACTH response to desmopressin (DDAVP) was observed (plasma ACTH levels increased from 13.9 to 50.4 pg/ml at 90 min). Although it is known that ACTH response to DDAVP is considerably useful for the diagnosis of ACTH-dependent Cushing's syndrome, the diagnosis of Cushing's disease was not supported by the criteria. The patient underwent transsphenoidal resection of the pituitary tumor. Immunohistological examination confirmed a GH- and PRL-producing adenoma, whereas ACTH was negative. ACTH response to DDAVP disappeared after tumor removal. To determine the cause of preoperative ACTH response to DDAVP, we examined expression of CRF family peptides and vasopressin V1b receptor in the pituitary adenoma by immunohistochemistry. Immunohistochemistry revealed positive immunostaining for CRF, Ucn1, Ucn3 and vasopressin V1b receptor in the adenoma. These observations raised the possibility that DDAVP caused an ACTH response, perhaps via the paracrine effects of tumor-derived CRF and Ucn1. When ACTH response to DDAVP is observed in patients with pituitary tumor, not only the direct effect of DDAVP on ACTH secretion, but also a possible involvement of CRF and/or urocortins expressed in the pituitary adenoma, should be considered.

Intranasal oxytocin administration ameliorates social behavioral deficits in a POGZWT/Q1038R mouse model of autism spectrum disorder.

Autism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder characterized by core symptoms of impaired social behavior and communication. Recent studies have suggested that the oxytocin system, which regulates social behavior in mammals, is potentially involved in ASD. Mouse models of ASD provide a useful system for understanding the associations between an impaired oxytocin system and social behavior deficits. However, limited studies have shown the involvement of the oxytocin system in the behavioral phenotypes in mouse models of ASD. We have previously demonstrated that a mouse model that carries the ASD patient-derived de novo mutation in the pogo transposable element derived with zinc finger domain (POGZWT/Q1038R mice), showed ASD-like social behavioral deficits. Here, we have explored whether oxytocin (OXT) administration improves impaired social behavior in POGZWT/Q1038R mice and found that intranasal oxytocin administration effectively restored the impaired social behavior in POGZWT/Q1038R mice. We also found that the expression level of the oxytocin receptor gene (OXTR) was low in POGZWT/Q1038R mice. However, we did not detect significant changes in the number of OXT-expressing neurons between the paraventricular nucleus of POGZWT/Q1038R mice and that of WT mice. A chromatin immunoprecipitation assay revealed that POGZ binds to the promoter region of OXTR and is involved in the transcriptional regulation of OXTR. In summary, our study demonstrate that the pathogenic mutation in the POGZ, a high-confidence ASD gene, impairs the oxytocin system and social behavior in mice, providing insights into the development of oxytocin-based therapeutics for ASD.

Expression of Arginine Vasopressin Type 2 Receptor in Canine Mammary Tumours: Preliminary Results.

The aims of this study were to investigate the potential association of arginine vasopressin type 2 receptor (AVPR2) in canine mammary tumours with expression of oestrogen receptors α (ORα) and ß (ORß) and clinicopathological features of the neoplasms. Twenty-six canine mammary tumour samples (11 benign, 15 malignant) were immunolabelled for AVPR2, ORα and ORß antigens. Moderate to intense immunolabelling of AVPR2 antigen, found in all neoplasms, was not significantly associated with expression of ORα or ORß antigens or with clinicopathological features. These findings indicate a potential role for AVPR2 in the development of canine mammary tumours and the use of AVPR2-selective vasopressin analogues as therapeutic options.

Er Shen Wan extract alleviates polyuria and regulates AQP 2 and AVPR 2 in a rat model of spleen-kidney Yang deficiency-induced diarrhea.

ETHNOPHARMACOLOGICAL RELEVANCE: Er Shen Wan (ESW), has been empirically used for treating spleen-kidney Yang deficiency (SKYD) syndrome in Traditional Chinese medicine (TCM) for centuries and shows a variety of activities. The medicinal formula is a mixture of two component herbs, Psoraleae Fructus (PF, Bu-Gu-Zhi in Chinese) and Myristicae Semen (MS, Rou-Dou-Kou in Chinese). The current study was designed to evaluate ESWP antidiuretic treatment of polyuria and to explore potential mechanisms of renal water metabolism in the rat model of SKYD-induced diarrhea. MATERIALS AND METHODS: An animal model of 'SKYD-induced diarrhea syndrome' has been established to evaluate the therapeutic effect and action mechanism according to the clinical syndrome and symptoms. The optimal dose (3.5 g/kg) of ESWP was given to rats by gavage for two weeks. Urinary volumes after 24 h were recorded. After the end of the trial, macroscopic morphological and histological examination of the kidney were conducted. Serum levels of Arginine vasopressin (AVP) and aldosterone (ALD) were also measured. Additionally, quantitative real-time RT-PCR (RT-qPCR) and immunohistochemistry (IHC) analyses were performed to clarify the regulation of aquaporin 2 (AQP 2) and arginine vasopressin type 2 receptor (AVPR 2) in the kidney at the gene and tissue expression levels respectively. RESULTS: After the administration of ESWP, urinary output volume after 24 h was found to be significantly decreased in rats. Elevated plasma levels of AVP and ALD were detected. Histological kidney damage appeared to be impeded, and histological disease scores were reduced. In addition, the expression levels of AQP 2 and AVPR 2 were significantly increased. CONCLUSION: This study suggests that ESWP may elicit significant effects on the treatment of polyuria. Potential mechanisms at least partially involve hormone regulation, and alleviating renal pathological damage. Simultaneously, ESWP may alter renal water absorption by increasing AQP 2 and AVPR 2 expression levels. Thus, the in vivo experimental evidence indicates that ESWP has a therapeutic effect on the SKYD syndrome, which is consistent with its traditional usage.

Aberrant adrenal sensitivity to vasopressin in adrenal tumours associated with subclinical or overt autonomous hypercortisolism: is this explained by an overexpression of vasopressin receptors?

OBJECTIVE: Abnormal responsiveness to arginine vasopressin (AVP) was previously observed in cortisol-producing adrenocortical tumours but the mechanism remains unclear. The aim of this study was to characterize the effect of AVP on cortisol secretion from adrenocortical tumours compared to normal human adrenal gland. DESIGN: A multicentre study based on pharmacological, molecular and immunohistochemical experiments performed in adenomatous and normal adrenal tissues. PATIENTS: Twenty patients with adrenocortical adenomas and subclinical Cushing's syndrome (SCCS) or Cushing's syndrome (CS) were compared to six control normal subjects. MEASUREMENTS: In vivo and in vitro cortisol response to vasopressin, vasopressin receptor subtype mRNA measurement by real-time polymerase chain reaction (RT-PCR), immunohistochemical localization of AVP and its V1a receptor in tumour and normal adrenal tissues. RESULTS: Terlipressin in vivo enhanced cortisol plasma levels in 17/20 SCCS and 3/6 CS but in none of the control subjects. In vitro cortisol response to AVP was observed in nine tumours studied, with enhanced efficacy and/or potency of AVP in three SCCS tumours compared to normal tissues. AVP receptor subtype mRNA levels were similar in SCCS, CS cells and normal adrenal cells. Some SCCS tumour steroidogenic cells showed AVP and V1a receptor immunoreactivity. CONCLUSIONS: SCCS and CS adrenocortical tumours often exhibit in vivo and in vitro hyper-responsiveness to AVP, which is not related to vasopressin receptor overexpression, but may be explained by more efficient coupling pathways or by the indirect action of AVP through an autocrine/paracrine mechanism.

Developmental trajectories and influences of environmental complexity on oxytocin receptor and vasopressin 1A receptor expression in male and female prairie voles.

Nonapeptide receptors, like oxytocin receptor (OTR) and vasopressin 1a receptor (V1aR), modulate a variety of functions across taxa, and mediate phenotypic variation within and between species. Despite the popularity of studying nonapeptides in adults, developmental perspectives on properties of OTR and V1aR expression are lacking. Study of prairie voles (Microtus ochrogaster) has facilitated an understanding of mechanisms of social behavior and provides great potential to inform how early life experiences alter phenotype. We provide the first comprehensive profiling of OTR and V1aR in male and female prairie voles across postnatal development and into adulthood. Differences in receptor densities across the forebrain were region- and sex-specific. Postnatal changes in receptor expression fell into four themes: (a) constant over time, (b) increasing with age, (c) decreasing with age, or (d) peaking during late pre-weaning (postnatal day 15-21). We also examined the influence of post-weaning social and spatial enrichment (i.e., environmental complexity) on OTR and V1aR. Environmental complexity appeared to promote expression of OTR in males and females, and reduced expression of V1aR across several brain regions in males. Our results show that nonapeptide receptor profiles are plastic over development and suggest that different patterns of expression might represent functional differences in sensitivity to nonapeptide activation over a period when social environments are dynamic. Our results on environmental complexity suggest that nonapeptide sensitivity responds flexibly to different environmental contexts during development. Understanding the developmental trajectories of nonapeptide receptors provides a better understanding of the dynamic nature of social behavior and the underlying mechanisms.

Cullin 5 gene expression in the rat cerebral cortex and hippocampus following traumatic brain injury (TBI).

Cullin-5 (Cul-5), a member of the cullin gene family of scaffold proteins of E3 ubiquitin-ligase complexes, has a role in proteolysis and cell cycle regulation. We recently demonstrated that cul-5 mRNA is ubiquitously expressed in the central nervous system. The present study used quantitative real time polymerase chain reaction and western blotting to measure changes in cul-5 mRNA and Cul-5 protein expression, respectively, in the injured CNS in response to traumatic brain injury (TBI). cul-5 mRNA levels were significantly decreased in the ipsilateral rat cerebral cortex on Days 1 and 7, but not on Day 3 following TBI. In the ipsilateral hippocampus, cul-5 mRNA was significantly reduced on Day 1 after TBI. Cul-5 protein levels were significantly decreased in the ipsilateral rat cerebral cortex on Days 1-7 post-TBI while levels were significantly lower in the ipsilateral hippocampus on Days 3-7 post-TBI. Since Cul-5 is ubiquitously expressed in eukaryotic cells and is linked to proteasome-mediated protein degradation, it may have a role in CNS cell fate determination under conditions of traumatic stress.

Sex-Dependent Effects of Prenatal Stress on Social Memory in Rats: A Role for Differential Expression of Central Vasopressin-1a Receptors.

Prenatal stress (PNS) affects a number of traits in the offspring, including stress axis regulation, emotionality and cognition; however, much less is known about the effects of PNS on social memory and the underlying central mechanisms. In the present study, we investigated social preference, social memory under basal and stress conditions and olfactory memory for social and nonsocial odours in the adult offspring of dams exposed to social stress during late pregnancy. Given the key roles that the central oxytocin and vasopressin systems play in facilitating social memory, we further investigated the effects of PNS on the central expression of mRNA for oxytocin (Oxtr) and vasopressin-1a (Avpr1a) receptors. PNS did not affect social preference in either sex; however, social memory was impaired under basal conditions in PNS females but not PNS males. Accordingly, Avpr1a mRNA expression in the lateral septum and bed nucleus of stria terminalis (BNST) was unaltered in males but was significantly lower in PNS females compared to controls. No differences in Oxtr mRNA expression were detected between control and PNS offspring in either sex in any of the brain regions examined. Social memory deficits in PNS females persisted when social odours were used; however, this does not appear to be a result of impaired olfaction because memory for nonsocial odours was similar in control and PNS females. Under acute stress conditions, deficits in social memory were observed in both male and female control offspring; however, PNS males were unaffected. Moreover, acute stress facilitated social memory in PNS females and this was associated with an up-regulation of Avpr1a mRNA in the lateral septum and BNST. Our data support a role for altered signalling via central Avpr1a in PNS-induced sex-dependent changes in social memory and may have implications for understanding the aetiology of neurodevelopmental disorders characterised by social behaviour deficits in humans.

Reduced hypothalamic vasopressin secretion underlies attenuated adrenocorticotropin stress responses in pregnant rats.

We sought to explain decreased ACTH secretory responses to stress in pregnant rats by investigating hypothalamic CRH and vasopressin secretion and actions on anterior pituitary corticotrophs. In late pregnancy median eminence, CRH content was reduced (by 12%). Anterior pituitary proopiomelanocortin mRNA expression, measured by in situ hybridization but not radioimmunoassayed ACTH content, was also reduced (by 45% on d 21); CRH receptor (CRHR)1 mRNA expression was unaltered in pregnancy, but V1b receptor mRNA expression was reduced (by 19%). ACTH secretory responses, measured in jugular blood, to CRH (200 ng/kg iv) or vasopressin (1.7 microg/kg, iv) were reduced on d 21 vs. virgins (49% and 44%), but the response to combined CRH and vasopressin injection was intact. Either antalarmin (CRHR1 antagonist; 20 mg/kg ip) or dP(Tyr(Me)2),Arg-NH2(9))AVP (V1a/b antagonist; 10 microg/kg, iv) pretreatment reduced the ACTH secretory response to forced swimming (90 sec) in virgin rats (by 57% and 40%), but only antalarmin was effective in pregnant rats (53% decrease). In vitro, measuring ACTH secretion from acutely dispersed anterior pituitary cells showed increased corticotroph sensitivity in pregnancy to CRH and to CRH augmentation by vasopressin, attributable to increased intracellular cAMP action. Hence, in late pregnancy, reduced anterior pituitary CRHR1 or V1b receptor expression did not impair corticotroph responses to CRH or vasopressin. Rather, diminished secretagogue secretion in vivo accounts for reduced action of stress levels of exogenous CRH or vasopressin alone; the late pregnancy attenuated ACTH secretory response to swim stress is deduced to be due to reduced vasopressin release by parvocellular paraventricular nuclei neurones.

C-peptide increases the expression of vasopressin-activated calcium-mobilizing receptor gene through a G protein-dependent pathway.

OBJECTIVE: Although an increasing number of reports suggest that physiological concentrations of C-peptide protect against the development of diabetic nephropathy, possibly through the modulation of Na-K pump activity, the intracellular pathways controlled by C-peptide are still unrecognized. C-peptide and vasopressin share similar intracellular effects including the activation of calcium influx and endothelial nitric oxide synthase. Both hormones stimulate also the activity of Na-K pump activity. Whether the activity of C-peptide is mediated by the recently identified vasopressin-activated calcium-mobilizing receptor (VACM-1) has never been previously investigated. DESIGN AND METHODS: To clarify this issue, we evaluated the effect of C-peptide on VACM-1 RNA (measured by semiquantitative RT-PCR) and protein expression (measured by immunoblotting) in human skin fibroblasts (where a specific binding of C-peptide was demonstrated) and in human mesangial cells, the cellular target of diabetic nephropathy. RESULTS: C-peptide-induced activation of VACM-1 was demonstrated in fibroblasts from six healthy individuals (0.51+/-0.1 vs 1.48+/-0.4, arbitrary units+/-s.e., P = 0.025). This finding was paralleled by an increased VACM-1 protein expression (5.64+/-1.0 vs 8.47+/-1.2, arbitrary units+/-s.e., P= 0.043). Similar results were confirmed in three independent cultures of human mesangial cells. VACM-1 activation in fibroblasts was insensitive to phosphatidylinositol-3-kinase inhibitor LY294002, but was inhibited by pertussis toxin, suggesting that activation of VACM-1 could be mediated by a G protein-coupled receptor. CONCLUSIONS: This study demonstrates for the first time that C-peptide activates VACM-1, possibly through a G protein-coupled receptor. Further studies are needed to clarify whether VACM-1 is involved in the protective effect of C-peptide against the development of diabetic nephropathy.