V1a Receptor Expression Research Articles

Desmopressin inhibit the proliferation and cellular migration in the OV‐90 ovarian cancer cell line

Epithelial ovarian cancer (EOC) is the most common and lethal of the ovarian neoplasms, frequently it is detected at advanced stages of the disease resulting in 60–70% of the cases in recurrence and less responsive to chemotherapy. Currently the role played by the neurohypophyseal hormone arginine vasopressin (AVP) and its receptors in the development of EOC is unknown. The purpose of this study was to evaluate the action of desmopressin (DDAVP), an AVP V2 receptor agonist on the cell proliferation and cell migration in cells from the OV‐90 cell line. Cell proliferation was evaluated with the proliferation marker Ki67, whereas the cells migration was evaluated by the wound assay. The AVP V1a and V2 receptors expression were assessed by immunofluorescence. Cell cultures were stimulated during 12, 24, 36 and 48 hours with DDAVP (500 to 1500 mM). In order to discard the cytotoxicity of DDAVP on the OV‐90 cell cultures in control and stimulated cultures the Cytotox 96 kit was used. The experiments were performed three times by duplicate. The results showed that the expression of AVP V1a and V2 receptors are present in both DDAVP stimulated and‐non stimulated cultures. On the other hand in comparison with the control cultures, doses of 1000mM of DDAVP significantly (p<0.05) inhibit both cell proliferation and cellular migration. Present results also suggests a possible inhibitory role of DDAVP on proliferation and cellular migration in the OV‐90 cell lines of epithelial ovarian cancer.Support or Funding InformationUniversidad Autónoma de Aguascalientes PIFF14‐1 and CONACYT 221262. México

The influence of post-infarct heart failure and high fat diet on the expression of apelin APJ and vasopressin V1a and V1b receptors

Vasopressin and apelin are reciprocally regulated hormones which are implicated in the pathophysiology of heart failure and the regulation of metabolism; however, little is known about their interactions under pathological conditions. In this study, we determined how post-infarct heart failure (HF) and a high fat diet (HFD) affect expression of the apelin APJ receptor (APJR) and the V1a (V1aR) and V1b (V1bR) vasopressin receptors in the hypothalamus, the heart, and the retroperitoneal adipose tissue. We performed experiments in male 4-week-old Sprague Dawley rats. The animals received either a normal fat diet (NFD) or a HFD for 8 weeks, then they underwent left coronary artery ligation to induce HF or sham surgery (SO), followed by 4 weeks of NFD or HFD. The HF rats showed higher plasma concentration of NT-proBNP and copeptin. The HF reduced the APJR mRNA expression in the hypothalamus. The APJR and V1aR protein levels in the hypothalamus were regulated both by HF and HFD, while the V1bR protein level in the hypothalamus was mainly influenced by HF. APJR mRNA expression in the heart was significantly higher in rats on HFD, and HFD affected the reduction of the APJR protein level in the right ventricle. The regulation of APJR, V1aR and V1bR expression in the heart and the retroperitoneal adipose tissue were affected by both HF and HFD. Our study demonstrates that HF and HFD cause significant changes in the expression of APJR, V1aR and V1bR, which may have an important influence on the cardiovascular system and metabolism.

Dynamic Modulation of Mouse Locus Coeruleus Neurons by Vasopressin 1a and 1b Receptors.

The locus coeruleus (LC) is a brainstem nucleus distinguished by its supply of noradrenaline throughout the central nervous system. Apart from modulating a range of brain functions, such as arousal, cognition and the stress response, LC neuronal excitability also corresponds to the activity of various peripheral systems, such as pelvic viscera and the cardiovascular system. Neurochemically diverse inputs set the tone for LC neuronal activity, which in turn modulates these adaptive physiological and behavioral responses essential for survival. One such LC afferent system which is poorly understood contains the neurohormone arginine-vasopressin (AVP). Here we provide the first demonstration of the molecular and functional characteristics of the LC-AVP system, by characterizing its receptor-specific modulation of identified LC neurons and plasticity in response to stress. High resolution confocal microscopy revealed that immunoreactivity for the AVP receptor 1b (V1b) was located on plasma membranes of noradrenergic and non-noradrenergic LC neurons. In contrast, immunoreactivity for the V1a receptor was exclusively located on LC noradrenergic neurons. No specific signal, either at the mRNA or protein level, was detected for the V2 receptor in the LC. Clusters immunoreactive for V1a-b were located in proximity to profiles immunoreactive for GABAergic and glutamatergic synaptic marker proteins. AVP immunopositive varicosities were also located adjacent to labeling for such synaptic markers. Whole-cell patch clamp electrophysiology revealed that the pharmacological activation of V1b receptors significantly increased the spontaneous activity of 45% (9/20) of recorded noradrenergic neurons, with the remaining 55% (11/20) of cells exhibiting a significant decrease in their basal firing patterns. Blockade of V1a and V1b receptors on their own significantly altered LC neuronal excitability in a similar heterogeneous manner, demonstrating that endogenous AVP sets the basal LC neuronal firing rates. Finally, exposing animals to acute stress increased V1b, but not V1a receptor expression, whilst decreasing AVP immunoreactivity. This study reveals the AVP-V1a-b system as a considerable component of the LC molecular architecture and regulator of LC activity. Since AVP primarily functions as a regulator of homeostasis, the data suggest a novel pathway by modulating the functioning of a brain region that is integral to mediating adaptive responses.

Chronic Overexpression of Bradykinin in Kidney Causes Polyuria and Cardiac Hypertrophy

Acute intra-renal infusion of bradykinin increases diuresis and natriuresis via inhibition of vasopressin activity. However, the consequences of chronically increased bradykinin in the kidneys have not yet been studied. A new transgenic animal model producing an excess of bradykinin by proximal tubular cells (KapBK rats) was generated and submitted to different salt containing diets to analyze changes in blood pressure and other cardiovascular parameters, urine excretion, and composition, as well as levels and expression of renin-angiotensin system components. Despite that KapBK rats excrete more urine and sodium, they have similar blood pressure as controls with the exception of a small increase in systolic blood pressure (SBP). However, they present decreased renal artery blood flow, increased intrarenal expression of angiotensinogen, and decreased mRNA expression of vasopressin V1A receptor (AVPR1A), suggesting a mechanism for the previously described reduction of renal vasopressin sensitivity by bradykinin. Additionally, reduced heart rate variability (HRV), increased cardiac output and frequency, and the development of cardiac hypertrophy are the main chronic effects observed in the cardiovascular system. In conclusion: (1) the transgenic KapBK rat is a useful model for studying chronic effects of bradykinin in kidney; (2) increased renal bradykinin causes changes in renin angiotensin system regulation; (3) decreased renal vasopressin sensitivity in KapBK rats is related to decreased V1A receptor expression; (4) although increased renal levels of bradykinin causes no changes in mean arterial pressure (MAP), it causes reduction in HRV, augmentation in cardiac frequency and output and consequently cardiac hypertrophy in rats after 6 months of age.

Aging increases the expression of vasopressin receptors in both the kidney and urinary bladder.

The goal of this study was to determine whether aging effects the expression of V1a and V2 vasopressin receptors in the urinary bladder mucosa (UBM) and kidney. UBM and kidneys were obtained from young (3 months-of-age) and old (25-30 months-of-age) female Fisher 344 rats. Tissue samples were analyzed by western blotting for V1a and V2 receptor expression, and rat plasma levels of vasopressin levels were measured by ELISA. V1a and V2 receptors were detected in both the UBM and kidneys. Aging significantly (P < 0.05) increased the expression of V2 receptors by 2.80 ± 0.52 and 6.52 ± 1.24-fold in the UBM and kidneys, respectively. Aging also increased V1a receptor expression in the kidneys (5.52 ± 1.05 fold; P < 0.05), but not in the UBM. To the best of our knowledge, because this is the first detection of V2 receptors in the mammalian bladder mucosa, we also probed human UBM for V2 receptors and observed high expression in human UBM. Unlike V1a and V2 receptors, aging had only a minor effect on plasma vasopressin levels (8% increase). V2 receptors are substantially increased in the aging UBM. The role of these receptors in UBM is as yet undefined, but given their presence and action in the kidneys, the possible effect of these receptors in free water regulation should be considered. The large age-related increase in the expression of V2 receptors in both the UBM and kidney may contribute to the effectiveness of desmopressin in age-related nocturia.

Central interaction between the apelinergic and vasopressinergic systems in the regulation of the hemodynamics parameters in rats maintained on high fat diet

IntroductionIt seems that changes in expression of APJ apelin and vasopressin V1a and V1b receptors may significantly affect action and interactions of these two peptides, can play important role in cardiovascular regulation in different pathophysiological states such obesity. Apelin (APLN) is one of adipokines; its dysregulation has been implicated in obesity and type II diabetes. APLN its receptor APJ are co‐localized with vasopressin (AVP) in paraventricular (PVN) and supraoptic (SON) nuclei of the hypothalamus. It has been suggested that the apelinergic system may play an important role in the regulation of the vasopressinergic neurons activity. Thus, changes in expression of APJ and V1a and V1b receptors may significantly affect action and interactions of these two peptides, and contribute to cardiovascular dysregulation in different pathological states.PurposeThe aim of this project is to test the hypothesis the central dysregulation of APJ and V1a and V1b receptors may affect the apelin‐vasopressin interaction and contribute to changes in the hemodynamic parameters in obesity.MethodsSprague‐Dawley rats were on maintained on high fat diet (HFD) or a normal fat diet (NFD). Animals in experimental groups had intracerebroventricular (ICV) cannula implants for delivery of tested substances and abdominal aorta catheters for measuring mean arterial blood pressure (MABP) and heart rate (HR). Group I rats had ICV infusion of saline (NaCl) or/and V1a receptor antagonist (V1aRANT) or/and apelin‐13 (APLN‐13). Group II rats had ICV infusion of NaCl or/and APJ antagonist (F13A) or/and AVP. Brain tissue was collected from additional groups, for the analyses of mRNA expression and protein level of APJ, V1a, and V1b receptors. Consent was obtained from The Local Animal Research Ethics Committee (37/2015).ResultsInfusion of V1aRANT resulted in a significant decrease in MABP in both NFD and HFD; the decrease was greater in HFD. Infusion of APLN‐13 alone resulted in increased MABP only in NFD rats; this effect was absent when infusion of APLN‐13 was preceded by infusion of V1aRANT. Infusion of APLN‐13 preceded by infusion of V1aRANT resulted in decreased HR only in HFD rats. ICV infusion of F13A resulted in a significant decrease in MABP in both NFD and HFD rats; this decrease was greater in NFD rats. Infusion of AVP resulted in an increase in both MABP and HR only in HFD rats. There was no difference in hypothalamic mRNA expression of APJ and V1b receptors between the NFD and HFD rats. Expression of V1a receptor was significantly lower in HFD rats compared to NFD rats. The protein levels of APJ, V1a, and V1b receptors in the hypothalamus were significantly higher in HFD rats compared to NFD rats.ConclusionThese results provide evidence for the involvement of receptor V1a receptor in the regulation of blood pressure by centrally acting apelin. Furthermore, our studies suggest that the interaction of the apelinergic and vasopressinergic system may play an important role in central regulation of cardiovascular system.Support or Funding InformationFunding: Preludium; National Science Centre (UMO‐2016/21/N/NZ4/03758D).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Role of Vasopressin on Intrinsic Cardiac Activity in Conscious Wistar Rats.

BackgroundThe effects of vasopressin on cardiac chronotropism are controversial in different species.ObjectiveTo investigate if vasopressin can influence the cardiac intrinsic activity in conscious Wistar rats.MethodsAll the procedures of this study were approved by the Animal ethics committee (protocol #02/2016). Adult male Wistar rats underwent to a cannulation of the femoral artery and vein for mean arterial pressure (MAP) and heart rate (HR) recordings and drug infusions, respectively, in conscious rats, 24 h after the surgical procedures. After baseline recordings, i.v. atropine 2 mg/kg and i.v. metoprolol 1.7 mg/kg were injected with 5 min interval. After 10 min, i.v. vasopressin 0.0625 mg/mL/5 min (N=6) or saline (1 mL/5 min) (N=6) were infused and the variables were recorded for additional 10 min. Gene and protein expression of V1a, V1b and V2 subtype receptors for AVP were also carried in the right atrium by qPCR and Western Blotting, respectively. The AVP receptor subtypes were also labeled by immunofluorescence technique in the right atrium.ResultsVasopressin evoked bradycardic (−51±5 bpm) and pressor responses (39±6 mmHg) compared to baseline post‐autonomic blockade (130 ±8 mmHg and 406±16 bpm). Saline did not change HR (1±4 bpm) and MAP (−3±1 mmHg) compared to baseline after autonomic blockade (120±5 mmHg and 411±52 bpm). All subtypes of AVP receptors were expressed in the right atrium by qPCR, Western Blotting and immunofluorescence.ConclusionThe bradycardia elicited by vasopressin after cardiac autonomic blockade suggests that vasopressin can affect the cardiac intrinsic activity binding to the receptors in the right atrium.Support or Funding InformationFinancial support: FAPESP, CNPq and NEPAS‐FMABC.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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, β2, β3 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.

Oxytocin produces thermal analgesia via vasopressin-1a receptor by modulating TRPV1 and potassium conductance in the dorsal root ganglion neurons.

Recent studies have provided several lines of evidence that peripheral administration of oxytocin induces analgesia in human and rodents. However, the exact underlying mechanism of analgesia still remains elusive. In the present study, we aimed to identify which receptor could mediate the analgesic effect of intraperitoneal injection of oxytocin and its cellular mechanisms in thermal pain behavior. We found that oxytocin-induced analgesia could be reversed by d(CH2)5[Tyr(Me)2,Dab5] AVP, a vasopressin-1a (V1a) receptor antagonist, but not by desGly-NH2-d(CH2)5[DTyr2, Thr4]OVT, an oxytocin receptor antagonist. Single cell RT-PCR analysis revealed that V1a receptor, compared to oxytocin, vasopressin-1b and vasopressin-2 receptors, was more profoundly expressed in dorsal root ganglion (DRG) neurons and the expression of V1a receptor was predominant in transient receptor potential vanilloid 1 (TRPV1)-expressing DRG neurons. Fura-2 based calcium imaging experiments showed that capsaicin-induced calcium transient was significantly inhibited by oxytocin and that such inhibition was reversed by V1a receptor antagonist. Additionally, whole cell patch clamp recording demonstrated that oxytocin significantly increased potassium conductance via V1a receptor in DRG neurons. Taken together, our findings suggest that analgesic effects produced by peripheral administration of oxytocin were attributable to the activation of V1a receptor, resulting in reduction of TRPV1 activity and enhancement of potassium conductance in DRG neurons.

Over-expression of V1A receptors in PVN modulates autonomic cardiovascular control

The hypothalamic paraventricular nucleus (PVN) is a key integrative site for the neuroendocrine control of the circulation and of the stress response. It is also a major source of the neuropeptide hormone vasopressin (VP), and co-expresses V1a receptors (V1aR). We thus sought to investigate the role of V1aR in PVN in cardiovascular control in response to stress. Experiments were performed in male Wistar rats equipped with radiotelemetric device. The right PVN was transfected with adenoviral vectors (Ads) engineered to over-express V1aR along with an enhanced green fluorescent protein (eGFP) tag. Control groups were PVN transfected with Ads expressing eGFP alone, or wild-type rats (Wt). Rats were recorded with and without selective blockade of V1aR (V1aRX) in PVN under both baseline and stressed conditions. Blood pressure (BP), heart rate (HR), their short-term variabilities, and baroreflex sensitivity (BRS) were evaluated using spectral analysis and the sequence method, respectively. Under baseline physiological conditions,V1aR rats exhibited reduced BRS and a marked increase of BP and HR variability during exposure to stress. These effects were all prevented by V1aRX pretreatment. In Wt rats, V1aRX did not modify cardiovascular parameters under baseline conditions, and prevented BP variability increase by stress. However, V1aRX pretreatment did not modify baroreflex desensitization by stress in either rat strain. It follows that increased expression of V1aR in PVN influences autonomic cardiovascular regulation and demarcates vulnerability to stress. We thus suggest a possible role of hypothalamic V1aR in cardiovascular pathology.

Early Life Manipulations of the Nonapeptide System Alter Pair Maintenance Behaviors and Neural Activity in Adult Male Zebra Finches.

Adult zebra finches (T. guttata) form socially monogamous pair bonds characterized by proximity, vocal communication, and contact behaviors. In this experiment, we tested whether manipulations of the nonapeptide hormone arginine vasotocin (AVT, avian homolog of vasopressin) and the V1a receptor (V1aR) early in life altered species-typical pairing behavior in adult zebra finches of both sexes. Although there was no effect of treatment on the tendency to pair in either sex, males in different treatments exhibited profoundly different profiles of pair maintenance behavior. Following a brief separation, AVT-treated males were highly affiliative with their female partner but sang very little compared to Controls. In contrast, males treated with a V1aR antagonist sang significantly less than Controls, but did not differ in affiliation. These effects on behavior in males were also reflected in changes in the expression of V1aR and immediate early gene activity in three brain regions known to be involved in pairing behavior in birds: the medial amygdala, medial bed nucleus of the stria terminalis, and the lateral septum. AVT males had higher V1aR expression in the medial amygdala than both Control and antagonist-treated males and immediate early gene activity of V1aR neurons in the medial amygdala was positively correlated with affiliation. Antagonist treated males showed decreased activity in the medial amygdala. In addition, there was a negative correlation between the activity of V1aR cells in the medial bed nucleus of the stria terminalis and singing. Treatment also affected the expression of V1aR and activity in the lateral septum, but this was not correlated with any behaviors measured. These results provide evidence that AVT and V1aR play developmental roles in specific pair maintenance behaviors and the neural substrate underlying these behaviors in a bird.

Vasopressin-induced mouse urethral contraction is modulated by caveolin-1

Caveolae are 50–100nm large invaginations in the cell membrane that are considered to play roles in receptor signaling. Here we aimed to investigate the expression and distribution of the arginine-vasopressin (AVP) V1a receptor and its functional dependence on caveolin-1 (Cav1) in the mouse urethra. Female Cav1 knockout (KO) and wild type (WT) mice were used, and urethral preparations were micro-dissected for mechanical experiments. Methyl-β-cyclodextrin (mβcd) was used to deplete cholesterol and to disrupt caveolae. Protein expression and localization was determined using immunofluorescence and western blotting and transcript expression was determined by qRT-PCR. We found that Cav1 and AVP V1a receptors were expressed in urethral smooth muscle cells with apparent co-localization at the cell membrane. AVP caused urethral contraction that was inhibited by the V1a receptor antagonist SR49059. Concentration–response curves for AVP were right-shifted and maximal contraction was reduced in Cav1 KO mice and after mβcd treatment. In addition to caveolin-1 we also detected caveolin-2, cavin-1 and cavin-3 in the mouse urethra by western blotting. Caveolin-2, cavin-1 and cavin-3 as well as V1a receptor expression was reduced in KO urethra. We conclude that AVP regulates urethral contractility via the V1a receptor through a Cav1-dependent mechanism involving, in part, altered V1a receptor expression.

Altered expression of V1a receptors mRNA in the brain and kidney after myocardial infarction and chronic stress

Vasopressin released during myocardial infarction and in response to stress regulates blood pressure through multiple actions exerted in the brain, cardiovascular system and kidney. The aim of the present study was to determine whether myocardial infarction influences expression of vasopressin V1a receptor (V1aR) mRNA and protein in the brain and kidney and whether stress has an impact on expression of these parameters during the post-infarct state. Male, adult Sprague Dawley rats were subjected to myocardial infarction or sham surgery. Seven days later some rats were exposed to mild stress for 4weeks whereas other stayed at rest. Tissue fragments were harvested from four groups of rats (control, infarct, stress, infarct+stress). Expression of V1aR mRNA (Real time PCR) was determined in the preoptic, diencephalic, mesencephalopontine and medullary regions of the brain and in the renal cortex and medulla. Protein V1aR expression (Western blotting) was determined in the brain mesencephalopontine region and in the kidney medulla. In the preoptic, diencephalic, and mesencephalopontine regions, V1aR mRNA expression was significantly lower in the infarcted rats than in the sham-operated unstressed controls. The infarcted rats manifested also lower expression of V1aR protein in the mesencephalopontine region than the other groups. The stressed group demonstrated significantly higher V1aR mRNA expression in the brain medulla and in the renal cortex and renal medulla than the control group. In all brain regions and in the kidney, V1aR mRNA expression was significantly higher in the stressed rats than in the infarcted rats. The stressed rats showed also higher expression of V1aR protein in the renal medulla than the other groups. It is concluded that myocardial infarction and chronic stress cause significant but differential changes in the regulation of V1a receptors expression in the brain and the kidney.

Age-dependent regulation of renal vasopressin V1A and V2 receptors in rats with genetic hypertension: implications for the treatment of hypertension

The role of arginine vasopressin (AVP) as a hypertensive hormone remains controversial. We have previously reported that intervention with a V1A receptor antagonist in 6-week-old prehypertensive spontaneously hypertensive rats (SHR) for 4 weeks attenuated the subsequent development of hypertension in adult SHR. This study assessed the age-dependent regulation of plasma AVP levels and kidney V1A and V2 receptor expression during the development of hypertension in SHR and in normotensive Sprague Dawley rats. Systolic blood pressure (SBP), plasma AVP, and plasma renin activity (PRA) and kidney V1A and V2 receptor expression were assessed. SHR were studied at three ages: prehypertensive (6 weeks), developed hypertension (10 weeks), and established hypertension (16 weeks). SBP increased with age in SHR (P < .01) and both plasma AVP (P < .01) and PRA (P < .05) were increased in 10-week-old SHR. Renal medulla V1A receptor gene expression decreased in 10-week and 16-week-old SHR (P < .01), with a reduction in V1A receptor protein in the inner medulla of 16-week-old SHR (P < .05) compared with young SHR. There was no change in V2 receptor expression during the development of hypertension. In normotensive rats, plasma AVP, PRA, and kidney V1A and V2 receptor expression were unchanged over time. These data suggest that in SHR, activation of plasma AVP and the renal V1A receptor occurs during developing hypertension, with downregulation when hypertension is established. The use of V1A receptor antagonists in prehypertension may provide a unique opportunity for the prevention of hypertension in high-risk individuals.

The roles of V1a vasopressin receptors in blood pressure homeostasis: a review of studies on V1a receptor knockout mice

A prompt rise in blood pressure occurs when arginine-vasopressin is administered in quantities adequate to activate vascular V1a subtype vasopressin receptors. However, it has been controversial whether the endogenous vasopressin-V1a system contributes to the maintenance of basal blood pressure during normal development and aging. Mutant mice lacking the V1a receptor gene (V1a(-/-)) show significantly lower blood pressure compared to control mice, without a notable change in heart rate. In V1a(-/-) mice, arterial baroreceptor reflexes were attenuated due to malfunctioning baroreflex center, and the mice's circulating blood volume was significantly reduced. In line with this reduction in circulating blood volume, adrenocortical hormone release was attenuated; plasma aldosterone levels were reduced and adrenocorticotropic hormone-stimulated corticosteroid release was attenuated. In addition, V1a receptor expression was detected in macula densa cells of the kidneys, which may have facilitated renin production from the juxtaglomerular cells. Deletion of the V1a receptor appears to impact the renin-angiotensin-aldosterone system. Studies on V1a(-/-) mice revealed that non-vascular V1a receptors in the central nervous system and peripheral tissues play critical roles in the maintenance of blood pressure homeostasis.

Locally released vasopressin increases presympathetic PVN neuronal activity in a calcium‐dependent manner

Accumulating evidence indicates that the vasopressin (VP) is locally released within the supraoptic and paraventricular (PVN) nuclei, autoregulating VP neuronal activity. Here, we tested if intranuclear VP release also influences presympathetic PVN neuronal activity. Patch‐clamp recordings from presympathetic PVN‐RVLM neurons showed that focal application of VP (1µM) evoked an inward current (~8pA, P&lt; 0.002), depolarized Vm (4mV, P&lt; 0.0001), and increased PVN‐RVLM firing activity (~780%, P&lt; 0.0001), effects blocked by a V1a receptor antagonist. The expression of V1a receptors in PVN‐RVLM neurons was confirmed immunohistochemically. V1a receptor blockade hyperpolarized Vm (~4mV, P&lt; 0.001) and reduced ongoing firing activity of PVN‐RVLM neurons (~70%, P&lt; 0.002). VP excitatory effect on PVN‐RVLM neurons was blocked by rapid chelation of intracellular Ca2+ (P&lt; 0.02), but was not dependent on an influx of extracellular Ca2+. Finally, the effect of endogenously released VP was dependent on the activity of endogenous aminopeptidases. In summary, our results indicate that endogenously released VP, likely from a magnocellular neurosecretory source, tonically excites presympathetic PVN neurons, constituting a functionally relevant intercellular signaling pathway in the generation of homeostatic patterns of neuroendocrine and autonomic activities by the PVN. Supported by NIH HL68725

A possible association between aldosterone response to vasopressin and circadian change of aldosterone in the patients with aldosterone-producing adenoma

Vasopressin was reported to stimulate secretion of both cortisol and aldosterone through eutopic V1a receptors in adrenal gland. Recently, adrenal hyper-responsiveness of plasma cortisol to vasopressin with eutopic overexpession of V1a receptors has been reported in Cushing’s syndrome, such as a majority of cases of ACTH-independent macronodular adrenal hyperplasia and some cases of Cushing’s adenomas. There were a few reports regarding the aldosterone response to vasopressin in aldosterone-producing adenoma. The aim of our study was to investigate the aldosterone response to vasopressin and its pathophysiological roles in the patients with aldosterone-producing adenoma. Vasopressin-loading test was performed in 10 patients with aldosterone-producing adenoma, and in 16 patients with non-functioning adrenal tumors. The roles of the aldosterone response to vasopressin were analyzed in terms of hormonal secretion and the expression of V1a receptor mRNA on the operated adrenal gland in aldosterone-producing adenoma. We found that (1) a varying aldosterone response to vasopressin was observed, (2) absolute response of plasma aldosterone in aldosterone-producing adenoma was significantly higher than that in non-functioning tumor, (3) aldosterone response rate to vasopressin was significantly and negatively correlated with the decline rate (%) in plasma aldosterone from morning to evening in aldosterone-producing adenoma, (4) V1a receptor mRNA was expressed at various values in aldosterone-producing adenoma, and (5) surgical removal of aldosterone-producing adenoma eliminated the aldosterone response to vasopressin observed in patients with aldosterone-producing adenoma. These findings indicated that vasopressin might be involved in the coordination of aldosterone secretion through eutopic expression of V1a receptor in aldosterone-producing adenoma.

Role of nuclear factor-κB-dependent induction of cytokines in the regulation of vasopressin V1A-receptors during cecal ligation and puncture-induced circulatory failure*

Here we characterize the impact of nuclear factor-kappaB and cytokines on cecal ligation and puncture-induced circulatory failure and regulation of vasopressin V1A-receptors during inflammation. Prospective animal trial. Laboratory of the Department of Anesthesiology. Male C57/BL6 mice. The effects of cecal ligation and puncture on hemodynamic parameters and V1A-receptor expression were measured in cytokine knock-out mice, in mice with/without treatment with glucocorticoids or NF-kappaB-inhibitors, in mice pretreated with small interfering RNA silencing NF-kappaB and in mice treated with V1 receptor agonists. Furthermore, the effects of cytokines on V1A-receptor expression were determined. Cecal ligation and puncture resulted in a hyperdynamic circulatory failure with diminished blood pressor dose response to V1 receptor agonists and down-regulation of V1A-receptors. Dexamethasone inhibited proinflammatory cytokine production and attenuated cecal ligation and puncture-induced cardiovascular failure in parallel with attenuated down-regulation of V1A-receptor expression. Tumor necrosis factor-alpha, interleukin-1beta, interferon-gamma or interleukin-6 dose-dependently decreased V1A-receptor expression, whereas cecal ligation and puncture-induced down-regulation of V1A-receptors was not affected in cytokine knock-out mice. In contrast, inhibition of NF-kappaB strongly reduced induction of cytokines, prevented septic circulatory failure and down-regulation of V1A-receptor gene expression and improved survival of septic animals. Our data demonstrate that down-regulation of V1A-receptor expression during sepsis may be due to proinflammatory cytokines. Our findings explain the failure of therapeutic strategies targeting single cytokines as well as the success of glucocorticoid therapy and define a critical role for NF-kappaB in the pathogenesis of septic shock.

Axial heterogeneity of vasopressin-receptor subtypes along the human and mouse collecting duct

Vasopressin and vasopressin antagonists are finding expanded use in mouse models of disease and in clinical medicine. To provide further insight into the physiological role of V1a and V2 vasopressin receptors in the human and mouse kidney, intrarenal localization of the receptors mRNA was determined by in situ hybridization. V2-receptor mRNA was predominantly expressed in the medulla, whereas mRNA for V1a receptors predominated in the cortex. The segmental localization of vasopressin-receptor mRNAs was determined using simultaneous in situ hybridization and immunohistochemistry for segment-specific markers, including aquaporin-2, Dolichos biflorus agglutinin, epithelial Na channels, Tamm Horsfall glycoprotein, and thiazide-sensitive Na(+)-Cl(-) cotransporter. Notably, V1a receptor expression was exclusively expressed in V-ATPase/anion exchanger-1-labeled alpha-intercalated cells of the medullary collecting duct in both mouse and human kidney. In cortical collecting ducts, V1a mRNA was more widespread and detected in both principal and intercalated cells. V2-receptor mRNA is diffusely expressed along the collecting ducts in both mouse and human kidney, with higher expression levels in the medulla. These results demonstrate heterogenous axial expression of both V1a and V2 vasopressin receptors along the human and mouse collecting duct. The restricted expression of V1a-receptor mRNA in intercalated cells suggests a role for this receptor in acid-base balance. These findings further suggest distinct regulation of renal transport function by AVP through V1a and V2 receptors in the cortex vs. the medulla.

Expression of V1A and GRP receptors leads to cellular transformation and increased sensitivity to substance-P analogue-induced growth inhibition

Small-cell lung cancer (SCLC) is a particularly aggressive cancer, which metastasises early. Despite initial sensitivity to radio- and chemo-therapy, it invariably relapses, so that the 2-year survival remains less than 5%. Neuropeptides particularly arginine vasopressin (AVP) and gastrin-releasing peptide (GRP) act as autocrine and paracrine growth factors and the expression of these and their receptors are a hallmark of the disease. Substance-P analogues including [D-Arg1,D-Phe5,D-Trp7,9,Leu11]-substance-P (SP-D) and [Arg6,D-Trp7,9,NmePhe8]-substance-P (6–11) (SP-G) inhibit the growth of SCLC cells by modulating neuropeptide signalling. We show that GRP and V1A receptors expression leads to the development of a transformed phenotype. Addition of neuropeptide provides some protection from etoposide-induced cytotoxicity. Receptor expression also leads to an increased sensitivity to substance-P analogue-induced growth inhibition. We show that SP-D and SP-G act as biased agonists at GRP and V1A receptors causing blockade of Gq-mediated Ca2+ release while directing signalling to activate ERK via a pertussis toxin-sensitive pathway. This is the first description of biased agonism at V1A receptors. This unique pharmacology governs the antiproliferative properties of these agents and highlights their potential therapeutic potential for the treatment of SCLC and particularly in tumours, which have developed resistance to chemotherapy.