The effect of vasopressin 1b receptors (V1bRs) blockade on the HPA axis activity in rats exposed to acute heat stress

Abstract

SUMMARYThermal stressors such as low and high ambient temperature elicit an abundance of neuroendocrine responses including activation of the hypothalamo-pituitary-adrenal (HPA) axis and arginine vasopressin (AVP) release. The exposure to heat is a particularly interesting model for studying AVP action because this kind of stressor represents not only an unpleasant experience but also a threat to osmotic homeostasis. As AVP has long been recognized as a hormone involved in the modulation of HPA axis activity, the aim of this study was to elucidate the role of AVP in acutely heat-exposed rats using Nelivaptan, a selective vasopressin 1b receptor (V1bR) antagonist. Rats were exposed to high ambient temperature (38°C) for 60min. The circulating hormones were determined by ELISA or chemiluminescence, and intrapituitary adrenocorticotropic hormone (ACTH) and V1bR level were determined by western blot. The results obtained show that V1bR blockade negatively affected the increase in blood ACTH caused by heat exposure. This treatment alone, or in combination with Nelivaptan, decreased intrapituitary V1bR levels while circulating AVP concentration was increased under the same conditions. Furthermore, a strong correlation was observed between blood ACTH and corticosterone concentration. In conclusion, our results directly confirm the positive role of AVP in the regulation of ACTH secretion from the pituitary in animals exposed to heat. Moreover, the results suggest that AVP from the general circulation influences pituitary V1bR.

Arginine Vasopressin and Arginine Vasopressin Receptor 1b Involved in Electroacupuncture-Attenuated Hypothalamic-Pituitary-Adrenal Axis Hyperactivity in Hepatectomy Rats

“…To elucidate the molecular mechanism of EA application, rats were given intraperitoneal (i.p.) injection of the vehicle (1 mL/kg, 5% DMSO, 95% saline) or nelivaptan (5 mL/kg, Axon 1114, Axon Medchem BV Amsterdam, Groningen, the Netherlands) or d [Leu 4 , Lys 8 ] vasopressin (0.3 μg/kg, 42061‐33‐6, Sigma, St. Louis, MO, USA) dissolved in the vehicle 24 hours before the surgery and immediately after surgery.…”

Exposure to alcohol during adolescence exerts long-term effects on stress response and the adult brain stress circuits

“…Recently, Jasnic et al (2013) found direct evidence of the role of Avp in regulating pituitary adrenocorticotropic hormone secretion which correlated with CORT concentration in male Wistar rats. This result supports our finding that exposure to alcohol during adolescence decreases the ability of the brain to mount a stress response to an acute stressor in adulthood and this is likely due to the hypothalamic blunting of Avp which consequently decreases the adrenal release of CORT into circulation.…”

Distinct vasopressin content in the hypothalamic supraoptic and paraventricular nucleus of rats exposed to low and high ambient temperature

“…Judging by the circulating ACTH content, our previous results showed not only that both cold and heat stress activate the HPA axis (Djordjevic et al, 2003;Jasnic et al, 2012), but also that AVP plays an important role in potentiating thermal stressor induced secretion of this pituitary hormone (Jasnic et al, 2013(Jasnic et al, , 2010. Driven by these findings, we decided to measure the AVP levels in the hypothalamus of rats exposed either to cold or heat (Fig.…”

“…This indeed constitutes the main pathway of the AVP action on water retention under both resting and stressful conditions. However, the magnocellular originating AVP may also act as secretagogue for ACTH, reaching the anterior pituitary via at least two vascular pathways (Engelmann et al, 2004;Jasnic et al, 2013). Thus, during the stress conditions, AVP is released from axon terminals of the PP into short portal vessels, which connect the anterior and posterior pituitary.…”

“…Furthermore, it is proposed that AVP secreted during stress (e.g. osmotic stress due to heat provoked dehydration) from the PP into the general blood circulation could also reach the corticotrophs (Engelmann et al, 2004;Jasnic et al, 2013), although the physiological relevancy of quantity released through suggested pathway is still under question (Plotsky, 1991).…”