The type-1 cannabinoid receptor modulates the hydroelectrolytic balance independently of the energy homeostasis during salt load

F.M.V. Vechiato^a,P.M.S. Rivas^a,S.G. Ruginsk^a,b,B.C. Borges^a,L.L.K. Elias^a,J. Antunes-Rodrigues^{a, ,}

Abstract

Hydroelectrolytic imbalances, such as saline load (SL), trigger behavioral and neuroendocrine responses, such as thirst, hypophagia,vasopressin(AVP) andoxytocin(OT) release andhypothalamus–pituitary–adrenal (HPA) axis activation. To investigate the participation of the type-1cannabinoid receptor(CB1R) in these homeostatic mechanisms, male adult Wistar rats were subjected to SL (0.3 M NaCl) for four days. SL induced not only increases in the water intake and plasma levels of AVP, OT andcorticosterone, as previously described, but also increases inCB1Rexpression in thelamina terminalis, which integrates sensory afferents, as well as in the hypothalamus, the main integrative and effector area controlling hydroelectrolytichomeostasis. A more detailed analysis revealed that CB1R-positive terminals are in close apposition with not onlyaxonsbut also dendrites and secretory granules of magnocellular neurons, particularly vasopressinergic cells. In satiated and euhydrated animals, the intracerebroventricular administration of the CB1Rselective agonistACEA(0.1 μg/5 μL) promotedhyperphagia, but this treatment did not reverse the hyperosmolality-induced hypophagia in the SL group. Furthermore, ACEA pretreatment potentiated water intake in the SL animals during rehydration as well as enhanced the corticosterone release and prevented the increase in AVP and OT secretion induced by SL. The same parameters were not changed by ACEA in the animals whose daily food intake was matched to that of the SL group (Pair-Fed). These data indicate that CB1Rs modulate the hydroelectrolytic balance independently of the food intake during sustained hyperosmolality andhypovolemia.

Hormones and Behavior

Volume 78, February 2016, Pages 43–51