Endocrine Abstracts

The endocannabinoid system is involved in several homeostatic and neuroendocrine functions. In the present study, we evaluated the effects of type 1 cannabinoid (CB1) receptor antagonist, rimonabant (10 mg/kg, p.o.), on hormone secretion, neuronal activation and mRNA expression in the hypothalamus following isotonic (I−) or hypertonic (H−) blood volume expansion (BVE). Our results showed that the secretion of both oxytocin (OT) and vasopressin (AVP) were increased in response to H-BVE. Both I- and H-BVE stimulated oxytocinergic neuronal activation in the PVN and SON, although vasopressinergic cells were only activated in response to H-BVE. Accordingly, increased expression of both AVP and OT mRNAs were found in these nuclei following H-BVE. Pretreatment with rimonabant significantly potentiated hormone secretion and also vasopressinergic and oxytocinergic neuronal activation induced by BVE, although a decreased AVP and OT mRNA expression was found in the hypothalami of rimonabant pretreated groups. Taken together, these results suggest that the CB1 receptor may modulate several events that contribute to the development of appropriate responses to increased fluid volume and osmolality.