DIFFERENT EFFECTS OF THE SEROTONERGIC AGONISTS BUSPIRONE AND SUMATRIPTAN ON THE POSTERIOR PITUITARY HORMONAL RESPONSES TO HYPOGLYCEMIA IN HUMANS

The responses of serum oxytocin (OT) and vasopressin (AVP) to the sero tonergic HT1A agonist buspirone (15 mg p.o.) or the HTD1 agonist sumat riptan (6 mg injected subcutaneously) were evaluated in 7 normal men e ither in basal conditions or during an insulin (0.15 iu/kg as an i.v. bolus) tolerance test (ITT). Neither buspirone nor sumatriptan adminis tration modified the basal secretion of AVP and OT. Stimulation of 5HT -1D receptors with sumatriptan was unable to change neither AVP nor OT response to insulin-induced hypoglycemia. On the other hand, the pret reatment with the 5HT1A agonist buspirone significantly enhanced the O T response during hypoglycemia, without modifying the AVP rise. The re sults of this study suggest that serotonergic 5HT1A receptors may inte ract with hypoglycemia in the stimulation of OT, but not AVP secretion .