Insulin and release of neurohypophysial hormones: in vivo and in vitro studies.

No significant effect of intracerebroventricular administration of insulin on the bioassayed neurohypophysial storage of vasopressin and oxytocin could be found. This finding, however, only indirectly reflects possible changes of vasopressin and oxytocin release. Incubation of neurointermediate lobes in Locke's solution containing 3.3 mumol/l insulin resulted in an inhibition of oxytocin release under resting conditions as well as in a decrease of both vasopressin and oxytocin release during depolarization due to excess potassium. These results seem to suggest a possible regulatory role of brain insulin in the mechanisms of release of neurohypophysial hormones.