Lack of effect of opiates on release of vasopressin from isolated rat neurohypophysis.

Electrical stimulation of rat neurohypophysis in vitro results in a 150-fold increase in release of vasopressin. Incubation of the isolated lobes with endogenous opiates (Met-enkephalin, Leu-enkephalin, beta-endorphin), morphine or naloxone did not change the evoked release of vasopressin significantly. The results obtained do not confirm the hypothesis that endogenous opiates inhibit the release of vasopressin from this preparation.