Studies will continue on the design of synthetic analogs of the neurohypophysial hormones with more potent and specific agonistic and antagonistic activities. These will be exploited in experiments on the physiological and pathological actions of endogenous neurohypophysial peptides. We aslo plan further studies on the influence of opiates and endogenous opioids on the reflex release of oxytocin and vasopressin in the intact animal and in isolated hypothalamoneurohypophysial system.