Hypothalamic and neurohypophysial vasopressin and oxytocin in melatonin-treated pinealectomized male rats.

The effect of melatonin on hypothalamic and neurohypophysial vasopressin and oxytocin was investigated in normal and pinealectomized rats. Pinealectomy was followed by a decrease of both vasopressin and oxytocin content in the hypothalamus and neurohypophysis. In unpinealectomized rats, melatonin decreased vasopressin and oxytocin storage in the hypothalamo-neurohypophysial system. Following pineal removal, melatonin did not augment the pinealectomy-induced decrease of vasopressin and oxytocin in the neurohypophysis; the hypothalamic storage of both neurohormones was even higher when compared with vehicle-treated animals.