ADRENERGIC AND CHOLINERGIC CONTROL OF OXYTOCIN RELEASE EVOKED BY VAGINAL, VAGAL AND MAMMARY STIMULATIONS IN LACTATING RATS

Abstract

The amounts of oxytocin released during Ferguson and vago-pituitary reflexes were estimated by measurements of intramammary pressure. For the milk-ejection reflex, the gain in weight of the young over a period of 30 min was taken as an indirect index of the release of oxytocin. Antagonists of specific cholinoceptors and adrenoceptors were injected into the 3rd ventricle in order to delineate the role of the mediators and receptors in the control of oxytocin release. The results suggest that the 3 reflexes have a specific chemical transmission since: the Ferguson reflex is inhibited by the drugs that only block .alpha.- and .beta.-adrenoceptors; the vago-pituitary reflex is inhibited by the drugs that block .alpha.- and .beta.-adrenoceptors and muscarinic cholinoceptors; and the milk-ejection reflex is inhibited by the drugs that block .alpha.-adrenoceptors and muscarinic and nicotinic cholinoceptors.