ETHANOL AND THE INHIBITION OF OXYTOCIN RELEASE IN LACTATING RATS

Abstract

ABSTRACT The effect of ethanol on the release of oxytocin in the rat was studied using suckling as the oxytocin releasing stimulus. Milk removal on 30 min suckling by a litter of 8 after 18 h separation from the mother on postpartum day 13–16 was used as a parameter of oxytocin liberation. Under these conditions 25 mU intravenously injected oxytocin permitted normal milk removal in anaesthetized rats, whereas after injection of 10 mU oxytocin only about half of the normal milk yield was obtained. Ethanol in doses varying from 1.0 to 5.0 g/kg was injected intraperitoneally into the dam as 10 to 20 % solution in saline 30 to 60 min before nursing commenced and the milk yield was compared with saline injected control rats. At the dose level of 1.0 g/kg ethanol had no effect on milk removal but 2.0 g/kg caused a significant reduction to about 60 % of normal, and with higher doses a further reduction of the milk yield occurred. At 3.5 g/kg about 14% of normal milk yield was obtained, and at 5.0 g/kg a complete inhibition of milk ejection was observed. Oxytocin administration permitted normal milk removal in all ethanol treated rats indicating that there was no peripheral effect on the mammary gland. The experiments suggest that ethanol inhibits oxytocin release also in the rat.