Opioid control of prolactin secretion in late pregnant rats is mediated by tuberoinfundibular dopamine neurons

Abstract

Prolactin (PRL) secretion from the anterior pituitary is tonically inhibited by tuberoinfundibular dopamine (TIDA) neurons in the arcuate nucleus of the hypothalamus. During late pregnancy, TIDA neuronal activity is reduced allowing the expression of an antepartum PRL surge. We show here that continuous infusion of the opioid receptor antagonist naloxone (10 mg/h) during the night preceding parturition completely abolished the antepartum PRL surge and significantly increased TIDA neuronal activity. These data indicate that endogenous opioid neurons facilitate PRL secretion at the end of pregnancy by suppressing TIDA neuronal activity.