IMMUNONEUTRALIZATION OF BETA-ENDORPHIN BLOCKS PROLACTIN-RELEASE DURING SUCKLING WITHOUT AFFECTING TUBEROINFUNDIBULAR DOPAMINERGIC NEURAL ACTIVITY

The effect of immunoneutralization of beta-endorphin on the suckling-i nduced prolactin increase and on the activity of the tuberoinfundibula r dopaminergic (TIDA) neurons was determined in lactating female rats between days 8 - 12 post-partum. Two antisera were used in the immunon eutralization studies. Both were specific for beta-endorphin, exhibiti ng little cross reactivity with met-or leu-enkephalin or dynorphin. An tisera to beta-endorphin completely abolished the suckling-induced pro lactin increase indicating that this endogenous opioid peptide is invo lved in this response. Suckling significantly inhibited DOPA accumulat ion in the median eminence and antiserum to beta-endorphin did not pre vent this inhibition. Additionally, beta-endorphin antiserum significa ntly reduced TIDA neural activity even in pup-deprived dams. These res ults indicate that beta-endorphin is involved in the prolactin secreto ry response to suckling but that inhibition of TIDA neuronal activity is not its mechanism of action. Other possible mechanisms are discusse d.