Endocrine Abstracts

The endogenous opiates cause a rapid increase in PRL secretion. The present study was designed to investigate the involvement of opioidergic pathway in the regulation of PRL secretion by the endogenous excitatory neurotransmitters in primates. In the first set of experiments saline infusion (3 ml/h) for a period of 3 h was given. In the second set of experiment NMA injections were administered with one hr interval. In the third set of experiment NAL infusion (5 mg/3 ml per h) for 2 h along with a bolus injection of NAL (5 mg/3 ml) for a period of 2 h was given while in the fourth set of experiment two NMA injections (at 30 and 90 min) were given during NAL bolus plus infusion. No significant change in plasma PRL level was observed during saline infusion whereas both NMA injections caused highly significant (P<0.05) increase in plasma PRL level. NAL bolus plus infusion caused highly significant (P<0.001) decrease in PRL level. Both NMA injections given with bolus and infusion of NAL were failed to produce any significant increase in plasma PRL concentrations. The results showed an involvement of opioid peptides in the central regulation of PRL in primates and that endogenous excitatory amino acids act through endogenous opioids for the regulation of PRL from lactotropes of pituitary.