Comparison of the effects of central acting drugs on prolactin release in young and old male rats.

Abstract

AbstractThe effects of several central acting drugs on prolactin (PRL) secretion were compared in young (3-4 months) and old (18-19 months) Sprague-Dawley male rats. Administration of the catecholamine synthesis inhibitor, methyl-DOPA, or the dopamine receptor blocker, haloperidol, produced a significantly greater increase in plasma PRL in the old than in the young rats. Stimulation of the serotonergic system by quipazine or enhancement of opioid activity by morphine produced a significantly greater rise in plasma PRL in the young than in the old male rats. Administration of the specific opiate antagonist, naloxone, reduced plasma PRL levels more in old than in young male rats. but this difference was not significant. Measurement of pituitary content and concentration of PRL revealed that both were significantly greater in old than in young male rats. These results suggest that hypothalamic dopamine continues to be an important inhibitor of PRL release in old male rats, whereas serotonin and the opiates b...