EFFECT OF APOMORPHINE PLUS 5-HYDROXYTRYPTOPHAN ON PLASMA PROLACTIN LEVELS IN MALE RATS

  • 1 January 1976
    • journal article
    • research article
    • Vol. 2  (3) , 189-198
Abstract
The relative potency of dopaminergic inhibition and serotonergic stimulation of prolactin secretion in male rats was compared. 5-Hydroxytryptophan (5-HTP), 100 mg/kg, i.p., the precursor of serotonin, produced a 6- to 11-fold increase in plasma prolactin. Apomorphine, a dopamine agonist, at doses of 1-10 mg/kg, i.p., had no significant effect on plasma prolactin. When apomorphine was given with or before 5-HTP it nearly completely blocked the increase in prolactin produced by 5-HTP. Inhibition of prolactin secretion by dopaminergic stimulation appeared to overcome the prolactin releasing effect of serotonin. The results are consistent with the hypothesis that prolactin secretion is ordinarily under a weak serotonergic stimulation and a profound dopaminergic inhibition. Apomorphine might affect plasma prolactin levels by increasing prolactin clearance.