Antipsychotic Drugs Inhibit Prolactin Release from Rat Anterior Pituitary Cells in Culture by a Mechanism Not Involving the Dopamine Receptor*

Abstract

Bromocriptine, a dopamine agonist, inhibited secretion of PRL and did not affect GH release from rat anterior pituitary cells in culture. The reversal of this inhibition of PRL release by butaclamol, a dopamine antagonist, was stereospecific; 10 nM d-butaclamol completely reversed the inhibition caused by 10 nM bromocriptine, while l-butaclamol had no effect at concentrations up to 10 JUM. However, both enantiomers at 10 μM inhibited PRL release to 30% and GH release to 91% of control values. Two other dopamine antagonists also inhibited hormone release. Haloperidol (10 μM) inhibited PRL release to 23% of control values and did not affect GH release; 3.3 μM pimozide inhibited PRL and GH release to 18% and 38% of control values, respectively. These data indicate that.the inhibition of PRL by antipsychotic drugs is not mediated through the dopamine receptor.