EFFECTS OF APORPHINE ISOMERS ON RAT PROLACTIN

S(+)-aporphines are partial agonists at D-2 dopamine receptors. High selectivity of anti-dopaminergic action in limbic vs. extrapyramidal regions of rat brain and lack of induction of dopaminergic supersensitivity have suggested their potential as atypical antipsychotic drugs. Now, in testing for effects on circulating prolactin, a typical D-2 antagonist haloperidol elevated, and potent agonist R(-)-11-hydroxy-N-propylnoraporphine lowered, serum prolactin levels in gentled male rats, while S(+)-N-propylnorapomorphine and its 11-monohydroxy analog had little or no effect, even at high doses. Lack of hyperprolactinemia adds to characteristics of S(+)-aporphines that are desirable in improved antipsychotics.