ANTAGONISM OF L-STEPHOLIDINE AGAINST BROMOCRIPTINE-INHIBITION ON PROLACTIN LEVEL IN LACTATIONAL RATS

AIM: To study the antagonism of l-stepholidine (SPD) against bromocrip tine (Bro)-inhibition on prolactin (PRL) level. METHODS: Bro (0.5 mg . kg(-1) . d(-1), sc) reduced the PRL and caused a dysplasia of mammary gland in lactational rats. The weight growing of newborn rats was ret arded. The PRL of the lactational rats was assessed by immunoradiometr ic assay (IRMA); the weight of newborn rats and development of mammary glands in lactational rats were also examined. Antagonism of SPD was evaluated. RESULTS: SPD (30 & 100 mg . kg(-1) . d(-1), ip) obviously a ntagonized the Bro that induced lowering the PRL level in lactational rats, the PRL was 11+/-4 & 23 +/- 6 mu g . L(-1) (NS 7 +/- 2) respecti vely on d 15 of postpartum and the development of mammary gland in lac tational rats was normal. The newborn rats grew rapidly in 11-15 d. CO NCLUSION: SPD possessed an antagonism with Bro inhibition on D-2 recep tors located in the pituitary gland, and was an antagonist of dopamine D-2 receptors.