Oestrogen–bromocriptine interaction in the control of luteinizing hormone and prolactin secretion in the neonatally oestrogenized female rat

Neonatally oestrogenized female rats showed hyperprolactinaemia (prolactin, 230 micrograms/l), normal LH levels and absence of a positive feedback effect of oestrogen on secretion of LH at 5 months of age. Bromocriptine treatment for 13 days (1 mg/kg per day) caused no changes in LH levels and prolactin levels decreased to normal values (33 micrograms/l). This decrease in prolactin concentration was not followed by the recovery of phasic LH response to oestrogens. The effectiveness of oestrogens to induce prolactin secretion was greater in the neonatally oestrogenized rats than in the control group. In both cases the effect diminished after bromocriptine treatment. These results indicate that hyperprolactinaemia is not the cause of the anovulatory state in oestrogenized rats and that neonatal treatment with oestrogens alters oestrogen--prolactin relations, probably involving dopamine.