On steroid noradrenergic system interaction during the hypothalamic differentiation period in the female rat.

Neonatal administration of alpha-methyl-p-tyrosine, alpha-MPT, (1 mg s.c. on days 4 and 5) or 6-hydroxydopamine, 6-OHDA, (100 or 600 micrograms s.c. on day 1) did not produce any change of the reproductive function in female rats. Both drugs were unable to prevent the anovulatory syndrome induced by the administration on day 4 of testosterone propionate, TP, (25 micrograms) or estradiol benzoate, EB, (10 micrograms), but blocked the precocious vaginal opening induced by EB neonatal administration. These data suggested that the complete integrity of noradrenergic system appears to be not necessary for the differentiation of cyclic gonadotropin secretion in the female rat. This system seems to be involved in precocious vaginal opening induced by neonatal EB administration.