SEX-DIFFERENCES IN ESTRADIOL-INDUCED PROGESTIN RECEPTOR IMMUNOREACTIVITY IN THE GUINEA-PIG PREOPTIC AREA AND HYPOTHALAMUS

Progesterone exerts on the central nervous system a number of effects, some of which are estrogen dependent mostly in the preoptic area and the mediobasal hypothalamus. In these regions, an immunocytochemical s tudy was used to evaluate differences in progesterone receptor (PR) im munoreactivity between the male and the female guinea pig in response to 10 mu g/day estradiol benzoate (EB) for 5 consecutive days. Compare d to EB-treated females, EB-treated males showed a slightly lower numb er of PR-immunoreactive cells in the preoptic area whereas PR-immunore activity appeared in more cells in the anterior part of the ventrolate ral nucleus. The numbers of PR-immunoreactive cells in the arcuate nuc leus did not differ significantly between males and females. These res ults show that regionally localized sex differences exist in the induc ed PR system after 5 days exposure to EB. (C) 1997 Elsevier Science Ir eland Ltd.