STUDIES ON THE DEVELOPMENT OF HYPOTHALAMIC REGULATION OF THE HYPOPHYSEAL GONADOTROPIC ACTIVITY IN RATS

  • 1 January 1980
    • journal article
    • research article
    • Vol. 69  (1) , 1-16
Abstract
Development of the hypothalamic regulation of gonadotrophs was studied in rats. Pituitaries of rat fetuses were cut serially at 4 .mu.m in the coronal plane, and every 5th section was mounted and stained immunohistochemically with anti-hCG [human chorionic gonadotropin] serum. Sum total of the numbers of the immunoreactive cells in each section was used as an index of the number of gonadotrophs of the pituitary. Anti-rLH [rat lutropin], and anti-rLH.beta., anti-rFSH [rat follitropin], anti-rTSH [rat thyrotropin] and anti-rTSH.beta. sera were also applied additionally for staining. The anti-hCG serum-positive cells were 1st evident on day 17.5 of gestation, and the cells reacting for anti-rLH and anti-rLH.beta. sera started also to appear. On day 19.5, very few cells appeared to react for anti-rFSH serum. I.p. injection of LHRH [luliberin] to the fetuses induced a remarkable disappearance of the immunoreactive materials, and as a result a numerical reduction occurred in the immunoreactive cells. These phenomena were noted even on day 18.5 of gestation. Encephalectomy of day 16.5 fetuses and daily i.p. injection of anti-LHRH serum to 17.5-19.5 day old fetuses were carried out with the purpose of blocking the effect of endogenous LHRH to fetal pituitary. Dense staining of the cytoplasm and remarkable reduction in size and in number of gonadotrophs were obtained after day 20.5 of gestation in both animal groups. The hypothalamus may start to govern the hypophyseal gonadotrophs on day 20.5 of gestation in rat.