SEXUAL DIFFERENCES IN THE EFFECT OF THE GABAERGIC SYSTEM ON LH-SECRETION AND IN THE HYPOTHALAMIC ONTOGENY OF GABA(A) RECEPTORS IN PREPUBERTAL RATS

The administration of aminooxyacetic acid (AOAA), which increases hypothalamic GABA concentrations, induced a significant increase in LH levels in female rats of 12, 16 and 18 days of age. This stimulatory effect of AOAA on serum LH levels was not observed at 21 and 25 days of age whereas a significant decrease in the LH concentrations by AOAA was found at 30 days of age. The neonatal androgenization of female rats abolished the effects of AOAA and no effects of AOAA were found in male rats at the different ages studied. The muscimol binding sites in medial basal and preoptic anterior hypothalamic areas showed a significant different sexual ontogenic pattern. Males rats castrated at birth showed a a very similar ontogenic pattern of [H-3]muscimol binding sites to female rats and significantly different to male control rats. It is concluded that there are sexual differences in the effect of GABAergic system on LHRH-LH secretion and in the development of hypothalamic GABA(A) receptors during sexual maturation. These differences are probably connected with the neonatal exposure to androgens that would induced changes in the composition and probably in the properties of GABA(A) receptor that in turn modified its effects on LHRH neurons.