LONG-TERM TESTOSTERONE OR DIETHYLSTILBESTROL TREATMENT AFFECTS GAMMA-AMINOBUTYRIC-ACID AND CENTRAL-TYPE BENZODIAZEPINE RECEPTORS BUT NOT PERIPHERAL-TYPE BENZODIAZEPINE RECEPTORS IN THE FEMALE RAT-BRAIN

Steroids have often been associated with modulation of the GABAergic s ystem in the central nervous system, mainly in ovariectomized rats. In the present study, the effect of the synthetic estrogen diethylstilbe strol (DES) and testosterone (T) on the density of peripheral and cent ral benzodiazepine (BZ) and gamma-aminobutyric acid (GABA(A)) receptor s was evaluated in the frontoparietal cortex and whole cerebellum of f emale rats during the peripubertal period. The density of peripheral-t ype BZ receptors was not altered in either of these organs, whether or not treated with DES or T. The density of central BZ and GABAA recept ors in either frontoparietal cortex or whole cerebellum was significan tly reduced following treatment with DES or T; however, the effect of DES was much more pronounced. The similarity of the effect of T to tha t of DES may suggest that the effect of T is mediated at least partial ly by intraovarian biosynthesis of estradiol-17beta from the exogenous ly administered T. Collectively, these results may suggest that in fem ale rats during the peripubertal period, sex steroids produce a down-r egulatory effect on expression of the brain GABA(A)/BZ complex, in con trast to their well-established up-regulatory effect in adult ovariect omized rats.