SEX-DIFFERENCES IN EEG IN ADULT GONADECTOMIZED RATS BEFORE AND AFTER HORMONAL TREATMENT

EEG activity was recorded from the left and right parietal cortex in a dult male and female Wistar rats that were gonadectomized (GNX) after puberty during 2 days without and 3 days with hormonal treatment (eith er testosterone propionate, 5 alpha-DHT or vehicle in males and proges terone, estradiol benzoate or vehicle in females). In contrast to EEG characteristics reported for intact rats, GNX abolished right over lef t parietal activation in both sexes and, sex differences in EEG interh emispheric. correlation and in theta and delta relative power in the r ight parietal; additionally GNX males showed higher absolute power tha n females. Hormonal treatment reestablished interparietal asymmetry in both sexes and a lack of sex differences in absolute power, however, it was not enough to reestablish sex differences in delta and theta pr oportion in the right parietal nor in interhemispheric correlation. Di fferential effects were obtained with testosterone propionate and 5 al pha-DHT in males suggesting that activational effects of testosterone on EEG are probably exerted through testosterone or its aromatized met abolites. The results of our study indicate that the activational effe cts of gonadal steroids after puberty are necessary for maintaining se x differences in the EEG of the adult rat. (C) 1997 Elsevier Science L td. All rights reserved.