GONADAL-HORMONES AND PICROTOXIN-INDUCED CONVULSIONS IN MALE AND FEMALE RATS

The sensitivity to the GABA-blocking agent picrotoxin was studied in y oung and adult male and female rats, in rats treated with gonadal horm ones and in gonadectomized male and female rats. Picrotoxin was equipo tent in producing convulsions in male and female 20-day-old rats. Adul t females tended to be more, while adult males were considerably less sensitive to picrotoxin than young rats. Picrotoxin was equipotent in displacing t-[H-3]butylbicycloorthobenzoate ([H-3]TBOB) binding to cru de cortical and cerebellar membranes from male and female rat brain. C hronic treatment of male rats, beginning with 30 days of age, with est radiol benzoate enhanced their sensitivity to picrotoxin, while an ana logous treatment of female mts with testosterone propionate was ineffe ctive. Thirty days following castration adult male rats had shorter la tencies to the appearance of picrotoxin-induced convulsions and a high er incidence of death. Ovariectomy in females failed to modify the sen sitivity to picrotoxin. The results suggest that gonadal hormones have a crucial role in the development of sex related differences in the r esponse of rats to picrotoxin and presumably to other GABA-related dru gs. When developed, the male type of reactivity appears to depend more , and the female type less on the presence of circulating hormones in the blood.