Serum Estradiol Levels and Ethanol-Induced Aggression

Abstract

HILAKIVI-CLARKE, L., M. RAYGADA AND E. CHO. Serum estradiol levels and ethanol-induced aggression. PHARMACOL BIOCHEM BEHAV 58(3) 785–791, 1997.—The biological mechanisms behind ethanol-induced aggression are not known. Because gonadal hormones are linked both to aggression and ethanol, the present study examined relationships among the levels of serum estradiol (E 2), testosterone (T), and aggressive behavior in ethanol-treated male mice. We found that among group-housed male mice, serum E 2 levels were significantly elevated 30 min after a single injection of 0.6 g/kg ethanol. Serum T levels showed a nonsignificant decrease by ethanol. The E 2/T ratio, an index of aromatization of T to E 2, was significantly higher in the ethanol-treated animals when compared with the vehicle-treated animals. We also determined aggressive behavior in the resident-intruder test among isolated male mice at baseline (after a vehicle), and after an injection of 0.6 g/kg ethanol. The mice were grouped accordingly to those that increased, decreased, or remained nonaggressive in response to ethanol administration. We found that at baseline, neither serum T or E 2 levels, nor E 2/T ratio differed significantly between the increased or reduced aggressor mice. In contrast to the increase in serum E 2 levels seen in the nonaggressive mice, ethanol significantly reduced circulating E 2 levels, but did not affect aromatization of E 2 from T in the mice that became aggressive following an ethanol injection. These data suggest that mice who exhibit a paradoxical decrease in serum E 2 levels by ethanol may be particularly prone to ethanol-induced aggression.