Serum estradiol levels and ethanol-induced aggression

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. (C) 1997 Elsevier Science Inc.