Failure to find sex differences in testosterone activated aggression in two strains of rats

The effect of testosterone (testosterone propionate: TP) on intraspecific aggression in males and females of two strains of rats—WEzob and S3—was examined. Pairs of these rats, gonadectomized and treated either with oil or with testosterone propionate (TP), were tested in three different combinations: OIL against OIL, OIL against TP, and TP against TP-treated animals. Subsequently the effects of TP treatment of the subject and for the opponents interaction with sex and strain on the occurrence of diverse social + aggression behavioral parameters were determined. The results of the S3 strain indicate that testosterone treatment of either the subject or the opponent stimulates aggression in both males and females. No sex difference could be determined with respect to the incidence of aggression. In the WEzob strain a stimulatory effect of TP was shown in females but not in males. The absence of a clear stimulatory effect of TP in WEzob males in terms of changes in the total time spent on aggression, however, could wrongly suggest that TP does not affect aggression in these animals. The possibility of TP having an effect on these males in terms of increasing the intensity of fighting is discussed.