Effects of chronically high doses of the anabolic androgenic steroid, testosterone, on intermale aggression and sexual behavior in male rats.

To determine if chronic exposure to high doses of anabolic androgenic steroids (AAS) increase aggression and sexual activity in gonadally intact rats, we administered SC injections of testosterone propionate (TP: 1 mg) or propylene glycol (PG: as a vehicle control) three times per week for 10 consecutive weeks. Weekly tests for male copulation were conducted by pairing each male with a sexually receptive female in a glass arena and recording various parameters of copulation. Chronic treatment with TP did not alter any parameter of male copulation including ejaculation and post ejaculatory interval. Sexually experienced males were tested once per week for intermale aggression in a neutral environment. For aggression tests, each experimental animal was placed into an arena with an opponent male for 15 min. The opponent, a gonadally intact male, was used only for the purpose of the aggression test. Frequencies of dominance, submissive, threat, and fight postures, as well as approaches were scored for each animal. TP-treated males did not differ in body weight from PG-treated males, suggesting that the increased aggression was not due to increased body mass. The results of this study show that chronic exposure to the anabolic androgenic steroid, testosterone, potentiates male aggressive response patterns but does not alter male sexual behavior or body weight.