Lack of effects of anabolic-androgenic steroids on locomotor activity in intact male mice

Anabolic-androgenic steroid abusers have reported hyperactivity, euphoria, and decreased fatigue, among other behavioral effects. It has been suggested that the effects of these substances on the central nervous system are similar to those of psychostimulants; however, the influence of steroids on general locomotor activity in laboratory animals is not well understood, especially how noncastrated male rodents are affected. In this study, spontaneous locomotor activity displayed by gonadally intact male mice submitted to several experimental conditions was analyzed. Different housing conditions (individual or cohabiting with a female), diverse steroids (testosterone propionate, nandrolone decanoate, and a mixture of both steroids) and single or repeated injections were employed. At 24 hours after the injection (after the three last injections in the case of chronic treatment) spontaneous locomotor activity was registered on an activity recorder for one 15-min. period. No effects due to the treatment were found in almost every experimental condition. These results contrast with the dramatic decreases in activity described for female mice after treatment with such steroids. It seems that in intact males the steroids' influence on spontaneous locomotor activity may be more subtle than expected. These effects seem very complex depending on duration of treatment and specific situations (spontaneous or forced activity) as well as the interaction with endogenous androgen levels.