Treatment with an anabolic-androgenic steroid affects anxiety-related behavior and alters the sensitivity of cortical GABAA receptors in the rat

Abstract

The putative psychotropic effect of the anabolic-androgenic steroid, testosterone propionate (TP), was determined in intact adult male rats after 1 or 2 weeks of continued exposure via subcutaneously implanted capsules. Behavior was assessed in a novel open-field arena and in the elevated plus-maze. In addition, gamma-aminobutyric acid (GABA)-stimulated 36chloride (Cl-) influx was determined in cerebral cortical synaptoneurosomes as a function of TP exposure. The weight of the prostate gland was taken and blood serum level of total testosterone (T) was assayed. One week of TP exposure (approximately 3.5-5.0 mg/kg per day) resulted in anxiolytic behavior, as evidenced by an increase in the exploration of the open arms of the elevated plus-maze. The behavioral effect in the elevated plus-maze was not observed in animals exposed to TP for a 2-week period. Ambulation scores in the novel open field did not change as a function of TP exposure. Blood T levels were increased 7-fold by 1 week of exposure, and increased 10-fold in animals with implants for a 2-week period. After 1 week of TP exposure, the concentration of GABA that elicited 50% of the maximal Cl- influx in cortical synaptoneurosomes (i.e., EC50) was significantly decreased; this effect was not seen in animals exposed to TP for 2 weeks. The maximal efficacy of the GABAA receptor-gated Cl- influx was not affected after 1 or 2 weeks of TP treatment. Thus, 1 week of treatment with TP resulted in anxiolytic behavior that was accompanied by an increase in the sensitivity of cortical GABAA receptors. However, the behavioral and neurochemical changes were no longer present after 2 weeks of TP exposure. These results are discussed in terms of the agonist effects of reduced androgen metabolites at the GABAA receptor and the possible development of tolerance to these effects.