The behavioral and toxicological effects of testosterone pellet implantation

Forty gonadally intact male Wistar rats, 200-225 g, were utilized to study the behavioral and physiological effects of testosterone (T) pellet administration. T was administered via pellets (10, 25, 50, and 100 mg) implanted subcutaneously in the dorsal region of the neck. Fifty mg lactate pellets were utilized as the control. T plasma levels were determined using RIA procedures on days 30, 60, and 90 after pellet implantation. T (50 and 100 mg) resulted in plasma concentrations significantly greater than controls. T (100 mg) and lactate control groups were subjected to a competition situation utilizing an estrogen-primed female as the goal object. Subjects were exposed to the test procedure prior to the implantation of the pellets. T resulted in previously defined losers becoming winners in the competition situation on days 30, 60, and 90 post-implantation. T implantation did not significantly affect muricidal behavior as compared to lactate controls. On day 90, the subjects were sacrificed, and the organ/body-weight ratios determined for the heart, liver, testes, and skeletal muscles of the left shoulder girdle. T (100 mg) resulted in a decrease in the testes/body-weight ratio as compared to controls, while the liver/body-weight ratio was increased in this group T (100 mg) also resulted in an increase in the activity of serum enzyme glutamic-oxaloacetic transaminase (SGOT) on day 90 post-implantation. Food intake and body weight were monitored throughout the course of the study. However, no significant differences from controls were noted.