Effects of testosterone propionate upon habit-reversals and one-trial learning by castrated white rats.

Abstract

32 male white rats, littermates from mothers of same strain, started to learn 20 habit-reversal problems at 50 days of age in an E-maze for water by the noncorrectional method. They were divided into 3 groups. Two groups of 11 each had been castrated at 32 days of age, and a group of 10 served as control. One castrated group received daily injections of testosterone propionate at 1 mg per kg of body weight 11 days after surgery. The other castrated group and the normal controls received saline. A week of preliminary training accustomed the animals to the daily routine of injection, about 30 min. before being put in the drinking box of a straight alley which they ran for water during the last 2 days. In maze learning proper, after a rat made 9 correct choices on 10 daily trials, the goal was reversed for the next problem. Early in learning, there were some fluctuations in performance, but throughout the rest of the experiment, the castrated-saline group was consistently and significantly inferior to the normals, testifying to the detrimental effect of castration upon adaptive ability in learning successive reversal problems. The fact that the castrated-testosterone group was far superior to the castrated-saline group and exhibited no significant difference from the normal-saline group shows unequivocally that testosterone propionate has a therapeutic property of raising the learning ability of the retarded, castrated white rats to a normal level. A theory is suggested.