Gonadectomy impairs T-maze acquisition in adult male rats.

Recent studies have shown that chronic gonadectomy increases the density of dopaminergic axons in prefrontal but not sensorimotor cortices in adult male rats. Since supranormal prefrontal cortical dopamine stimulation is known to impair rats' performance in T-maze delayed alternation paradigms, we tested whether long-term gonadectomy might also impair T-maze performance. For comparison, sensorimotor functions were also assessed. Adult male rats were gonadectomized and placebo-, estradiol-, or testosterone propionate-treated or were sham operated and placebo-treated. Four weeks after surgery, the subjects were tested using a rotorod apparatus and in the acquisition of a T-maze delayed alternation paradigm. Gonadectomized placebo-treated and estradiol-treated rats took significantly longer to acquire the T-maze rule than controls, and gonadectomized, testosterone-treated rats acquired the task within the same time frame as controls. No group differences were detected in rotorod performance. Thus, chronic gonadectomy induced testosterone-sensitive, estradiol-insensitive acquisition deficits in a spatial learning task but had no demonstrable effects on the sensorimotor functions tested.