Gonadectomy reduces the density of androgen receptor-immunoreactive neurons in male rat's hippocampus: Testosterone replacement compensates it

Abstract

Background: In the present study, the role of gonadectomy on memory impairment and the density of androgen receptor-immunoreactive neurons in rats' hippocampus as well as the ability of testosterone to compensate of memory and the density of androgen receptors in the hippocampus was evaluated. Methods: Adult male rats (except intact-no testosterone group) were bilaterally castrated, and behavioral tests performed 2weeks later. Animals bilaterally cannulated into lateral ventricles and then received testosterone (10, 40 and 120μg/0.5μl DMSO) or vehicle (DMSO; 0.5μl) for gonadectomized-vehicle group, 30min before training in water maze test. The androgen receptor-immunoreactive neurons were detected by immunohistochemical technique in the hippocampal areas. Results: In the gonadectomized male rats, a memory deficit was found in Morris water maze test on test day (5th day) after DMSO administration. Gonadectomy decreased density of androgen receptor-immunoreactive neurons in the rats' hippocampus. The treatment with testosterone daily for 5days attenuated memory deficits induced by gonadectomy. Testosterone also significantly increased the density of androgen receptor-immunoreactive neurons in the hippocampal areas. The intermediate dose of this hormone (40μg) appeared to have a significant effect on spatial memory and the density of androgen receptor-immunoreactive neurons in gonadectomized rats' hippocampus. Conclusions: The present study suggests that testosterone can compensate memory failure in gonadectomized rats. Also testosterone replacement can compensate the reduction of androgen receptor-immunoreactive neurons density in the rats' hippocampus after gonadectomy.