Abstract
In men, aging is accompanied by a gradual decline in androgen secretion. Studies suggest beneficial effects of endogenous and exogenous testosterone on affective behavior and cognitive functions. The aim of this study was to describe behavioral and cognitive sex differences and to analyze the effects of long-term androgen deficiency in aged male rats. Thirty-months old rats divided into three groups (males, females and males gonadectomized as young adults) underwent a battery of behavioral tests assessing locomotor activity, anxiety, memory, anhedonia, sociability and depression-like behavior. No major effect of gonadectomy was found in any of the analyzed behavioral measures in male rats. The only consistent sex difference was confirmed in depression-like behavior with longer immobility time observed in males. In an interventional experiment, a single dose of testosterone had no effect on gonadectomized male and female rats in the forced swim test. In contrast to previous studies this comprehensive behavioral phenotyping of aged rats revealed no major role of endogenous testosterone. Based on our results long-term hypogonadism does not alter the behavior of aged male rats, neither does acute testosterone treatment. Whether these findings have any consequences on androgen replacement therapy in aged men remains to be elucidated.
Highlights
Male and female brains differ in their structure and function [1,2,3]
Thirty‐months old rats divided into three groups underwent a battery of behavioral tests assessing locomotor activity, anxiety, memory, anhedonia, sociability and depression‐like behavior
GDX male rats had lower plasma www.aging‐us.com testosterone concentration than control male rats, gonadectomy did not lead to any behavioral differences described in young GDX rats
Summary
Male and female brains differ in their structure and function [1,2,3]. Brain masculinization in male animals in contrast to females was proved in many behavioral characteristics including affective performance and cognitive function. Aging is associated with a decline in sex steroid hormones. The loss of bioavailable androgens during aging increases the risk of dysfunction in androgen responsive tissues including the brain [12]. It was shown, that cognitive and affective performance and social behavior decline in aging [13,14,15]. Whether sex differences in behavior are affected by the agerelated androgen depletion is not clear
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