Aging increases the susceptibility to develop anhedonia in male rats.

The objective of this study was to establish the effect of aging on the development of anhedonia, a core feature of depression. Young and old male Wistar rats (of around 3-5 and 12-15 months, respectively) were exposed to a chronic variable stress (CVS) schedule for 3 weeks. CVS produced anhedonia, indicated by a reduction in the intake of a sucrose solution (1%), in 8 out of 23 (35%) young rats and in 19 out of 26 (73%) old rats, implying that old animals are more susceptible to stress and develop anhedonia more readily than young animals. Young and old anhedonic rats showed a similar temporal course in the reduction of sucrose consumption, reaching the anhedonic state after 2 weeks of CVS exposure. Compared with young animals, old rats had lower basal serum testosterone and estradiol levels. The systemic levels of corticosterone did not vary between both age groups. No significant pathological condition was detected in old animals. It is suggested that the higher susceptibility to develop anhedonia in male rats could be associated to neuroendocrine changes consequent to aging.