Depression-like behavior and reduced plasma testosterone levels in the senescence-accelerated mouse.

During aging, levels of testosterone gradually decline in men and low levels of testosterone in aged men are accompanied by increased incidence of depressive disorders. The senescence-accelerated-prone mouse 10 (SAMP10) is well known as an animal model of aging. The purpose of this study was to investigate the motor function, anxiety levels, depression-related emotional responses, attentional function and plasma levels of testosterone and dehydroepiandrosterone (DHEA) in SAMP10. SAMP10 exhibited a significant prolongation of immobility time compared to that of the aged-matched control senescence-accelerated-resistant mouse 1 (SAMR1) in the tail suspension test for measuring depression. Moreover, significant low levels of plasma testosterone but not DHEA were found in SAMP10, and the testosterone levels were inversely correlated with the depression-like behavior. By contrast, we did not observe any significant differences between SAMP10 and SAMR1 in the open-field, rota-rod, elevated plus-maze, marble-burying behavior, or prepulse inhibition test. The results of the present study indicate that testosterone may play an important role in the depression-like behavior in SAMP10.