Effects of sleep deprivation on serum testosterone concentrations in the rat

Sleep deprivation (SD) leads to decreases in circulating levels of testosterone with unknown mechanisms. We tested the hypothesis that decreased testosterone levels associated with SD may be caused by serotonin-mediated inhibition of its production. Male rats were subjected to SD for 24 or 48 h using the dish-over-water-method with a Rechtschaffen apparatus. Serum testosterone, corticosterone and serotonin (5-HT) concentrations were assessed thereafter, as were testicular StAR and 5-HT 2 receptor levels. SD, regardless of duration led to significant decreases in serum testosterone levels and testicular steroid acute regulatory protein (StAR) protein expression, while 5-HT levels were significantly elevated (all P<0.05). Corticosterone concentrations were significantly increased in 48 h SD rats (P<0.05). In primary Leydig cell cultures, 5-HT decreased chorionic gonadotropin-induced testosterone secretion and StAR expression, which appeared to be dependent on 5-HT 2 receptor activation but independent of cyclic AMP signaling. These findings suggest that decreased serum testosterone levels in SD rats may be the result of 5-HT-related inhibition of testosterone production and decreased testicular expression of StAR protein.