Effects of sleep deprivation on serum testosterone concentrations in the rat

► Sleep deprivation increases serum 5-HT levels. ► Sleep deprivation reduces testicular StAR protein levels. ► 5-HT reduces hCG-induced StAR expression in Leydig cell cultures. ► 5-HT reduces hCG-induced testosterone release in Leydig cell cultures. ► 5-HT2 receptors regulate testosterone release during sleep deprivation.