it is established that androgen modulates various neurotransmitters in the CNS. Testosterone decreases γ-aminobutyric acid concentration in the hypothalamus, which is blocked by flutamide, a testosterone receptor blocker (14, 15). Testosterone, probably by its conversion to estradiol, increases serotonin transporter mRNA expression in dorsal raphe nucleus (16), and it also increases the density of 5-hydroxytryptamine receptors and serotonin transporter sites in the forebrain (3, 16) of castrated male rats.