OPPOSITE MODULATORY EFFECTS OF OVARIAN HORMONES ON RAT-BRAIN DOPAMINEAND SEROTONIN TRANSPORTERS

The present study was designed to investigate the modulatory effect of gonadal steroids on brain dopamine (DA) and serotonin (5-HT) presynap tic transporters in female and male rats. Female and male rats were ca strated and treated with either vehicle or gonadal hormones. The pharm acodynamic characteristics of the DA and 5-HT transporters were analyz ed by [H-3]BTCP and [H-3]imipramine binding respectively. Ovariectomy (OVX) resulted in an upregulation of the striatal DA transporter and t his alteration was prevented by estradiol (E-2) or E-2 + progesterone (P) treatment but not by P alone. In contrast to the DA transporter, t he hypothalamic 5-HT transporter was down-regulated by OVX in female r ats and this decrease was reversed by the administration of E,, P or t heir combination. The striatal DA transporter and the hypothalamic 5-H T transporter in male rat were not affected by orchidectomy or by admi nistration of testicular hormone. Our findings indicate that ovarian, but not testicular, steroid hormones may play an important role in the regulation of brain DA and 5-HT transporters. It appears that ovarian hormones modulate rat brain 5-HT and DA transporters in opposite dire ctions. These interactions between ovarian steroids and presynaptic tr ansporters may be relevant to DA- and 5-HT-related neuropsychiatric di sorders.