GABAergic and Serotoninergic systems on Hypothalamic Catecholamines

OBJECTIVES: The aim of the present investigation was to determine whether the catecholaminergic system is involved in gabaergic and serotoninergic effects on gonadotrophin secretion during sexual development. To this end, we studied the effect of GABAergic and serotoninergic systems on hypothalamic catecholamine content at different stages of sexual development. METHODS: The effect of GABA A and GABA B agonists and 5-hydroxy-L-tryptophan on hypothalamic noradrenaline and dopamine content were determined in prepubertal (16 days old) and peripubertal (30 days old) rats. RESULTS: At 16 days of age GABA agonists did not modify hypothalamic noradrenaline content, whereas a signifi cant decrease in catecholamine concentration was observed in peripubertal rats at 30 days of age. Similar changes were observed with GABA agonists administration on dopamine hypothalamic levels, i.e no effects at 15 days of age and a signifi cant decrease at 30 days. The administration of 5-hydroxy-l-tryptophan (5-HTP) induced a decrease of hypothalamic concentration of noradrenaline and dopamine at both ages. CONCLUSION: Results indicate that the GABAergic system modifi es the hypothalamic catecholamine content in peripubertal but not in prepubertal rats while serotonin has an inhibitory effect at both stages of sexual maturation. Even though both systems induce similar ontogenic modifi cations on the gonadotrophin axis (stimulatory effect in prepubertal and inhibitory action in peripubertal and adult rats) the present results appear to indicate that GABAergic and serotoninergic systems regulate gonadotrophin secretion by different hypothalamic mechanisms. * Established Investigator. National Research Council. Buenos Aires Argentina O R I G I N A L A R T I C L E