Experimental data concerning the role of serotonin (5-HT) in the control of gonadotropins secretion remain controversial: different receptors subtypes should mediate the serotoninergic action. In the present work we analyzed in prepubertal and adult male rats the FSH and LH responses after administration of the following drugs: 5-hydroxy-L-tryptophan (5-HTP), precursor of 5-HT synthesis, the 5-HT1 receptor agonist 8-hydroxy-2-(di-n-propylamino) tetralin (8-OH-DPAT), the 5-HT2 receptor agonists alpha-methylserotonin maleate (alpha-CH3-HT) and (+/-)-DOI hydrochloride (DOI), the 5-HT3 agonists, quipazine-N-methyldimaleate (QUIP), 2 methyl-serotonin maleate (2-CH3-HT), trimethylserotonin iodide (5-HTQ) and 1-phenylbiguanide (PHE). We found that: a) FSH secretion in adult males was stimulated by 5-HTP, inhibited by 5-HT2 agonists and unaffected by 5-HT3 agonists; b) LH secretion in adult males was stimulated by 5-HTP and alpha-CH3-HT, while DOI and 5-HT3 agonists were ineffective; c) in prepubertal males, 5-HT2 and 5-HT3 agonists inhibited LH release. All these results taken together suggest that: (1) 5-HT2 and 5-HT3 receptors are involved in the control of gonadotropin secretion; (2) FSH and LH secretion are differently modulated by agonists of 5-HT2 and 5-HT3 receptors; (3) the 5-HT2 agonists alpha-CH3-HT and DOI elicit different responses; and (4) the responses obtained vary with animal age, since the inhibitory effect of 5-HT2 and 5-HT3 agonists on LH secretion was observed only in prepubertal males.