The effects of maternal exposure during the first 10 days of lactation to picrotoxin (0.75 mg/kg sc) on maternal behavior, offspring physical and neurobehavioral development as well as sexual behavior were studied. Results showed that (1) dam food and water consumption, maternal behavior and body weight were not different between control and experimental animals, (2) male and female pup body weight and the development of physical landmarks did no differ between control and experimental groups, (3) negative geotaxis was improved in female experimental offspring and palmar grasp reflex did not differ between groups, (4) at 75 days of age the square crossing by female rats of the experimental group was increased in relation to the control group; no differences were observed between male control and experimental animals, (5) male experimental rats exhibited a significant increase in the number of mounts, intromissions and ejaculations parallel to a decrease in latency to first mount, intromissions and ejaculation as well as in the latencies of first postejaculatory mount and intromission and (6) the intromission frequency per minute (hit rate) was increased in these animals. These results suggest that postnatal exposure to picrotoxin improved the sexual behavior of rats. Three hypotheses were proposed to explain the mechanisms underlying this effect: (1) the development of subsensitivity of GABAergic receptors, (2) an interference with early receptor development or (3) with neurotransmitter balance, mainly involving the dopaminergic system.