The neurobiological activity of Parawixin 10, isolated from Parawixia bistriata spider venom, was investigated. Cannulas were implanted in the lateral ventricles of Wistar rats (200-250 g, n=6-8 per group) to perform anticonvulsant and behavioral assays, and synaptosomes from cerebral cortices of male Wistar rats were used for neurochemical studies. The results indicate that pretreatment with Parawixin 10 prevents the onset of seizures induced with kainic acid, N-methyl-D-aspartate, and pentylenetetrazole in a dose-response manner. Lower doses of Parawixin 10 significantly increased the latency to onset of kainic acid-, pentylenetetrazole-, and N-methyl-D-aspartate-induced seizures. There were maximum increases of 79% in L-[(3)H]glutamine uptake and 40% in [(3)H]glycine uptake; [(3)H]GABA uptake did not change. The findings demonstrate that this novel compound from P. bistriata venom exerts a pharmacological effect on the glutamatergic and glycinergic systems.