Female Wistar rats were exposed to a subconvulsant dose of picrotoxin (0.75 mg/kg, sc) on day 18 of pregnancy, immediately after parturition and daily during the first 5 days of lactation. In adulthood, the offspring were tested in an open-field, in an elevated plus maze and for social interaction. Results showed increased locomotor activity (75 days of age) and decreased social interaction (90 days of age) in experimental male rats compared to control male rats. No effects on behaviors related to anxiety were observed in males or females tested in the plus maze apparatus. An additional comparison of the activity of male and female animals perinatally treated with picrotoxin showed a lack of the classical sexual dimorphic responses in the open-field (control male = 68.7 +/- 6.31; control female = 98.4 +/- 6.31; experimental male = 89.6 +/- 6.32; experimental female = 113.2 +/- 4.74). We suggest that perinatal picrotoxin exposure may interfere with normal male masculinization rather than increasing anxiety in male rats.