Pregnant rats were exposed to hydrocortisone in a dose of 10 mg/kg on days 9-11 or days 13-15 of gestation. The offsprings born to these mothers were observed for their behavioral development and the response to kainic acid during the infantile period. The response to kainic acid was assessed by the frequency of wet-dog shakes behavior and limbic seizures. 2. The growth rate in the infantile offspring of the 13-15dHc-F1 group showed a slight but significant decrease. 3. All the 13-15dHc-F1 rats exhibited the rearing activity in an open-field at 17 days of age, earlier than in the controls. 4. The ambulatory activity in the 9-11dHc-F1 rats showed a significant decrease at 15 and 17 days of age, whereas no change was shown in the 9-11dHc-F1 rats. 5. The frequency of the wet-dog shakes during the 60 minutes observation after the s.c. injection of 9 mg/kg kainic acid was significantly low in both the 9-11dHc-F1 and 13-15dHc-F1 groups as compared with that in the controls when tested at 25 days of age. The decrease in the response to kainic acid was slightly greater in the 9-11dHC-F1 rats. 6. The frequency of seizures with forelimb clonus and rearing during the 60 minutes observation in the 13-15dHc-F1 was less than that in the controls, whereas no significant difference in the frequency of seizures between the 9-11dHc-F1 and paired control groups was noted. 7. The second generation rats raised from the 9-11dHc-F1 rats by brother-sister mating showed a decrease in the frequency in the kainic acid-induced wet-dog shakes as shown in the F1 offspring. No change in the response to kainic acid was shown in the 13-15dHc-F2 rats.
