Delayed impairment of response extinction after single seizures induced by picrotoxin.

Male Wistar rats were trained with a food rewarded task and treated with single convulsive dose of picrotoxin. Behavioural test for response extinction by non-reinforcement procedure, which was considered as inhibitory learning, was performed 1, 2, 5, or 7 days after the treatment. The results obtained showed that 5 days after seizures, the animals persisted in performing the task, and extinction procedure was hampered. The resistance to response extinction is evidence of delayed influence on inhibitory processes caused by the single seizures. On the contrary, the response extinction was not deteriorated 1, 2 or 7 days after picrotoxin treatment. It is assumed that delayed disturbances of inhibitory learning could result from the deterioration of hippocampal functioning.