Acquisition of an active avoidance reaction in rats and morphological changes in the hippocampus in pentylenetetrazol kindling.

The relationship between measures of active avoidance behavior and morphological changes in the hippocampus was studied in rats after kindling induced by administration of pentylenetetrazol. Pentylenetetrazol kindling impaired the acquisition of the avoidance reaction and increased the number of intersignal reactions without altering the acquisition of the avoidance reaction in the shuttle box in rats. The numbers of neurons in the hippocampus (fields CA1 and CA3) and dentate fascia decreased, while the numbers of damaged neurons increased. Inverse correlations between seizure severity and the numbers of neurons in hippocampal fields CA1 and CA3 and the dentate fascia were seen in rats subjected to kindling. Rats of this group also showed positive correlations between seizure severity and the numbers of damaged neurons in field CA1 and the dentate fascia. There were no correlations between measures of convulsive activity or the number of cells in hippocampal zones and measures of the acquired avoidance behavior. Control animals showed negative correlations between the numbers of damaged cells in field CA1 and the dentate fascia and the characteristics of avoidance behavior in the first and third training sessions.