[Active avoidance learning in rats and morphological changes in the hippocampus after pentylenetetrazole kindling]

The relationship between parameters of active avoidance conditioning and morphological changes in the hippocampus was investigated using pentylenetetrazole kindling animal model of epilepsy. Pentylenetetrazole kindling impaired learning of escape reaction and increased the number of intertrial crossings in a shuttle box during active avoidance conditioning. Kindling decreased the number of neurons in the hippocampal CA1 and CA3 fields and in the dentate gyrus and increased the number of abnormally changed neurons, which displayed cell shrinkage and chromatophilic staining. Negative linear correlations were found between seizure severity and the number of normal neurons in the hippocampus (CA1 and CA3) and dentate gyms in the kindled rats. Positive correlations between the number of damaged neurons and seizure severity were revealed in the CA1 field of the hippocampus and dentate gyrus in the same group. No correlations could be found between the seizure score or behavioral indices in the active avoidance test, or between the indices of the active avoidance learning and the number of undamaged cells in the hippocampus. However, in the control animals, negative correlations were demonstrated between the number of damaged cells in the CA1 and CA3 field and the number of avoidance reactions in the first and last learning sessions.