Patterns of hippocampal neuronal loss and axon reorganization of the dentate gyrus in the mouse pilocarpine model of temporal lobe epilepsy

Two distinct patterns of neuronal loss were observed in the CA3 area of the hippocampus in a mouse model of temporal lobe epilepsy.

• Type 1 neuronal loss involved partial loss of pyramidal neurons, while type 2 resulted in almost complete loss.
• Changes in associational and commissural connections in the dentate gyrus varied between mice with type 1 and type 2 loss.
• Mice with type 1 loss retained calretinin-immunopositive mossy cells and their fibers, whereas these were nearly absent in type 2 loss.
• Retrograde labeling indicated that cholera toxin subunit B colocalized with calretinin in the ventral hilus of type 1 loss mice, but not in type 2.
• PHA-L-immunopositive boutons sprouted from the dentate gyrus to contact surviving neurons in the CA1 area.
• Different patterns of neuronal loss in the CA3 area may be linked to distinct axonal reorganizations in the dentate gyrus.

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