Changes in parvalbumin-immunoreactive neurons in the rat hippocampus following a kainic acid lesion

Changes in a sub-population of hippocampal non-pyramidal neurons following a unilateral lesion with kainic acid were examined using an antibody raised against the Ca-binding protein parvalbumin. A loss of 71-97% of the parvalbumin-immunoreactive neurons occurred at the three post-lesion times studied (1, 2 and 4 weeks) in all areas of the ipsilateral hippocampus, but no such loss was observed in the dentate gyrus. Resistant parvalbumin-immunoreactive neurons occurred principally in stratum pyramidale and displayed altered morphology from the normal with swollen dendrites and dendritic varicosities. The contralateral hippocampus exhibited losses of parvalbumin-immunoreactive cells, but this was restricted to stratum oriens of CA1. This data demonstrates the loss of a specific and important population of non-pyramidal neurons which might be responsible for the chronic loss of functional inhibition seen in this animal model of temporal lobe epilepsy.