CHANGES IN PARVALBUMIN-IMMUNOREACTIVE NEURONS IN THE RAT HIPPOCAMPUS FOLLOWING A KAINIC ACID LESION

Changes in a sub-population of hippocampal non-pyramidal neurons follo wing a unilateral lesion with kainic acid were examined using an antib ody 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 ipsilater al hippocampus, but no such loss was observed in the dentate gyrus. Re sistant parvalbumin-immunoreactive neurons occurred principally in str atum pyramidale and displayed altered morphology from the normal with swollen dendrites and dendritic varicosities. The contralateral hippoc ampus exhibited losses of parvalbumin-immunoreactive cells, but this w as restricted to stratum oriens of CA1. This data demonstrates the los s of a specific and important population of non-pyramidal neurons whic h might be responsible for the chronic loss of functional inhibition [ 3] seen in this animal model of temporal lobe epilepsy.