GABAergic neurons containing the Ca 2+-binding protein parvalbumin in the rat hippocampus and dentate gyrus

Abstract

The distribution Ca 2+-binding protein, parvalbumin (PV), containing neurons and their colocalization with glutamic acid decar☐ylase (GAD) were studied in the rat hippocampus and dentate gyrus using immunohistochemistry. PV immunoreactive (PV-I) perikarya were concentrated in the granule cell layer and hilus in the dentate gyrus and in the stratum pyramidale and stratum oriens in the CA 3 and CA 1 regions of the hippocampus. They were rare in the molecular layer of the dentate gyrus, in the stratum radiatum and in the stratum lacunosum-moleculare of the hippocampus. PV-I axon terminals were restricted to the granule cell layer, the stratum pyramidale and the immediately adjoining zones of these layers. Almost all PV-I neurons were also GAD immunoreactive (GAD-I), whereas only about 20% of GAD-I neurons also contained PV. The percentages of GAD-I neurons which were also immunoreactive for PV were dependent on the layer in which they were found; i.e. 40–50% in the stratum pyramidale, 20–30% in the dentate granule cell layer and in the stratum of CA 3 and CA 1 regions, 15–20% in the hilus and in the stratum lucidum of CA 3 region and only 1–4% in the dentate molecular layer in the stratum radiatum and the stratum lacunosum-moleculare of the CA 3 and CA 1 regions. PV-I neurons are a particular subpopulation of GABAergic neurons in the hippocampal formation. Based on their morphology and laminar distribution, they probably include basket cells and axo-axonic cells.