Area-Specific Postnatal Maturation of the Calcium-Binding Proteins Parvalbumin- and Calbindin-Immunoreactive Neurons in the Rat Hippocampus

ABSTRACT

The present study was attempted to obtain the regional differences of development of the parvalbumin- and calbindin-ir neurons in the maturing rat hippocampus. Sprague-Dawley rats at 3, 7 days, 2, 3, 4, 5, 6, and 9 weeks of age were transcardially perfused with 4% paraformaldehyde fixative. The hippocampus was cut into 30 or 40(m sections with a cryostat. Immunohistochemical staining was performed for the parvalbumin and the calbindin using ABC method. The parvalbumin-ir neurons and their axon plexuses achieved the adult patterns as following sequences;CA2 and CA3 at ghe second postnatal week, CA1 at the third week, and dentate granule cell layer by fifth postnatal week. In addition, the calbindin-ir neurons showed the adult patterns by second postnatal week in CA2, CA3, mossy fibers, and the molecular layer of the dentate gyrus, the CA1 at the third week, and finally the dentate granular cell layer by fifth week. These results revealed that time course of the maturation of the parvalbumin- and calbindin-ir neurons in the rat hippocampus showed an area-specificity. The delayed maturation of CA1 and the latest maturation of the dentage granular cell layer suggested that the neurons in these locations seemed to exhibit differential responses to the conditions of increased intracellular calcium, when compared with other areas or with the adult hippocampus.