CA2+ CALMODULIN PROTEIN-KINASE AND PROTEIN-KINASE-C EXPRESSION DURINGDEVELOPMENT OF RAT HIPPOCAMPUS/

The expression of the genes encoding the alpha subunit of type-II calc ium/calmodulin-dependent protein kinase (CAM-KII alpha) and the gamma subspecies of protein kinase C (PKC gamma) was examined throughout pos tnatal rat brain development by in situ hybridization histochemistry. CAM-KII alpha was found to be expressed sequentially over the differen t hippocampal subregions, beginning with expression in the pyramidal c ells of CA3 at birth, followed by expression in the external blade of the dentate gyrus and in CA1 on postnatal day (PND) 5 and, finally, on PND 8 in the internal blade of the dentate gyrus. PKC gamma expressio n, in contrast, rose simultaneously in the hippocampal subregions CA1 and CA3, with little expression over the dentate gyrus. This fashion o f expression corresponds to the similar maturational state of the pyra midal cells in CA1 and CA3, whereas CAM-KII alpha expression during de velopment of the rat hippocampus follows the time table of afferent la mination, which is delayed in CA1 compared to CA3. Furthermore, we fou nd a temporal overexpression of CAM-KII alpha in the hippocampal subfi elds CA1 and CA3 at the end of the second postnatal week which coincid es with the development of N-methyl-D-aspartate receptor binding.