Ca2+/calmodulin protein kinase and protein kinase C expression during development of rat hippocampus

The expression of the genes encoding the alpha subunit of type-II calcium/calmodulin-dependent protein kinase (CAM-KII alpha) and the gamma subspecies of protein kinase C (PKC gamma) was examined throughout postnatal rat brain development by in situ hybridization histochemistry. CAM-KII alpha was found to be expressed sequentially over the different hippocampal subregions, beginning with expression in the pyramidal cells 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 expression, in contrast, rose simultaneously in the hippocampal subregions CA1 and CA3, with little expression over the dentate gyrus. This fashion of expression corresponds to the similar maturational state of the pyramidal cells in CA1 and CA3, whereas CAM-KII alpha expression during development of the rat hippocampus follows the time table of afferent lamination, which is delayed in CA1 compared to CA3. Furthermore, we found a temporal overexpression of CAM-KII alpha in the hippocampal subfields CA1 and CA3 at the end of the second postnatal week which coincides with the development of N-methyl-D-aspartate receptor binding.