Protein kinase C subspecies distinguish major cell types in rat hippocampus: An immunocytochemical and in situ hybridization histochemical study

This study compares the distribution of protein kinase C (PKC) α and β with the distribution of PKC ∈ in the hippocampal formation of rats by immunocytochemistry and in situ hybridization histochemistry. Alpha and PKC β are members of the group A PKC genes that were first described; PKC ∈ is a member of the group B PKC genes that were more recently identified by molecular cloning. A combination of all three gene products and their mRNAs overlapped in their distributions in dentate granule cells and pyramidal and nonpyramidal neurons. However, each subspecies predominated in one of the major cell types. PKC α‐immunoreactivity and mRNA were most intense in CA2‐3 pyramidal cells and dendrites, whereas PKC β‐immunoreactivity and mRNA were most intense in CA1 pyramidal cells and dendrites. PKC ∈‐immunoreactivity and mRNA were concentrated in dentate granule cells and CA3 pyramidal cells. Furthermore, PKC ∈‐immunoreactivity was detectable in mossy fibers. Each subspecies labeled different kinds of interneurons that were particularly numerous in, but not restricted to, the hilus. These data support the contention that different subtypes of hippocampal neurons are distinguished by the expression of different combinations of PKC subspecies under resting conditions.