Differential expression of PKC isoforms in hippocampal neuronal cultures: modifications after basic FGF treatment.

Protein kinase C (PKC) is present in high concentrations in neuronal tissues and participates in various neuronal functions. Ten isoforms have so far been identified and each PKC isoform may be activated by a variety of stimuli. By immunoblot analysis the presence of PKC isoforms was examined in dissociated cell cultures of the hippocampus and during the development in vivo. As soon as embryonic day 17 the hippocampus contains detectable amounts of PKC epsilon and zeta and low levels of PKC alpha. PKC beta and gamma appear during the first and second post-natal week. All isoforms progressively increase until the adult age. Cultures of hippocampal neurons derived from rat embryos express PKC alpha, epsilon and zeta whereas PKC beta and gamma are undetectable; a distinct pattern is observed in cultures of hippocampal glial cells. The neuronal levels of PKC alpha, epsilon and zeta increase during the period in culture and are enhanced when hippocampal neurons are exposed to the continuous presence of basic fibroblast growth factor. Immunofluorescence of PKC epsilon and zeta occupies all the cytoplasmic neuronal compartment. The early expression of some PKC isoforms in cultures of post-mitotic hippocampal neurons suggest their involvement in morphological events that occur during this period; in particular the neuritic outgrowth.