Protein kinase C exists as a large family of multiple subspecies with subtle individual characteristics. This heterogeneity comes from different genes as well as from different splicings of a single RNA transcript. The members of this family have closely related structures with a high degree of homology. Biochemical studies have shown that their mode of activation and kinetic and catalytic properties differ slightly from one another. By using a combination of biochemical and immunocytochemical techniques, their differential regional and cellular expression have been shown in the nervous tissues. Each member of this enzyme family may have a specialized function in transducing various physiological and pathological signals into different cell types.