Abstract
The distribution of cyclic GMP-dependent protein kinase in rat brain has been studied by an immunological approach involving radioimmunoassay and fluorescence immunohistochemistry. Data obtained by radioimmunoassay indicate that cyclic GMP-dependent protein kinase is 20- to 40-fold more concentrated in cerebellum than in other brain regions. Immunohistochemical experiments demonstrate that the high concentration of immunoreactivity of the protein kinase in cerebellum is attributable to Purkinje cells. Immunoreactivity in these cells is homogeneously distributed throughout the cell (perikarya, dendrites, and axons) with the exception of the nucleus. No other neurons either in the cerebellum or in other brain regions were stained by antiserum to the protein kinase. Immunoreactivity, however, was found throughout the brain on smooth muscle cells of blood vessels.