Partial Purification of Nuclear Protein Kinase from Small Dense Nuclei of Mouse Brain and the Effect of Chronic Morphine Treatment

Abstract: To deduce whether or not the nuclear protein kinase activity may be responsible for the change in phosphorylation of chromatin proteins during morphine tolerance‐dependence, the nuclear protein kinases from small dense nuclei of mouse brain have been partially purified by ammonium sulfate fractionation and phosphocellulose column chromatography. Two peaks of cyclic AMP‐independent nuclear protein kinase activity are eluted from the phosphocellulose column by a linear NaCl gradient. During morphine tolerance‐dependence, the specific activity of peak I, but not of peak 11, is increased significantly relative to placebo controls. This increase in nuclear protein kinase activity may partially account for the elevated chromatin protein phosphorylation in small dense nuclei of mouse brain seen during morphine tolerance‐dependence.