Protein kinase C in the rat cerebral cortex during spreading depression

Activity and distribution of protein kinase C (PKC) in the rat cerebral cortex was correlated with the development of spreading depression. When the 'waves' of the slow potential shift, induced by topical application of concentrated KCl solutions, were allowed to spread over the cerebral cortex for 10 min, both cytosolic and particulate fractions of the enzyme were increased to 169% and 143%, respectively, of the control values obtained from the contralateral, relatively intact hemicortex. When the enzyme activities were correlated with development of a single slow potential shift, it appeared that in the cortical area fully depolarized (under the maximum of negativity), the respective values were 175% and 157%. One min after recovery of the single wave of spreading depression both cytosolic and particulate fractions continued to rise up to 218% and 239%, respectively. During 5 min of recovery both the cytosolic and particulate fractions fell to 71% and 57%, respectively, of control levels. Even at 10 min the cytosolic enzyme was still decreased to 80%. At 20 min no difference between control and experimental values was found (soluble, 111%; particulate, 96%). The results are discussed in the context of data obtained in a few studies dealing with depolarization-induced changes of PKC in vitro.