The role of second messengers in the regulation of protein phosphorylation was studied in microvessels isolated from rat cerebral cortex. Calcium-calmodulin (CAM)-, Ca2+/phospholipid (PK C)-, cyclic GMP (cGMP)-, and cyclic AMP (cAMP)-dependent protein kinases were detected. Autophosphorylation of both the alpha- and beta-subunits of CAM-dependent protein kinase and the proteolytic fragment of the PK C enzyme was also detected. In other experiments, the effect of the protein kinase C enzyme inhibitor H-7 was examined on the brain oedema formation evoked by bilateral occlusion of the common carotid arteries in Sprague-Dawley rats of CFY strain.