Distribution of Nitric Oxide Synthase in the Human Cerebral Blood Vessels and Brain Tissues

The distribution of nitric oxide synthase was investigated in human cerebral blood vessels and brain tissues. NADPH-diaphorase histochemistry, which is a marker for nitric oxide synthase in neurons and endothelial cells, revealed periadventitial nerve fibers in the arteries of the circle of Willis and their cortical branches, as well as the common carotid and subclavian arteries. The fibers were mostly nonvaricose in the periadventitial nerve trunk and were varicose within the adventitia. Patchy reaction products were distributed in the perinuclear region of each endothelial cell. Smooth muscle cells in the tunica media were weakly stained. Staining was particularly intense in regions with atherosclerotic changes, which consist of macrophage infiltration and proliferation of fibroblasts. In the neural parenchyma, two types of NADPH-diaphorase reactive neurons were differentiated. Type I neurons were intensely stained, medium-sized, and bipolar or multipolar. They were distributed in the cerebral cortex an...