NOS neurones lie near branchings of cortical arteriolae.

We show that numerous neurones labelled for NADPH-diaphorase, which synthetize nitric oxide, lie near branching points of the arteriolae which descend through the cerebral cortex from its pial surface. This spatial relationship suggests the possibility of neural control of cortical blood flow by the NADPH-diaphorase neurones, possibly mediated by the rapid action of nitric oxide.