Density of perivascular nerves on some cerebral and extracerebral blood vessels.

The perivascular adrenergic nerves were counted as they crossed a grid-line superimposed on rat cerebral or femoral arteries and arterioles, and on the portal vein and its tributaries. The nerves were visualized with the formaldehyde-vapor, fluorescence technique. No support was received for the hypothesis that cerebral vessels are better innervated than extracerebral vessels. In fact, the density of nerves was significantly greater on the femoral and portal vessels than on the cerebral.