Adrenergic innervation of large cerebral blood vessels of the rabbit studied by fluorescence microscopy. Absence of features that might contribute to non-uniform change in cerebral blood flow.

The literature provides evidence for non-uniform regional changes in cerebral blood flow under a variety of circumstances. Possible causes of such changes were sought in the larger cerebral arteries of the rabbit prepared according to the glyoxylic acid fluorescence histochemical technique. The adrenergic innervation of the circle of Willis, the basilar artery and their main branches, although showing small differences, is essentially of uniform density. There is no evidence for collars of adrenergic nerves around the origin of small branches nor for cushions at their orifices. Innervation density appears to diminish as the pial vessels get smaller and all vessels seem to be innervated. Thus non-uniform alterations of cerebral blood flow cannot be accounted for by these factors.