The cholinergic pathway to cerebral blood vessels

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Abstract
The application of cobalt chloride to the peripheral cut end of the greater superficial petrosal nerve (g.s.p.n.) in rats revealed that only a few fibres in the plexus of nerves on the adventitial surface of the internal carotid artery were in axonal continuity with the g.s.p.n. A similarly small contribution of cholinergic fibres to cerebral blood vessels from this nerve was suggested by the observation that section of the g.s.p.n. resulted in an insignificant reduction in the density of the AChE-staining plexus in the internal carotid and cerebral arteries and in the incidence of at most 2% degenerate terminals of those observed on the middle cerebral artery. Alternative explanations of the results are discussed: that the AChE-staining fibres are postganglionic, that the time course for degeneration is unasually slow and that non-cholinergic fibres stain non-specifically for AChE. It is concluded that a cholinergic dilator pathway is most probably carried by the g.s.p.n. but that it is not unique.