The pathway of parasympathetic nerve fibers to cerebral vessels from the otic ganglion in the rat

It has previously been shown that the otic ganglion contributes to the innervation of pial arteries in the rat with parasympathetic fibers, but the exact pathway from the ganglion to the vessels has been unknown. Further, the precise course of the lesser superficial petrosal nerve in the rat has not been described. In this research we show, by combining retrograde neuronal tracer technique and immunohistochemical demonstration of transmitters, that the fibers leave the ganglion in the lesser superficial petrosal nerve, running on the anterior and medial inner surface of the tympanic bulla to reach the greater superficial petrosal nerve, and deviate via the deep petrosal nerve to the wall of the internal carotid artery. Various other nerves were excluded as possible pathways.