Distribution and pathway of the cerebrovascular nerve fibers from the otic ganglion in the rat: anterograde tracing study.

The distribution and pathway of cerebrovascular nerve fibers from the otic ganglion were studied by an anterograde tracing technique in the rat. Wheat germ agglutinin-horseradish peroxidase was injected as an anterograde axonal tracer into the otic ganglion on one side. Forty-eight hours later, the animals were killed and specimens were reacted with tetramethylbenzidine. Wheat germ agglutinin-horseradish peroxidase positive fine nerve fibers were observed in the circle of Willis and its branches, i.e., anterior cerebral artery, middle cerebral artery, internal ethmoidal artery and posterior cerebral artery, while no positive fiber could be detected in the vertebrobasilar artery. A positive reaction with tetramethylbenzidine was also observed in the lesser superficial petrosal nerve, the greater superficial petrosal nerve, the vidian nerve, the greater deep petrosal nerve, the internal carotid ganglion and the trigeminal ganglion. The sphenopalatine ganglion, however, failed to reveal any positive neurons or nerve fibers. It is concluded that the cerebrovascular nerve fibers originating from the otic ganglion run along the lesser superficial petrosal nerve to join the greater superficial petrosal nerve. They then reach the greater deep petrosal nerve and ascend along the internal carotid artery to distribute themselves to the cerebral blood vessels. This study demonstrated, for the first time, that the otic ganglion innervates the cerebral vessels and elucidated the pathway from the otic ganglion to the cerebral vessels directly by means of an anterograde axonal tracing technique.