[Effects of stimulation of the vertebral nerve around the proximal vertebral artery on pupil and the autonomic nervous system--a contribution to pathophysiology of Powers' intermittent vertebral artery compression syndrome].

In order to elucidate the pathophysiology involved in Powers' intermittent vertebral artery compression syndrome, the author investigated sympathetic and parasympathetic changes produced by stimulation of nerves around the proximal vertebral artery (the vertebral nerve) in anesthetized and immobilized cats. These changes were observed mainly through pupillary changes, pulse and blood pressure, evoked potentials in the lateral horn of the upper thoracic cord (centrum ciliospinale), in the cervical sympathetic trunk, and in the short ciliary nerve. Electrical stimulation of vertebral nerve and local application of K ion around the vertebral artery produced stimulus-dependent ipsilateral mydriasis; when stimulation of higher strength was applied pronounced ipsilateral and mild contralateral mydriasis and hypertension occurred. Electrical stimulation of perivascular tissue around the subclavian artery proximal to origin of the vertebral artery showed ipsilateral mydriasis; while on stimulating the distal subclavian, the costcervical, the omocervical and the internal thoracic arteries did not show any pupillary response. Neuronal discharges in the lateral horn of upper thoracic cord and in the cervical sympathetic trunk showed stimulus-dependent increases on stimulating the vertebral nerve; while, inhibitory responses were observed in the short ciliary nerve formed by parasympathetic nerve fibers. From the data available, it seems likely that the stimulation of periarterial neural structure of the vertebral artery produced sympathetic excitatory as well as parasympathetic inhibitory neuronal discharges simultaneously may probably be derived from the integrating autonomic center in the hypothalamus.