Regional Cerebral Blood Flow During Stimulation of Seventh Cranial Nerve

The right seventh cranial nerve (n. VII) was exposed intracranially via a suboccipital approach in each of eight cats. Measurements of cerebral blood flow (CBF) were made from superficial cortex, sulcal cortex, basal cortex, the basal ganglia, and the centrum semiovale of each cerebral hemisphere of each cat by autoradiography using 14 Cantipyrine. In six cats, measurements of CBF were made during electric stimulation of n. VII; in two of these, the nerve was sectioned before stimulation. In the remaining two cats, measurements were made after exposure but without stimulation of n. VII; in these cats, there were no side-to-side differences of CBF. In each of the four cats with n. VII intact, CBF values were lower on the stimulated side. In each of the two cats with n. VII sectioned, CBF values were higher on the stimulated side. Thus, stimulation of n. VII causes regional increases of CBF only when centripetal effects of stimulation are prevented. Cerebral vasodilatation has been observed by others during stimulation of a sectioned or an intact n. VII. When an intact nerve is stimulated, vasodilatation apparently is unable to compensate for decreases of CBF mediated centripetally through brain stem structures and extracranial or basal cerebral vessels; moreover, such vasodilatation may be due in part to regulatory responses of vessels to decreases of perfusion pressure.