An Increase in Cerebral Blood Flow Elicited by Electrical Stimulation of the Solitary Nucleus in Rats with Cervical Cordotomy and Vagotomy

Abstract

The effect of monopolar electrical stimulation of the intermediate portion of the solitary nucleus (SOL) on brain circulation was investigated in 48 anesthetized (N2O), artificially ventilated Wistar rats. The cervical spinal cord and bilateral vago-sympathetic trunks were severed to eliminate any change in arterial blood pressure mediated by the autonomic nervous systems on stimulating the SOL. Blood pressure was kept within the physiological range by intravenous phenylephrine infusion. Current intensity of the stimulus was set at 60±4 µA (mean ±S.E.; n=9), which was equivalent to 2.5 times threshold for vasopressin-induced pressor response. A sufficient dose of vasopressin-antagonist given to each rat shortly before determination of cerebral blood flow, prevented vasopressin-induced hypertension from stimulating the medulla. Stimulation elicited an increase in regional blood flow (14C-iodoantipyrine technique) by 72%, and 39% on average in the frontal and occipital cortices, respectively, and 25% in the caudate-putamen (p<0.05; n=12 in control, and 9 in the stimulation studies). It was found that observed results included little detectable contribution from current spread of the stimulus toward the adjacent structures (dorsal medullary reticular formation and cuneate fasciculus) surrounding the SOL and from retrograde activation of the cerebellar fastigial nucleus. Overall, the present study suggests that a certain vasomotor mechanism, which is activated upon excitation of the intermediate portion of the SOL, regulates the blood vessels of the brain as a vasodilator. © 1985, PHYSIOLOGICAL SOCIETY OF JAPAN. All rights reserved.