Cerebral vasodilatation produced by brain-stem stimulation: neurogenic control vs. autoregulation

Abstract

Cere-bral autbregulation and the response of cerebral vessels to brain-stem stimulation were assessed in monkeys. Cerebral blood flow was measured with electromagnetic flowmeters on the common carotid arteries. The external carotid circulation was eliminated. A primary effect of brain-stem stimulation on cerebral blood flow could not be distinguished from autoregulation in the presence of arterial pressor responses. Blood flow often increased above control during arterial depressor responses indicating primary cerebral vasodilatation. Stimulation of the brain stem produced an increase in cerebral blood flow without a change in blood pressure in 5 of 7 cord-sectioned animals. The average maximum increase in blood flow was 40%, and the latency was 1-4 sec. Evidence is presented that cerebral vasodilatation produced by stimulation of the brain stem is most likely neurogenic in origin.