REVERSALS OF BLOOD PRESSURE RESPONSES CAUSED BY CHANGES IN FREQUENCY OF BRAIN STEM STIMULATION

Publisher Website
Google Scholar
Abstract
Two types of blood pressure reversals were found on stimulation of either the hypothala-mus or medulla. Low frequency reversals which showed a conversion from a fall to a rise in blood pressure occurred when the rate rose above 5 per sec. High frequency reversals occurred at critical stimulus rates between 10 and 150 per sec. Within the forebrain, low frequency reversals were distributed within the boundaries of the hypothalamus proper while high frequency reversals were limited to structures closely surrounding the hypothalamus anteriorly, dorsally, laterally and ventrally. Within the medulla ob-longata at levels of the inferior olive, low frequency reversals were distributed within the reticular formation while high frequency reversals were limited to structures such as the medial lemniscus, the vestibular nuclei, the restiform body, and the inferior olivary nucleus. Electrical records taken during the reversals showed that the direction of the blood pressure response was related to a rise or fall in the activity of the inferior cardiac nerve. Single sweep electrical records with single or paired stimuli to the hypothalamus, medulla or sciatic nerve not only showed the excitatory spike elicited by the stimulus, but demonstrated the disruptive effect of a strong shock upon the background activity, either normal or induced, in the inferior cardiac nerve.

This publication has 2 references indexed in Scilit: