BLOOD PRESSURE CHANGES IN RESPONSE TO ELECTRICAL AND CHEMICAL (ACETYL-BETA-METHYLCHOLINE) STIMULATION OF THE CEREBRAL CORTEX IN DOGS

Abstract

During a study of blood pressure centers in the dog''s cerebral cortex, the need was felt for a more physiologic type of stimulation than the electrical stimulus heretofore used. To this purpose, several chemical compounds (adrenaline, ephedrine, strychnine, prostigmin, acetyl-beta-methylcholine) were applied to the brain surface. Of these only acetyl-beta-methylcholine, used in a concn. of 2.5%, evoked a marked vasomotor response. When compared with vasomotor changes due to electrical stimulation these responses showed more detail, and were more pronounced and of longer duration. Also, if present, the response would always be completely developed. Vasomotor areas, slightly different for each individual animal, were found in the posterior sigmoid gyrus and in the anterior ectosylvian gyrus, both producing an abrupt blood pressure drop of 30 - 50 mm. Hg, with a latency of 30 - 40 sec. and a duration of 2 - 3 min. The effect was further characterized by the appearance of slow vasomotor waves (3d order waves) and could be prolonged considerably by simultaneous application of prostigmin which had no effect when used alone. Acetyl-beta-methylcholine may be considered a useful cortical stimulant approaching the ideal physiologic stimulus more closely than electrical stimulation.