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The change in the heart rate and arrhythmias produced by electrical stimulation of the brain stem of dogs were observed and analyzed.The results are as follows ; (1) In the early phase of the stimulation, sinus tachycardia was mostly observed, especially marked on the stimulation of the posterior part in the hypothalamus, the midline, ventral and medial nuclei groups in the thalamus and the posterior commissure, the central gray stratum and a part of reticular formation in the midbrain. Sinus bradycardia was infrequent and not so marked.(2) In the late phase or after the end of the stimulation, bradycardia was often observed and sometimes accompanied by such arrhythmias as atrioventricular block, nodal escaped beat or nodal escaped rhythm. This phenomenon was marked especially when blood pressure was elevated remarkably. It was explained mainly as vagal reflex, partly delayed vagal reaction of the stimulated area.(3) Ventricular extrasystole induced by central nervous stimulation was classified into 2 groups 'A' and 'B', according to the mode of appearance. The extrasystole of type 'A' appeared in the early phase of the stimulation, independently upon elevation of the blood pressure and was perhaps of right ventricular origin. The extrasystole of type 'B', the appearance of which was similar to that of escaped beat (that is, of longer coupling), occurred in the late phase or after the cessation of the stimulation, associated with a blood pressure elevation and was thought to be of left ventricular origin. While the extrasystole of type 'A' seems to be of direct central nervous origin, the one of type 'B' is considered of secondary nature.(4) The distribution of the area participating with the extrasystole of type 'A' was relatively restricted to the median portion of the brain stem. These area may have some function to influence the heart to produce ventricular extrasystoles.
UEDA et al. (1962) studied this question.