The role of the sympathetic system in producing cardiac disturbances determined by stimulation of the midbrain reticular formation in the cat.

The authors check the theory according to which cardiac rhythm disturbances developing after myocardial infarction or in the course of a long Q-T interval syndrome are due to stimulation of the autonomic nervous system which innervates the heart via the stellate ganglia, the tonus of the left sympathetic being predominant over the right sympathetic at cardiac level. Six semiacute experiments were carried out on curarized cats in which arrhythmia was produced by stereotaxic electric stimulation of the midbrain reticular formation (MRF). Stimulation of MRF after either left or right stellectomy induced the same type of rhythm disturbances as that produced before stellectomy (ventricular extrasystoles and idioventricular paroxysmal tachycardia); however, latency in the development of these rhythm disturbances significantly increased after left stellectomy. After bilateral removal of the stellate ganglia, stimulation of the MRF only induced isolated or clustered ventricular extrasystoles. The results suggest that both stellate ganglia have an almost equal determinant role in the appearance of cardiac system disturbances obtained by stimulation of the MRF, the left having a somewhat more rapid effect.