Effect of stimulation of hypothalamus and reticular activating system on production of cardiac arrhythmia.

• The role of: the central nervous system in maintaining and modifying cardiac rhythmicity lias been extensively studied" by many investigators. Emphasis has been laid on the diencephalic region as a pathway for important neurovcgetative fibers. Pitts et al." showed that from both sides of the hypothalamus, multiple pathways descend, over which impulses converge on a single preganglioiiic sympathetic neuron. Van Bogaert' postulated that the diencephalic region serves as a passage of important neurovegetative fibers which connect with the medulla. Previous studies on the medulla oblongata' have shown that centers that increase the blood pressure in these regions comprise an extensive zone within the lateral reticular formation, while the depressor center is located in the medial reticular formation. Likewise, stimulation of the reticular formation of the mesencephalon produces both depressor and pressor responses. The experiments of other workers"" showed the importance of the reticular formation and corticospinal tracts for the transmission of the sympathetic impulses from the hypothalamus. "Weinberg and Foster ' 4 postulated that the posteromedial hypothalamus exerts an effect chiefly upon the sinus node, whereas the lateral hypothalamus and subthalamus exert their influence principally upon the myocardium.