Atrial Arrhythmias and Autonomic Dysfunction in Rats Exposed to Chronic Intermittent Hypoxia.

This study investigated the effects of CIH on atrial electrophysiology and arrhythmia vulnerability, and evaluated the role of autonomics in CIH promotion of AF. Adult male Sprague-Dawley rats were exposed to 8h/day of CIH or normoxia for 7 days. Following exposure, rats were anesthetized for intracardiac electrophysiological studies. Atrial effective refractory periods (AERPs) and AF inducibility were determined using programmed electrical stimulation (PES) and burst pacing in the absence and presence of autonomic receptor agonists and antagonists. Western blot analysis measured atrial protein expression of muscarinic M2, M3 and β1-adrenergic receptors. Compared to normoxic controls, CIH rats had enhanced AF vulnerability using both PES and burst pacing, accompanied by greater AERP responses to carbachol and propranolol, lesser responses to isoproterenol and higher atrial M2 receptor protein levels. Enhanced atrial vulnerability was accentuated by carbachol and abolished by atropine, indicating that AF-promoting effects of CIH depended principally on parasympathetic activation. Enhancement of atrial vulnerability and AERP shortening with cholinergic agonists in CIH rats is consistent with sensitivity to parasympathetic activation. Higher responses to adrenergic receptor blockade in CIH rats is consistent with sympathetic potentiation. These findings implicate CIH as an important mediator of enhanced AF susceptibility in OSA and provide novel insights into the underlying mec...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research