Stochastic behavior of atrial and ventricular intrinsic cardiac neurons

1 Department of Cardiology, Technical University RWTH, Aachen, Germany; Departments of 2 Physiology and Biophysics and 3 Physics, Dalhousie University, Halifax, Nova Scotia, Canada; 4 Department of Pharmacology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee; and 5 Department of Pharmacology, Faculty of Medicine, University of Montréal, Montréal, Québec, Canada Submitted 21 October 2005 ; accepted in final form 15 February 2006 To quantify the concurrent transduction capabilities of spatially distributed intrinsic cardiac neurons, the activities generated by atrial vs. ventricular intrinsic cardiac neurons were recorded simultaneously in 12 anesthetized dogs at baseline and during alterations in the cardiac milieu. Few (3%) identified atrial and ventricular neurons (2 of 72 characterized neurons) responded solely to regional mechanical deformation, doing so in a tightly coupled fashion (cross-correlation coefficient r = 0.63). The remaining (97%) atrial and ventricular neurons transduced multimodal stimuli to display stochastic behavior. Specifically, ventricular chemosensory inputs modified these populations such that they generated no short-term coherence among their activities (cross-correlation coefficient r = 0.21 ± 0.07). Regional ventricular ischemia activated most atrial and ventricular neurons in a noncoupled fashion. Nicotinic activation of atrial neurons enhanced ventricular neuronal activity. Acute decentralization of the intrinsic cardiac nervous system obtunded its neuron responsiveness to cardiac sensory stimuli. Most atrial and ventricular intrinsic cardiac neurons generate concurrent stochastic activity that is predicated primarily upon their cardiac chemotransduction. As a consequence, they display relative independent short-term (beat-to-beat) control over regional cardiac indexes. Over longer time scales, their functional interdependence is manifest as the result of interganglionic interconnections and descending inputs. atrial neuron; intrinsic cardiac nervous system; myocardial ischemia; stochastic control; ventricular neuron Address for reprint requests and other correspondence: J. A. Armour, Centre de recherché, Hôpital du Sacré-Coeur, 5400 boul. Gouin ouest, Montréal, Québec, H4J-1C5, Canada (e-mail: JA-Armour{at}crhsc.rtss.qc.ca )