Submitted on October 9, 2008
Revised on May 27, 2009
Accepted on June 5, 2009
Dorsal spinal cord stimulation obtunds the capacity of intrathoracic extracardiac neurons to transduce myocardial ischemia
Jeffrey Laurence Ardell1*, Rene Cardinal2, Michel Vermeulen3, and John Andrew Armour4
1 East Tennessee State University
2 Hopital du Sacre-Coeur de Montreal
3 Hopital du Sacre-Coeur
4 University of Montreal
* To whom correspondence should be addressed. E-mail: ardellj{at}etsu.edu.
Populations of intrathoracic extracardiac neurons transduce myocardial ischemia, thereby contributing to sympathetic control of regional cardiac indices during such pathology. Our objective was to determine whether electrical neuromodulation using spinal cord stimulation (SCS) modulates such local reflex control. Methods. In 10 anesthetized canines, middle cervical ganglion neurons were identified that transduce the ventricular milieu. Their capacity to transduce a global (rapid ventricular pacing) versus regional (transient regional ischemia) ventricular stress was tested before and after SCS (50 Hz, 0.2 msec duration at 90% motor threshold) applied to the dorsal aspect of the T1 to T4 spinal cord. Rapid ventricular pacing and transient myocardial ischemia both activated cardiac related middle cervical ganglion neurons. SCS obtunded their capacity to reflexly respond to the regional ventricular ischemia, but not rapid ventricular pacing. Conclusions. Spinal cord inputs to the intrathoracic extracardiac nervous system obtund the latter's capacity to transduce regional ventricular ischemia, but not global cardiac stress. Given the substantial body of literature indicating the adverse consequences of excessive adrenergic neuronal excitation on cardiac function, these data delineate the intrathoracic extracardiac nervous system as a potential target for neuromodulation therapy in minimizing such effects.
