Download 2016 department of medicine research day

2016 DEPARTMENT OF MEDICINE RESEARCH DAY
Title of Poster: Spinal dorsal column and vagus nerve stimulation modulate vagal
afferent transduction of myocardial ischemia
Presenter: Siamak Salavatian
Division: Cardiology
☐ Faculty ☒ Fellow ☐ Resident ☐ Post-doc Research Fellow ☐ Graduate Student ☐ Medical Student ☐Other
Principal Investigator/Mentor: Dr.Jeffrey Laurence Ardell
Co-Investigators:
Thematic Poster Category: Neurobiology, Smooth, Striated and Cardiac Muscle Function, Cardiac Conduction
Systems and Arrhythmias, Biology of Perception and Pain, Psychoneuroimmunology
Abstract
Background: Autonomic regulation therapy (ART), including vagus nerve stimulation (VNS) and
spinal cord stimulation (SCS), is an emerging therapy in managing heart diseases, doing so by
modulating multiple elements of the cardiac neuronal hierarchy.
Objective: To determine if ART impacts primary cardiac sensory afferent transduction of myocardial
ischemia (MI).
Methods: Using extracellular recordings in anesthetized canines, cardiac-related nodose ganglia
neurons were identified by their response to epicardial touch, great vessel occlusion (inferior vena
cava occlusion and descending aorta) and chemical activation of sensory neurites with epicardial
veratridine. Neural responses to 1 min left anterior descending (LAD) coronary artery occlusion (CAO)
were then evaluated prior to and following either SCS [T1-T3 spinal level; 50Hz, 90% motor
threshold] or cervical VNS [20 Hz; 1.2x threshold]. Cardiac nodose neural activity was also assessed
at progressive levels of VNS [2 Hz; 1-8 mA].
Results: 65% of cardiac-related nodose neurons responded to LAD CAO, with activity increasing
~140% (0.33±0.08 to 0.79±0.19 impulses/sec, p=0.001). The neural response to LAD CAO was
suppressed by SCS (0.85±0.3 to 0.11±0.4, p=0.03) or VNS (0.74±0.26 to 0.11±0.05, p=0.03).
Nodose neural activity increased progressively with VNS current from 1 to 5 mA (0.2±0.1 to 0.69±0.1
impulses/sec, p=0.005) but decreased when VNS current exceeded 5 mA (0.69±0.1 to 0.12±0.08
impulses/sec, p=0.004).
Conclusions: LAD CAO activates multi-modal and nociceptive afferent inputs to the central nervous
system. VNS and SCS have the capability to obtund this afferent response, likely doing so by
modifying the myocyte/nerve interface. Cardiac nodose neurons did not show linear response to
progressive VNS, indicating they are not simple relay stations, and these processing capabilities of the
nodose include a damping function in response to excessive neural input.