C2 spinal cord stimulation induces dynorphin release from rat T4 spinal cord: potential modulation of myocardial ischemia-sensitive neurons

• Published in: American journal of physiology. Regulatory, integrative and comparative physiology Vol. 295; no. 5; pp. R1519 - R1528
• Main Authors: Ding, XiaoHui, Hua, Fang, Sutherly, Kristopher, Ardell, Jeffrey L, Williams, Carole A
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.11.2008
• Subjects: Analgesics; Animals; Brain Stem - cytology; Brain Stem - drug effects; Brain Stem - metabolism; Cardiovascular disease; Coronary Vessels - physiology; Dynorphins - metabolism; Electric Stimulation; Excitatory Amino Acid Agonists - pharmacology; Hormones; Ibotenic Acid - pharmacology; Image Processing, Computer-Assisted; Immunohistochemistry; Male; Myocardial Ischemia - metabolism; Myocardial Ischemia - physiopathology; Naltrexone - administration & dosage; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Narcotic Antagonists - administration & dosage; Narcotic Antagonists - pharmacology; Neural Pathways - drug effects; Neural Pathways - physiology; Neurohumoral Control of Cardiovascular Function; Neurons; Neurons - drug effects; Neurons - metabolism; Neurons - physiology; Peptides; Posterior Horn Cells - drug effects; Posterior Horn Cells - metabolism; Proto-Oncogene Proteins c-fos - metabolism; Rats; Rats, Sprague-Dawley; Rodents; Spinal cord; Spinal Cord - metabolism; Spinal Cord - physiology; Spinal Cord - physiopathology; Substance P - metabolism
• ISSN: 0363-6119; 1522-1490
• DOI: 10.1152/ajpregu.00899.2007

Departments of 1 Physiology, 2 Pharmacology, 3 Surgery, Quillen College of Medicine, East Tennessee State University, Johnson City, Tennessee Submitted 17 December 2007 ; accepted in final form 22 August 2008 During myocardial ischemia, the cranial cervical spinal cord (C1–C2) modulates the central processing of the cardiac nociceptive signal. This study was done to determine 1 ) whether C2 SCS-induced release of an analgesic neuropeptide in the dorsal horn of the thoracic (T4) spinal cord; 2 ) if one of the sources of this analgesic peptide was cervical propriospinal neurons, and 3 ) if chemical inactivation of C2 neurons altered local T4 substance P (SP) release during concurrent C2 SCS and cardiac ischemia. Ischemia was induced by intermittent occlusion of the left anterior descending coronary artery (CoAO) in urethane-anesthetized Sprague-Dawley rats. Release of dynorphin A (1-13), (DYN) and SP was determined using antibody-coated microprobes inserted into T4. SCS alone induced DYN release from laminae I–V in T4, and this release was maintained during CoAO. C2 injection of the excitotoxin, ibotenic acid, prior to SCS, inhibited T4 DYN release during SCS and ischemia; it also reversed the inhibition of SP release from T4 dorsal laminae during C2 SCS and CoAO. Injection of the -opioid antagonist, nor-binaltorphimine, into T4 also allowed an increased SP release during SCS and CoAO. CoAO increased the number of Fos-positive neurons in T4 dorsal horns but not in the intermediolateral columns (IML), while SCS (either alone or during CoAO) minimized this dorsal horn response to CoAO alone, while inducing T4 IML neuronal recruitment. These results suggest that activation of cervical propriospinal pathways induces DYN release in the thoracic spinal cord, thereby modulating nociceptive signals from the ischemic heart. antibody-coated microprobes; substance P; analgesic peptides; neuromodulation Address for reprint requests and other correspondence: C. A. Williams, Dept. of Physiology, East Tennessee State Univ., Stanton-Gerber Hall B137, P.O. Box 70576, Johnson City, TN 37614-1708 (e-mail: williams{at}etsu.edu )