Loss of the Spinal GABAergic System Is Involved in Chronic Central Pain Following a Spinal Cord Injury; Behavioral and Electrophysiological Evidences .

Gwak,  Young Seob; Shim,  Beom; Yoon,  Duck Mi; Nam,  Taick Sang; Paik,  Kwang Se; Leem,  Joong Woo

doi:2002.42.5.667

Experimental Research Article

Korean Journal of Anesthesiology 2002;42(5):667-676.
DOI: https://doi.org/10.4097/kjae.2002.42.5.667

Loss of the Spinal GABAergic System Is Involved in Chronic Central Pain Following a Spinal Cord Injury; Behavioral and Electrophysiological Evidences .

Young Seob Gwak, Beom Shim, Duck Mi Yoon, Taick Sang Nam, Kwang Se Paik, Joong Woo Leem

¹Department of Physiology, Yonsei University College of Medicine, Seoul, Korea. jwleem@yumc.yonsei.ac.kr
²Department of Anesthesiology, Yonsei University College of Medicine, Seoul, Korea.

Abstract

BACKGROUND
Allodynia, hyperalgesia, and spontaneous pain are symptoms characterized by chronic central pain which was frequently observed following a spinal cord injury (SCI). However, the underlying mechanism has not been fully understood. This study was conducted to investigate whether the loss of the GABAergic system in the spinal dorsal horn was involved in the development of central pain following a spinal cord injury.
METHODS
SCI was induced by a hemisection of the spinal cord at T13 in adult male Sprague-Dawley rats. Mechanical allodynia was tested by measuring paw withdrawal frequency in response to repeated applications of a von Frey hair to the plantar surface of the hind-paw. Single neuronal activity of the dorsal horn neurons (L4 L6) was recorded extracellularly using a carbon filament-filled glass microelectrode (2 4 MOhm). The drugs were intrathecally or topically administrated on the spinal surface for behavioral and electrophysiological experiments, respectively.
RESULTS
After a left spinal hemisection at T13, behavioral signs of mechanical allodynia developed on both hind-paws and responsiveness of spinal dorsal horn neurons increased on both sides of the spinal dorsal horn. GABA receptor agonists including GABAA and GABAB receptor subtypes suppressed mechanical allodynia on both sides of hind-paws and decreased responsiveness of spinal dorsal horn neurons on both sides of spinal cord.
CONCLUSIONS
These results indicate that a loss of the GABAergic system within the spinal cord plays a key role on the development of central pain following a spinal cord injury.

Key Words: Baclofen; central pain; GABA; muscimol; spinal cord injury