The effects of mechanical compression and hypoxia on nerve root and dorsal root ganglia. An analysis of ectopic firing using an in vitro model.
METHODS
This study analyzed in vitro experiments of ectopic firing evoked by mechanical compression or hypoxia of canine lumbar dorsal roots with dorsal root ganglia using an in vitro model.


OBJECTIVE
The results were correlated to understand the pathophysiology of radiculopathy, which manifests abnormal sensation and pain.


BACKGROUND
It has been speculated that blood flow in the nerve root and mechanical compression play major roles in the production of radiculopathy symptoms. However, no precise experimental studies have been conducted on the relationship between these factors and the development of ectopic firing.


METHODS
Canine lumbar dorsal roots with dorsal root ganglia were immersed in an oxygenated artificial cerebrospinal fluid, and activity of the nerve root was recorded using bipolar platinum electrodes. Using this model, the effects of quantitative mechanical compression and hypoxia on the ectopic firing were analyzed.


RESULTS
When compression was applied, mechanical thresholds for eliciting firing were much lower in dorsal root ganglia than in dorsal roots, and the firing lasted for a longer period in dorsal root ganglia. Under hypoxia, dorsal root ganglia showed firing, and their thresholds from mechanical stimuli decreased significantly. In dorsal roots, impulse propagation was not affected, whereas firing was seen under the hypoxic condition.


CONCLUSIONS
Dorsal root ganglia are highly sensitive to mechanical compression and hypoxia and closely related to abnormal sensations and pain in radiculopathy.
Department of Orthopedic Surgery, Asahikawa Medical College, Japan.
O
O
Sugawara
Y
Y
Atsuta
T
T
Iwahara
T
T
Muramoto
M
M
Watakabe
Y
Y
Takemitsu
D000200:Action Potentials / Q000502:physiology; D000818:Animals; D001696:Biomechanical Phenomena; D004285:Dogs; D004594:Electrophysiology; D005727:Ganglia, Spinal / Q000503:physiopathology*; D000860:Hypoxia / Q000503:physiopathology / Q000662:veterinary*; D066298:In Vitro Techniques; D008161:Lumbosacral Region; D009408:Nerve Compression Syndromes / Q000503:physiopathology / Q000662:veterinary*; D009431:Neural Conduction / Q000502:physiology; D011843:Radiculopathy / Q000209:etiology; D013126:Spinal Nerve Roots / Q000503:physiopathology*