Effect of lumbar nerve root compression on primary sensory neurons and their central branches: changes in the nociceptive neuropeptides substance P and somatostatin.
METHODS
This study examined the effect of lumbar nerve root compression on nociceptive neuropeptides in the axonal flow using an in vivo model.


OBJECTIVE
The aim was to investigate changes in axonal flow after nerve root compression by using immunohistochemical techniques to detect substance P (SP) and somatostatin (SOM), which is thought to be involved in temperature and pain sensation.


BACKGROUND
Disturbance of intraradicular blood flow and nerve fiber deformation caused by mechanical compression are thought to be involved in the pathophysiology of diseases characterized by radicular symptoms, such as lumbar disc herniation and lumbar canal stenosis. However, little research has been conducted into the changes of axonal flow associated with nerve root compression.


METHODS
In dogs, the lumbar nerve roots were compressed using four types of clips with different pressures. Changes of SP and SOM levels in the spinal dorsal horn, dorsal root, and dorsal root ganglions were examined immunohistochemically after compression for 24 hours or 1 week.


RESULTS
After compression for 24 hours, axonal flow in the dorsal root was impaired, accumulation of SP and SOM was observed distal to the site of compression, and there was a decrease in the number of dorsal root ganglion cells showing positively for these neurotransmitters. Compression for 1 week resulted in a decrease in the number of SP- and SOM-positive fibers in the spinal dorsal horn.


CONCLUSIONS
Change of axonal flow resulting from direct nerve compression could affect the metabolism of neurotransmitters that flow inside the axons and may be a primary cause of the decline in nerve function.
Kobayashi
Shigeru
S
Department of Orthopaedics and Rehabilitation Medicine, Fukui University School of Medicine, Fukui, Japan. kshigeru@fmsrsa.fukui-med.ac.jp
Kokubo
Yasuo
Y
Uchida
Kenzo
K
Yayama
Takafumi
T
Takeno
Kenichi
K
Negoro
Kouhei
K
Nakajima
Hideaki
H
Baba
Hisatoshi
H
Yoshizawa
Hidezo
H
D000818:Animals; D001370:Axonal Transport; D015415:Biomarkers / Q000378:metabolism; D002452:Cell Count; D004195:Disease Models, Animal; D004285:Dogs; D005727:Ganglia, Spinal / Q000293:injuries / Q000473:pathology / Q000503:physiopathology; D007091:Image Processing, Computer-Assisted; D007124:Immunoenzyme Techniques; D008159:Lumbar Vertebrae; D009408:Nerve Compression Syndromes / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020671:Posterior Horn Cells / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D011843:Radiculopathy / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D013004:Somatostatin / Q000378:metabolism*; D013373:Substance P / Q000378:metabolism*
D015415:Biomarkers; D013373:Substance P; D013004:Somatostatin