title: Possible mechanism of painful radiculopathy in lumbar disc herniation.
abstract: The pathophysiologic mechanisms of painful radiculopathy caused by a herniated intervertebral disc remain unknown. This study sought to determine whether the autologous intervertebral disc produces pain related behavior and whether phospholipase A2 and nitric oxide are involved in the pathophysiologic mechanism producing the behavior. A rat model, in which autologous intervertebral discs were implanted on the nerve root in the lumbar spine, was used to measure hyperalgesia, which is a pain related behavior in the rat. In this experimental model, autologous nucleus pulposus and anulus fibrosus transplanted to lumbar nerve roots produced mechanical and thermal hyperalgesia, respectively. Epidural injection of a selective inhibitor for phospholipase A2 resulted in the disappearance of hypersensitivity to noxious mechanical stimuli. Thermal hyperalgesia produced by application of the anulus fibrosus was abated and abolished by epidural injections of saline and one of the inhibitors for nitric oxide synthase, respectively. The authors suggest that chemical mediators such as phospholipase A2 and nitric oxide, induced by extruded or sequestrated intervertebral discs, are involved in the pathophysiologic mechanisms of painful radiculopathy in lumbar disc herniations. This study may be useful in attempting to develop new medical approaches for treatments of lumbar disc herniation.
authors.affiliation: Department of Orthopedic Surgery, Wakayama Medical College, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kawakami
authors.forename: T
authors.initials: T
authors.lastname: Tamaki
authors.forename: N
authors.initials: N
authors.lastname: Hayashi
authors.forename: H
authors.initials: H
authors.lastname: Hashizume
authors.forename: H
authors.initials: H
authors.lastname: Nishi
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D004195:Disease Models, Animal; D006930:Hyperalgesia / Q000201:enzymology / Q000209:etiology* / Q000503:physiopathology; D007405:Intervertebral Disc Displacement / Q000150:complications* / Q000201:enzymology / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000293:injuries* / Q000294:innervation; D008297:Male; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D017288:Pain Threshold / Q000502:physiology; D010523:Peripheral Nervous System Diseases / Q000201:enzymology / Q000209:etiology* / Q000503:physiopathology; D010741:Phospholipases A / Q000037:antagonists & inhibitors / Q000378:metabolism; D054467:Phospholipases A2; D051381:Rats; D017207:Rats, Sprague-Dawley; D011930:Reaction Time / Q000502:physiology; D013126:Spinal Nerve Roots
chemical_list: D019001:Nitric Oxide Synthase; D010741:Phospholipases A; D054467:Phospholipases A2