The role of nitric oxide in spinal nociceptive reflexes in rats with neurogenic and non-neurogenic peripheral inflammation.
This in vivo electrophysiological study concerns the role of nitric oxide (NO) in mechanical and thermal spinal nociceptive reflexes in alpha-chloralose anaesthetized rats. The effects of the NO synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME; 5-40 mg/kg i.v.) on reflexes were compared both in normal rats and in those with peripheral inflammation induced neurogenically (mustard oil) and non-neurogenically (carrageenan). Methoxamine (0.1 mg/kg i.v.) was used to mimic the marked hypertension caused by L-NAME. Thermal nociceptive reflexes were equally reduced by methoxamine and L-NAME in both normal and inflamed rats, implying that NO has no role in mediating thermal reflexes. However, L- (but not D-) NAME dose dependently and significantly inhibited mechanical reflexes in both carrageenan inflamed (to 37 +/- 12% control) and mustard oil inflamed rats (to 75 +/- 8% control). Moreover, these reductions were greater than those by methoxamine. In contrast, L-NAME did not reduce mechanical reflexes in rats with no inflammation or in spinalized rats with inflammation. The inhibition of mechanical reflexes with L-NAME in carrageenan inflamed rats was reversed and prevented by pre- or post-treatment with L- (but not D-) arginine (50-200 mg/kg i.v.). These data imply a supraspinal role for NO in mediating mechanical (but not thermal) nociceptive reflexes only in those rats with peripheral inflammation.
Semos
M L
ML
Department of Physiology, School of Medical Sciences, University Walk, Bristol, U.K.
Headley
P M
PM
D000594:Amino Acid Oxidoreductases / Q000037:antagonists & inhibitors; D000818:Animals; D001120:Arginine / Q000031:analogs & derivatives / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D008297:Male; D019331:NG-Nitroarginine Methyl Ester; D009443:Neuritis / Q000139:chemically induced / Q000503:physiopathology*; D009569:Nitric Oxide / Q000037:antagonists & inhibitors / Q000502:physiology*; D019001:Nitric Oxide Synthase; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology*; D010147:Pain Measurement / Q000187:drug effects; D010523:Peripheral Nervous System Diseases / Q000139:chemically induced / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors / Q000187:drug effects; D012018:Reflex / Q000502:physiology*; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*
D016194:Receptors, N-Methyl-D-Aspartate; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D019331:NG-Nitroarginine Methyl Ester