A change of nitric oxide in rat DRG following Freund's Complete Adjuvant induced inflammtory pain / 대한해부학회지

ABSTRACT

It has been reported that injection of Freund's complete adjuvant (FCA) into the hindpaw of a rat induces inflammatory responses with accompanying pain behaviors. Signs of pain behaviors observed in FCA-injected animals were reported to be similar to symptoms seen in patients with inflammatory pain. The nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d) is a selective histochemical marker for the nitric oxide synthesizing enzyme, nitric oxide synthase (NOS). N (G)-nitro-L-arginine methyl ester (L-NAME) is a NOS inhibitor. In the present study, we examined if inflammaory pain causes increases in NADPH-diaphorase reactivities in neurons of the dorsal root ganglia (DRG). The results were as follows; 1. FCA-induced inflammation on a limb increased staining density (SD) of NADPH-d positive neurons in the ipsilateral side DRG. 2. Pretreatment of L-NAME did not changed SD of NADPH-d positive neurons on the inflammation of contralateral side DRG 3. Posttreatment of L-NAME decreased the inflammation induced SD of NADPH-d positive neurons. 4. n-NOS immunoreactivity did not match NADPH-d histochemical study, implying the constant level of enzyme itself. Inflammation pain on a hindlimb increased staining density of NADPH-diaphorase positive neuron in the DRG, which was decreased by L-NAME. L-NAME also decreased pain perception. This suggests a role of NO in the pain perception and/or modulation at the level of DRG.