OBJECTIVETo observe the analgesic effect of sinomenine on the neuropathic pain rat model induced by SSNI, and discuss its impact on monoamine neurotransmitters in striatal extracellular fluid.

METHODMale SD rats were randomly divided into the sham operation group, the SSNI model group, the gabapentin group (100 mg x kg(-1)), the sinomenine high dose group (40 mg x kg(-1)) and the sinomenine low dose group (20 mg x kg(-1)). Mechanical hyperalgesia and cold pain sensitivity were evaluated by Von Frey hairs and cold spray. Striatum was sampled by microdialysis. High performance liquid chromatography-electrochemical detector (HPLC-ECD) were used to detect the content of such neurotransmitters as monoamine neurotransmitters noradrenaline (NE), dopamine (DA), 5-hydroxy tryptamine (5-HT) and their metabolites dihydroxyphenylacetic phenylacetic acid (DOPAC) and 5-hydroxyindoleacetic acid (5-HIAA).

RESULTSSNI model rats showed significant improvement in mechanical withdrawal threshold and cold pain sensitivity, significant decrease in intracerebral NE and notable increase in DA, 5-HT and their metabolites. Compared with the model group, the sinomenine high dose group showed significant increase in mechanical withdrawal threshold at 60, 90, 180 and 240 min after abdominal administration (P < 0.01), significant decrease in cold pain sensitivity score during 30-240 min (P < 0.05). Sinomenine can significantly up-regulated NE content in striatal extracellular fluid during 45-135 min (P < 0.05), remarkably reduce DA content and DOPAC at 45, 75 and 135 min (P < 0.05), 5-HT content during 45-135 min, DOPAC during 75-165 min (P < 0.05), and 5-HIAA during 45-135 min (P < 0.05).

CONCLUSIONSinomenine has the intervention effect on neuropathic pain in SSNI model rats. Its mechanism may be related to disorder of monoamine neurotransmitters in striatal extracellular fluid.