OBJECTIVETo observe the analgesic effect of CQM on photochemically-induced prosopalgia model rats, and discuss its impact on the exciting amino acid neurotransmitter-glutamate (Glu).

METHODMale SD rats were randomly divided into the sham operation group and the prosopalgia group. And the latter was subdivided into the model group, the gabapentin group (100 mg kg(-1)), and the CQM low-dose (35 mg x kg(-1)) and CQM high-dose (70 mg x kg(-1)) groups. The mechanical allodynia test was adopted to evaluate the pain behavior of rats, and reflect the efficacy with the mechanical withdrawal thresholds. The rat striatum extra-cellular fluid was collected by brain micro-dialysis. The Glu level of samples was measured by high performance liquid chromatography-fluorescene detector (HPLC-FLD).

RESULTCompared to the control group, the threshold of the mechanical allodynia of the IoN injury group was decreased significantly (P < 0.05), and the concentration of Glu was increased dramatically (P < 0.05). Compared to the model group, the mechanical allodynia of photochemically-induced prosopalgia model rats increased significantly (P < 0.01), with a notable increase in brain Glu concentration (P < 0.05). Compared with the model group, all of mechanical withdrawal thresholds increased. Among them, the CQM high-dose group showed a remarkably growth at three time points (P < 0.05), with the maximum up to (23 +/- 7.3) g. And the gabapentin group showed a remarkably growth at two time points (P < 0.05), with the maximum up to (20.5 +/- 9.2) g. All of the drug groups showed significantly lower Glu concentrations in rat brains than the model group (P < 0.05).

CONCLUSIONCQM can ease the mechanical allodynia of photochemically-induced prosopalgia model rats. Its analgesic effect may be related to the decrease of Glu concentrations in striatum extra-cellular fluid.