Objective: To observe the analgesic effect of CQM on photochemically-induced prosopalgia model rats, and discuss its impact on the exciting amino acid neurotransmitter-glutamate (Glu).
Method: Male 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).
Result: Compared 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).
Conclusion: CQM 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.