摘要

The present study investigated the effects of systemic administration of dexmedetomidine, a selective alpha 2 adrenergic receptor (alpha 2AR) agonist, and gabapentin either alone or in combination on thermal hyperalgesia evoked by ankle joint inflammation. Monoarthritis of rat ankle joint was induced by an intra-articular injection of Complete Freund's Adjuvant (CFA). The paw withdrawal latency (PWL) from a thermal stimulus was measured in awake rats. Intraperitoneal (i.p.) injection of dexmedetomidine (2.5, 5, 10 and 20 mu g/kg) or gabapentin (25, 50, 100 and 200 mg/kg) significantly and dose-dependently increased the PWL of the hindpaw ipsilateral to CFA-injected joint. The PWLs of the non-injected and normal saline (NS)-injected hindpaws were not significantly affected by the two agents at the most doses tested except the highest dose of dexmedetomidine (20 It mu g/kg). Although low dose of dexmedetomidine (2.5 mu g/kg) or gabapentin (25 mg/kg) alone did not affect or lightly increased PWLs of the hindpaw ipsilateral to CFA-injected joint, a combination of dexmedetomidine and gabapentin (2.5 mu g/kg + 25 mg/kg, or 5 mu g/kg + 50 mg/kg) significantly reversed CFA-induced thermal hyperalgesia for 60 min without sedation/motor impairment. These results provide the first identification that co-application of dexmedetomidine and gabapentin may synergistically antagonize inflammatory pain, and this might prove to be beneficial in the treatment of arthritic pain.