Dexmedetomidine reduces neuropathic pain in a rat model of skin/muscle incision and retraction

Abstract

Dexmedetomidine has been proposed as a novel anesthetic adjuvant. However, it remains unclear whether peripheral administration of dexmedetomidine is safe and effective to reduce acute postoperative pain. This study aimed to examine the effects of dexmedetomidine on neuropathic pain. Adult male Sprague-Dawley rats were anaesthetized and randomly allocated into four groups (n=8): Groups S, R, RD1, and RD5 were injected with saline, 0.5% ropivacaine, 0.5% ropivacaine combined with 1μg dexmedetomidine, and 0.5% ropivacaine combined with 5μg dexmedetomidine, respectively, around the saphenous nerve. Then, the rats were subjected to skin/muscle incision and retraction (SMIR) surgery in the medial thigh. Mechanical and heat sensitivity was evaluated and morphology of the dorsal root ganglion (DRG) neurons was observed by electron microscopy. Some 62.5%, 50%, 12.5%, and 25% of rats developed mechanical hypersensitivity in Groups S, R, RD1, and RD5, respectively. The number of swollen mitochondria in DRG neurons was significantly more in Group S (257.2±60.9) and Group R (291.6±82.1) than in Group RD1 (97.2±33.3) and Group RD5 (13.6±17.9). In addition, the edema in endoplasmic reticulum and Golgi apparatus was decreased in Group RD1 and Group RD5 compared with Group S and Group R. Peripheral administration of dexmedetomidine improves mechanical and heat hyperalgesia and mitigates postoperative pain.