The aim of this study was to investigate the development of neuropathic pain by radiofrequency thermocoagulation on a rat infraorbital nerve (IoN).

Male Sprague-Dawley rats (n = 35) were divided into three groups, consisting of the S, T and sham operation. In the experimental groups, rats were thermocoagulated by subjecting them to 70℃ for 60 sec (S group, n = 12) or 20 sec (T group, n = 11) on IoN. In the control group (sham operation, n = 12), IoN was not thermocoagulated. The ipsilateral grooming count and escape threshold by von Frey filament (mechanical allodynia) was measured at 1, 3, 5, 7, 9, 11, 13 postoperative days. After two weeks, a 5% formalin solution was injected into the rat upper lips and grooming time was measured for 45 minutes.

Grooming count and mechanical allodynia significantly increased in the thermocoalgulation groups (S and T groups) compared to control group (sham operation) for the postoperative days. Nerve injury by radiofrequency thermocoagulation enhanced the grooming time after formalin injection in the rat upper lips.

These results lend support to the hypothesis that thermal injury using radiofrequency thermocoagulation can induce neuropathic pain in rat IoN and this type of nerve injury increases the responsiveness of chemical nocieptive stimuli.