Pharmacological and behavioral characterization of the saphenous chronic constriction injury model of neuropathic pain in rats

The aim of the present study was to develop a new experimental pain model by adapting the chronic constriction injury (CCI) model of the sciatic nerve to the exclusively sensory saphenous nerve in rats. Animals were divided into naive, sham, and two experimental groups, in which two or four 4-0 chromic gut ligatures were loosely ligated around the saphenous nerve. Then, behavioral signs of neuropathic pain were observed for 8 weeks. In rats with four ligatures, prominent mechanical allodynia and thermal hyperalgesia developed; these behavioral signs were not prominent in rats with two ligatures. Pharmacological analysis was made in rats with four loose ligations; morphine and WIN 55,212-2, a cannabinoid agonist, reversed all of the modalities tested, whereas gabapentin only suppressed mechanical allodynia and amitriptyline only reduced mechanical hyperalgesia. Our data establish a rat model of saphenous CCI with significant allodynia and hyperalgesia, which is sensitive to a number of analgesic compounds.