SCIATIC CRYONEUROLYSIS IN RATS - A MODEL OF SYMPATHETICALLY INDEPENDENT PAIN .1. EFFECTS OF SYMPATHECTOMY

The purpose of this study was to evaluate the effects of preemptive an d postlesion sympathectomy in the sciatic cryoneurolysis (SCN) model o f neuropathic pain in rats. SCN in rats produces a prolonged significa nt mechanical allodynia (hypersensitivity to previously non-noxious me chanical stimuli) with no thermal hyperalgesia. In at least two other models, sympathectomy is effective in attenuating existing mechanical allodynia and thermal hyperalgesia or deterring their development afte r nerve injury. These models appear to mimic the direct sympathetic in volvement characteristic of the clinical syndrome termed sympathetical ly maintained pain (SMP). To investigate these concepts in the SCN mod el, sympathectomy was performed prior to SCN in animals with establish ed SCN-induced allodynia. Sympathectomy did not alter the pattern of e xisting allodynia or its development in this model. The results sugges t that SCN is a useful and easily reproducible model of sympatheticall y independent pain (SIP).