Rodent model of chronic central pain after spinal cord contusion injury and effects of gabapentin

Spinal cord injury (SCI) often results in abnormal pain syndromes in patien ts. We present a recently developed SCI mammalian model of chronic central pain in which the spinal cord is contused at T8 using the NYU impactor devi ce (10-g rod, 2,0-mm diameter, 12,5-mm drop height), an injury which is cha racterized behaviorally as moderate. Recovery of locomotor function was ass essed with an open field test and scored using the open field test scale (B BB scale). Somatosensory tests of paw withdrawal responses accompanied by s upraspinal responses to both mechanical punctate (von Frey hairs) and nonpu nctate (4 mm diameter blunt probe) as well as thermal (radiant heat) periph eral stimuli were performed. Comparisons at the level of the individual ani mal between precontusion and postcontusiom responses indicated significant increases in reactions to low threshold punctate mechanical stimuli, non-pu nctate stimuli and thermal stimuli (p < 0,05), To demonstrate the validity of this model as a central pain model, gabapentin, an agent used clinically for central pain, was given i.p, at 10 or 30 mg/kg, Gabapentin treatment s ignificantly and reversibly changed the responses, consistent with the atte nuation of the abnormal sensory behavior, and the attenuated responses last ed for the duration of the drug effect (up to 6 h), These results support t he use of the spinal contusion model in the study of chronic central pain a fter SCI.