DAILY SPINAL-CORD STIMULATION SUPPRESSES AUTOTOMY BEHAVIOR IN RATS FOLLOWING PERIPHERAL DEAFFERENTATION

Autotomy in experimental animals following peripheral nerve section ha s been interpreted as a sign of pain corresponding to the chronic pain observed in patients with extensive nerve lesions. Such pain may be a lleviated by spinal cord stimulation. In the present study, the effect of such stimulation, via chronically implanted electrodes, on autotom y behavior following sciatic nerve section was assessed in the rat. Th e stimulation was applied for 30 min daily during a 10-day period. The re were four groups of animals, 16 in each, half of them females. Stim ulating electrodes were implanted in all and one group served as contr ol, receiving sham stimulation. In one group, the stimulation was star ted when autotomy was observed, one received stimulation from the day of nerve section, and in one it was begun three days before section. T he onset of autotomy was significantly delayed in the latter two group s. When stimulation was applied as ''treatment'', autotomy ceased but reappeared after the 10-day stimulation period. The incidence and seve rity of autotomy was markedly delayed and reduced when the stimulation had been applied just after the nerve section or before. In the latte r groups, the diminished degree of autotomy persisted for the entire o bservation period, lasting 60 days after the stimulation was stopped. It seems that spinal cord stimulation, albeit applied only once daily and during a limited time period, can protect the spinal cord from dev eloping the state of hyperexcitability believed to be the major cause of autotomy behavior. Peripheral mechanisms map also play a role by th e antidromic activity evoked by the stimulation in the sectioned perip heral nerve. This study shows that spinal cord stimulation, which is a commonly employed method for treating chronic neurogenic pain, may ha ve long-lasting effects on plasticity changes in the spinal cord follo wing peripheral nerve injury, even when the stimulation is applied for short periods of time. Copyright (C) 1996 IBRO.