Abstract: In order to observe the changes of myotension in the paralyzed limbs after subcutaneous injection(S.C)of capsaicin,we observed the changes of the spontaneous Electromyography(EMG)recorded in the quadriceps femoris before and after T-5 level spinal transection and found that the amplitude of EMG kept a low level in normal rats but increased progressively after operation.After treating the animals with capsaicin 200mg/kg(S.C)in three consecutive days,we found a much lower spontaneous EMG and a much higher pain threshold than that of the controls.Radioimmunnoassay detected that the content of SP in spinal dorsal horn was reduced by 38.4%,the general condition did not severely changed during the experiment.The results indicate that SP in the spinal dorsal horn participates in the regulation of myotension,and it is suggested that subcutancous injection of capsaicin may be one effective treatment to reduce the hypermyotension in the paralyzed limbs.

Key words: substance P(SP), capsaicin, spinal transection, myotension