抄録
Purpose: To establish an experimental numbness model in humans, the evoked subjective sensation and CDT (current detection threshold) by compression of upper arm were examined. Methods: Healthy volunteers with informed consents were used (n=8, 25.5±4 years). Ischemic compression was applied to the arm with tourniquet (200mmHg, 15-20min). Nature of the subjective sensation was recorded and its intensity was monitored by electronic VAS device continuously. The CDT was measured by three different frequencies (5, 250, 2000 Hz) of sine waves applied to the index finger with a pair of surface gel electrodes. The frequency was randomly changed at intervals of 30 sec, and the current intensity was recorded (Geosense, Japan). Results: Clear reproducible subjective numbness sensation was evoked after the cessation of the compression and it lasted for about 15 min in VAS. The baseline CDTs were 5 <250 <2000Hz. After the compression, significant increases of CDT were observed in 250 and 2000 Hz (baseline vs. after, P<0.01, Dunnett's multiple test). Discussion: The sine wave stimulation of 5, 250 and 2000 Hz were assumed to activate C, A-delta and A-beta fibers, respectively. The production of numb sensation was accompanied with the significant increases of CDT of 250 and 2000Hz after the releases of compression. These results might be explained, at least in part, by the interaction of ectopic firing elicited by re-perfusion and current stimuli in the A fibers. [J Physiol Sci. 2008;58 Suppl:S161]
