Cord Dorsum Potentials Evoked by Electroacupuncture Applied to the Hind Limbs of Rats

The longitudinal distribution of the cord dorsum potentials (CDPs) produced by electro-acupuncture (EA) stimulation at acupuncture points (APs) located on the hind limbs of rats was analyzed in this study. Single electrical pulses (0.05 ms, 1 Hz) applied to the bladder (BL) and the gallbladder (GB) APs produced CDPs on several spinal segments and were composed of the following four components: an afferent volley, two negative components (N1 and N2), and one positive component (P wave). The larger evoked CDPs differed in their rostrocaudal distributions depending on the stimulated AP site, with those evoked by GB32-33 (at L3) and GB36-37 (at L4) being more caudal than those generated by BL58-59 (at L5) and BL37-38 (at L6). The CDPs produced by stimulating nonacupoints (NAPs) showed similar components and rostrocaudal distributions that were smaller in amplitude than those evoked by stimulating APs. The CDPs produced by stimulating NAPs located on a meridian acupuncture area were similar in amplitude and longitudinal distribution to those produced by stimulating APs. Our results suggest that the specificity of EA stimulation for CDPs responses is mainly related to an activation of meridian pathways associated with peripheral nerve routes rather than to a restricted point specificity of APs.