Excitatory and inhibitory electrodermal reflexes evoked by cutaneous stimulation in acute spinal cats

The electrodermal reflex (EDR) was recorded from the paws of acute spinal cats by a DC potential recording method. The EDR was produced either by pinching the skin in various areas of the trunk, or by electrical stimulation of cutaneous afferents of various spinal segments. It was found that not only excitatory but also inhibitory EDRs were produced and that occurrence of the excitatory and inhibitory EDRs depended on both the segmental position and the laterality of the stimulated area. Cutaneous stimulation generally produced excitatory EDRs more frequently than inhibitory ones, except when afferent inputs entered the spinal cord at or close to the segments of sudomotor outflow; in the latter case inhibitory EDRs were comparatively frequent and strong. Maximal inhibitory EDRs were elicited by stimulation of the group II afferent fibers of the cutaneous nerves only, whereas maximal excitatory EDRs were elicited after stimulation of the group II, III and IV afferent fibers of cutaneous origin.