Superficial Dorsal Horn Neurons in the Rat Responsive to Visceral and Cutaneous Inputs

Abstract

The superficial dorsal horn is widely acknowledged as important to the processing of nociceptive information. As documented in this volume, fine afferent nerve fibers terminate in laminae I and II_o and second order spinal neurons upon which many of these afferents terminate transmit the received message supraspinally. Our current understanding of spinal nociceptive transmission arises primarily from investigations of afferent fibers arising from cutaneous structures. Relatively less is known about afferents arising from deeper structures, particularly viscera. Investigations of visceral afferent projections to the spinal cord describe terminals in the superficial dorsal horn (Cervero and Connell, 1984; DeGroat, 1986) and spinal units in the superficial dorsal horn respond to electrical stimulation of visceral afferents (Blair et al., 1981; Takahashi and Yokota, 1983; Cervero and Tattersall, 1987). In the present study in the rat, colorectal distension was used as a natural visceral stimulus to examine the response characteristics and convergent cutaneous receptive fields of neurons in the thoracolumbar spinal cord.