Responses of neurons in nucleus ventralis posterolateralis of the cat thalamus' to hypogastric inputs.

Recordings were made from 68 units in the nucleus ventralis posterolateralis (VPL) of the cat thalamus, which responded to stimulation of hypogastric afferents. These units also received nociceptive inputs from the contralateral integument. Units which responded exclusively to hypogastric afferent inputs were not found. Thirty seven of the units were nociceptive specific (NS), and the remaining 31 were wide dynamic range (WDR) units. All of these units were located in the shell region of the lateral subdivision of the caudal VPL. NS units responding to hypogastric afferent inputs had a circumscribed cutaneous receptive field on the contralateral abdomen, gluteal region, tail or hind limb. These areas corresponded to tactile dermatomes T13-S2. Similarly, the cutaneous receptive fields of WDR units receiving hypogastric afferent inputs were distributed in the contralateral abdomen, gluteal region, tail and hind limb, with the sole exception of one unit, whose receptive field also included a part of the lower thorax. These findings extend the previous findings that the shell region of the caudal VPL of the cat thalamus constitutes a thalamic link in a visceral pain pathway, and that the visceral and cutaneous pathways share a common projection locus in the VPL.