Responses of spinothalamic tract cells in the thoracic spinal cord of the monkey to cutaneous and visceral inputs.

Somatovisceral convergence was demonstrated in recordings from 15 of 16 spinothalamic tract cells in the lower thoracic spinal cords of anesthetized monkeys. Inputs were produced by mechanical (or sometimes electrical) stimulation of the skin over the lower trunk and by electrical stimulation of the greater splanchnic nerve through a buried electrode. The volley in the greater splanchnic nerve was monitored using a buried electrode on the sympathetic chain. Spinothalamic tract cells could be excited by activity in A delta and C fibers, but no effects produced by A beta fibers were noted. In some cases inhibitory effects were observed due to movement of hair on the trunk, and inhibitory interactions could be demonstrated between cutaneous and visceral afferent volleys.