Convergence of visceral and cutaneous input onto spinothalamic tract cells in the thoracic spinal cord of the cat

Abstract

Spinothalamic tract cells in the thoracic spinal cord of the cat were examined for responses to electrical stimulation of the ipsilateral greater splanchnic nerve and natural cutaneous stimulation. Tract cells were identified by antidromic activation from the contralateral brainstem at the mesencephalic-diencephalic junction. The locations of stimulating points in the brain stem and recording sites in the spinal cord were determined histologically. Spinothalamic tract cells were found in Rexed's laminae IV, V, VII, and VIII. Convergence of visceral and cutaneous input was observed in each neuron. Activity elicited in spinothalamic tract cells by excitation of A-gamma-delta visceral afferents and by noxious and non-noxious mechanical stimulation of the skin was observed. Visceral afferent input can therefore be relayed to the thalamus via direct spinal projections, and convergence of visceral and cutaneous input onto spinothalamic tract cells may play a role in the phenomenon of referred pain.