We have reported in our previous studies that stimulation of the spla- nchnic nerve evoked unit discharges in thalamic PO nucleus of cat which showed the characteristics of pain discharge. The present paper further stu- died the relationship between A-fiber afferent impulse of splanchnic nerve and the evoked discharges of PO nucleus. Experments were carriedout on 11 cats immobilized witb flaxedil under artificial respiration. Unit discharges were recorded by glass microelectrode (1-2μ) from PO nucleus and t...