Experiments were performed on cats under chloralose and flaxedil。 The splanchnic nerve was stimulated with electric pulses of various intensities and blocked by a polarizing current so as to excite different kinds of fibers(Aβ

Aδ

C)。The averaged evoked potentials were recorded in the contralateral somatosensory cortex(CEP). Aβ-CEP evoked by Aβ fiber input showed a primary positive wave; Aβδ-CEP elicited by Aβ and Aδ fiber inputs showed a primary response and a secondary response

late component;Aε-CEP by Aδ fiber input showed a secondary and late response.These results indicated that the primary response of A-CEP was evoked by Aβ fiber input

and the secondary and late response by Aδ fiber.AC-CEP by A-and C-fiber inputsappeared similar to Aβδ-CEP.It was suggested that C fiber input might be inhibited by A fiber input and did not participate in AC-CEP. After blocking the A fiber by a polarizing current

a stimulus above C fiber threshold would cause a particular C-CEP

and the amplitude depended on the amount of afferent C volley. From the above results we tend to believe that all of the fiber inputs (Aβ

Aδ

C)may reach the somatosenory cortex and elicit CEP

and that C-CEP reflecting C fiber input accurately may be a suitable index for visceral pain

and AC-CEP only reflects the A fiber input but not the C fiber.