SPLANCHNIC PROJECTION TO ORBITAL CORTEX OF CAT

In this work, a cortical representation of the splanchnic nerve on the orbital cortex of the cat has been demonstrated. 1. (1) In cats under chloralose, Nembutal or local anesthesia, stimulation of the central end of the splanchnic nerve induced short latency diphasic positive-negative responses on the orbital gyrus. 2. (2) The splanchnic responses of the orbital cortex has similar properties than the splanchnic responses of the primary areas SI-SII such as their short recovery cycles and their localisation on the field of representation of the thoracic wall; however, the extent of the cortical area of splanchnic representation was the largest on the orbital gyrus. 3. (3) Simultaneous recordings of orbital responses with both splanchnic nerve volleys and splanchno-intercostal discharges have shown that the splanchnic messages to the orbital cortex are mainly originated in the slow conducting myelinated fibers of the Aγδ group. The possibility of a projection of the fast conducting Aβ group of fibers has also been considered. 4. (4) The messages from the contralateral splanchnic nerve were found to relay in the posterior ventral nucleus of the thalamus ipsilateral to the orbital cortex; they were situated in the anterolateral columns of the spinal cord, and joined the contralateral medial lemniscus at the mesensephalic level. This strongly suggests that they followed the trajectory of the non-relayed spino-thalamic tract. 5. (5) Viscero-somatic interactions have also been studied. The splanchnic area of representation is caudal to the vagal area, but these two visceral foci overlap largely; on this common zone of visceral representation, somato-visceral, and vago-splanchnic convergence were found at the unitary level. 6. (6) The possible significance of this splanchnic orbital projection has been discussed. © 1969.