Thoracic visceral inputs use upper cervical segments to inhibit lumbar spinal neurons in rats

We tested the hypothesis that cardiopulmonary sympathetic afferent (CPSA) input entering upper thoracic spinal segments relays in the cervical spinal cord to inhibit activity of lumbar spinothalamic tract (SST) cells and dorsal horn (DH) cells. Two sequential spinal transections in the same animal were made, one at rostral C1 and one at C4-C6 segments, to determine neuronal pathways involved in the inhibition. We concluded that inhibitory effects induced by CPSA and somatic stimulation might be mediated by propriospinal mechanisms located in upper cervical segments. Vagal inhibition required supraspinal pathways.