Ascending spinal pathways mediating somato-cardiovascular reflexes.

The influence of spinal somatic afferent pathways upon cardiovascular parameters were studied in anesthetized and conscious dogs. Previous studies on anesthetized cats indicated that activation of somatic A afferent fibres results in a depressor response mediated by ascending spinal pathways in the dorsolateral funiculus (DLF). Additional activation of somatic C afferent fibers results in a pressor response mediated by pathways in the region of the dorsolateral sulcus (DLS). In anesthetized dogs sympathetic-mediated cardiovascular responses to somatic afferent stimulation are found to be conducted in the DLS. To test the possibility that these afferent pathways may mediate cardiovascular responses to exercise, dogs instrumented for blood pressure and heart rate monitoring were trained to run on a treadmill on all 4 legs and on their hindlegs only. Lesions on the DLS and a portion of the DLF significantly altered heart rate responses to treadmill running on all 4 legs. These data suggest that somato-autonomic reflexes participate in the cardiovascular adjustments which occur during exercise.