Ascending spinal pathways for somatoautonomic reflexes in the anesthetized dog

The ascending spinal pathways mediating pressor and heart rate responses to somatic afferent stimulation and induced exercise were studied in pentobarbital- and alpha-chloralose-anesthetized dogs. Bilateral sciatic nerve stimulation and induced exercise, via lumbosacral ventral root stimulation, produced pressor and heart rate responses that were blocked by bilateral dorsolateral sulcus (DLS) lesions of the lumbar spinal cord (L1-L3). Baroreceptor-mediated bradycardia were attenuated by sciatic stimulation but not by induced exercise. This attenuation was blocked by combined dorsolateral funiculus (DLF) and DLS lesions. Induced exercise with vascular occlusion to the muscle augmented the pressor and heart rate responses to exercise. These responses were blocked by combined DLS and DLF lesions. Such lesions did not influence responses to bilateral carotid occlusion, indicating that descending autonomic pathways were intact. Therefore, ascending spinal pathways mediating somatocardiovascular reflexes in anesthetized dogs are located in the lateral funiculus, extending from the dorsal root entry zone to a position somewhat ventral to the dentate ligament.