The Neural Pathways for the Hypothetic Nociceptive-Sympathetic Coupling

What is it about?

In May 2016, it was suggested by the US athletes playing games of National Basketball Association (NBA) in television that the pain sensation might result from the post-sensory nociceptive-sympathetic coupling. In this review, it is attempted to newly delineate the underlying neural pathways for this post-sensory nociceptive-sympathetic coupling. Based on the contemporary feedback neural circuits of pain transmission in spinal cord, it is summarized that the Aδ- and C-fibers relay the sensory noxious signals to the laminae I, II and V of dorsal spinal horn, and in turn activate the periaqueductal grey(PAG) in midbrain, which feedbacks via raphe to inhibit the nociceptive transmission of spinal cord. Herein it is newly added that, as extension of the contemporary feedback pain circuits, the neurons in laminae I and V of dorsal spinal horn as well as those in PAG can additionally activate the sympathetic outputs, completing the post-sensory nociceptive-sympathetic coupling. It is emphasized that such nociceptive-sympathetic coupling would contribute at least partially to the pain sensation because of sympathetically maintained pain. It is also pointed out that the neurons in parabrachial area(PB) can concurrently relay the nociceptive inputs from spinal cord while regulating the respiration, coordinating the nociceptive and respiratory activities during pain sensation. Because both PAG and PB are below thalamus, it is speculated that these sympathetic and respiratory associations with pain are primitive and universal in evolution in vertebrates. It is expected to promote this hypothesis to revise the pain mechanisms in vertebrates and the relevant investigations in future.

Featured Image

Photo by Katherine Hanlon on Unsplash

Photo by Katherine Hanlon on Unsplash

Why is it important?

The formulated neural pathways are new, alternative to the presently widely accepted ascending nociceptive pathways.

Perspectives