- A phenomenon in which pain impulses, usually arising from primary visceral afferent fibers from one part of the body, terminate on dorsal horn projection neurons that normally receive cutaneous afferents from a different part of the body (such as the arm).
- It is the convergence of these distinctly different inputs onto the same projection neurons that provides the basis for this phenomenon.
- However, other theories including central sensitization, thalamic convergence, and hyperexcitability have also been proposed.
- Pain signaling in the spinal cord dorsal horn is via glutamate (C fibers and A-delta fibers) and substance P (C fibers).
- The opioid peptides (enkephalin and dynorphin) are released by inhibitory interneurons in the dorsal horns, medulla, and PAG and inhibit transmission of pain impulses.
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