PAIN-GATE THEORY

SUMMARY

1. In 1965 Melzack and Wall hypothesized an electrophysiological dorsal horn gating mechanism whereby nociceptive input could be inhibited by segmental non-nociceptive Aβ input.

2. It is further modulated by descending spinal and supraspinal influences.
3. The superficial dorsal horn has a dense glycinergic and GABAergic intrinsic innervation mediating a resting inhibitory tone through hyperpolarizing Cl^- currents.

4. Potentiation of these mechanisms (eg spinal administration of GABA_A agonists such as midazolam) produce analgesia whereas, GABA_A or glycine antagonists produce hyperalgesia & pain behaviour.

5. Central disinhibition contributes to peripheral neuropathic pain mechanisms following peripheral nerve injury.

Reference(s)

Hudspith, M.J. (2019). Anatomy, physiology and pharmacology of pain. Anaesthesia & Intensive Care Medicine, 20(8), pp.419–425. doi:https://doi.org/10.1016/j.mpaic.2019.05.008.
Cifu, D.X. (2020). Braddom’s physical medicine and rehabilitation. Elsevier. Get it on Amazon.
Cuccurullo, S. (2019). Physical medicine and rehabilitation board review. New York: Demosmedical. Get it on Amazon.
O’Young, B., Young, M.A. and Stiens, S.A. (2008). Physical Medicine and Rehabilitation Secrets. Mosby. Get it on Amazon.