Constructing and deconstructing the gate theory of pain

Abstract

The Gate Theory of Pain, published by Ronald Melzack and Patrick Wall in Science in 1965, was formulated to provide a mechanism for coding the nociceptive component of cutaneous sensory input. The theory dealt explicitly with the apparent conflict in the 1960s between the paucity of sensory neurons that responded selectively to intense stimuli and the well-established finding that stimulation of the small fibers in peripheral nerves is required for the stimulus to be described as painful. It incorporated recently discovered mechanisms of presynaptic control of synaptic transmission from large and small sensory afferents which was suggested to “gate” incoming information depending on the balance between these inputs. Other important features included the convergence of small and large sensory inputs on spinal neurons that transmitted the sensory information to the forebrain as well as the ability of descending control pathways to affect the biasing established by the gate. The clarity of the model and its description gave this paper immediate visibility with numerous attempts made to test its various predictions. Although subsequent experiments and clinical findings have made clear that the model is not correct in detail, the general ideas put forth in the paper and the experiments they prompted in both animals and patients have transformed our understanding of pain mechanisms.

Pain Assessment in People With Dementia: Remaining Controversies

“…There are specific types of nerve fibers located in the peripheral sensory system responsible for the transmission of pain signals to the spinal cord and somatosensory cortex (Hugenschmidt & Sink, 2015). According to the gate theory, the physical component of pain experience caused by an external stimulus is moderated at the level of midbrain and in the spinal cord (Mendell, 2014).…”

Hypothesis: Hughlings Jackson and presynaptic inhibition: is there a big picture?

“…A key part of the gate theory was that the SG cells employed presynaptic inhibition of the sensory fibers to achieve their effects, although the possibility of additional postsynaptic mechanisms was not excluded. In the years that followed Melzack and Wall's proposal, the essential features of the gate hypothesis of pain have become generally accepted, although not without some important modifications (Mendell 2014). Importantly, the dorsal horn circuitry responsible for the gate has been shown to be more complex than originally envisaged and it is now known that postsynaptic inhibition is also involved.…”

Acupuncture therapeutic protocols for the management of temporomandibular disorders

“…The first is based on the placebo effect of the technique, which is somehow controversial, because acupuncture is effectively used also in non-suggestible beings such as animals and plants 37 . The second principle is based on Mendell's control gate theory 38 and the third principle involves the descending release by the central nervous system of hormones and neurochemical substances such as steroids, endorphin, serotonin and other natural analgesics 39 . The biggest problem of current scientific studies using acupuncture as treatment is primarily based on the Western theory of creating therapeutic protocols for each case.…”