Gate control theory

from Wikipedia, the free encyclopedia

The control barrier theory or English Gate Control Theory is a pain theory developed by Ronald Melzack and Patrick David Wall in 1965 , which represented a synthesis of the older intensity theory (summation theory) and the specificity theory of pain and had a revolutionary effect in pain research. Later some details - for example anatomical - were corrected.

The theory accepted the existence of pain receptors ( nociceptors ) and postulated that emanating from them thin are connected C-fibers in the spinal cord with the thicker A-fibers at the gateway (English gate ) acting cells (in the substantia gelatinosa of the dorsal horn of the spinal cord), which in turn control switching cells (transmission cells according to Melzack, Wall) in the spinal cord, which transmit the signal to the brain. The A and C fibers also have synapses with the transmission cells. The A-fibers have an inhibitory effect on the Tor cells, while the C-fibers have a stimulating effect. The goal can also be affected by descending fibers. They were able to explain that pain (transmitted via the C-fibers) could be suppressed by intense sensory impressions (A-fibers) and also by signals from the brain (descending fibers). If the pain stimulus is sufficiently strong, the inhibition at the gate is overcome. The original theory was later corrected because the model contained errors and over-simplifications.

According to the modern version of the theory, external and internal pain stimuli are picked up by pain receptors ( nociceptors ) in the skin, muscles, joints and internal organs. These are connected to the second neuron of the pain pathway in the dorsal horn of the spinal cord ( Rexed zones I, II and V) . Since here many neurons from the periphery converge on a single neuron , one speaks of a wide dynamic range neuron (WDR neuron). This connection is subject to very strong modulation by other neurons:

The central mechanism of action of the opioid analgesics ( morphine , fentanyl , buprenorphine , codeine and many others) that are very frequently used in clinics is based on the gate control theory.

As early as 1965 Melzak and Wall were able to show that the transmission of pain impulses in the spinal cord can be inhibited by both peripheral and descending pathways from the brain. The organism has its own pain control system, which is more or less active individually and depending on the situation. In their gate control theory, they clarified the influence of the brain on peripheral pain perception. For example, in the event of very strong emotional excitement or major injuries (e.g. in a car accident), the person concerned initially does not notice the pain via the gate control mechanism and fades it out. The analgesic effects of acupuncture , hypnosis , autosuggestion , placebos , etc. can also be explained by this theory.

An important aspect of the theory is that it can explain why patients report very different pain intensities after the same interventions. The gate control theory can also be demonstrated in everyday life. If there is pain inside the body, this can be masked by an external pressure pain on a nearby skin surface. For arm pain (caused by a fracture), for example, by applying pressure to the arm, for abdominal pain by applying pressure to the abdominal wall.

The gate control theory led to therapeutic approaches and experiments on the stimulation of peripheral nerves with implanted electrodes (Wall, Sweet 1967) and spinal cord stimulation (SCS, spinal cord stimulation, Shealy et al. 1967). After a skeptical reception, these applications brought about the actual breakthrough of the theory.

literature

Individual evidence

  1. ↑ Brian Simpson, Björn Meyerson, Bengt Linderoth, Spinal cord stimulation, in: Stephen B. MacMahon, Martin Koltzenburg (Eds.), Wall and Melzack's Textbook of Pain , Churchill-Livingstone, 5th edition 2006, p. 563. They point out also points out that the first attempts at pain therapy with electrodes, independently of the gate control theory, were made in 1960 by Mazars and colleagues in Paris.