Older theory. Introduced by melzack & wall in 1965 the authors proposed that both thin (pain) and large diameter (touch, pressure, vibration) nerve fibers carry information from the site of injury to two destinations in the dorsal horn of the spinal cord, and that the more large fiber activity relative to thin fiber activity at the inhibitory cell, the less pain is felt.
Melzac and McGill. Dr. Melzac formulated the hypothesis that only so many signals, including pain, can travel from the periphery, to the spinal cord, and to the brain. This has been the basis for sending other signals from the body by transdermal electric stimulation. Most physiologists ascribe to this idea, at least in part.