Researchers from the Institute of Pharmacology and Toxicology at the University of Zurich have gained new insight into the mechanism of pain transmission first proposed 50 years ago as the “Gate Control Theory.” Wall and Melzack proposed the existence of inhibitory nerve cells in the spinal cord that determine whether or not a pain impulse coming from the periphery, such as the foot, is relayed to the brain. The study team, writing in the journal Neuron, assert that these control cells are located in the spinal dorsal horn and use the amino acid glycine as an inhibitory messenger.
Using genetically modified viruses, the team demonstrated the ability to affect the function of these neurons in mice. Disabling the glycine-releasing neurons lead to an increased sensitivity to pain and signs of spontaneous pain. Activating them produced mice that were less sensitive to painful stimuli than their untreated counterparts. The UZH researchers were able to verify a further hypothesis of the Gate Control Theory by confirming that the inhibitory, glycine-releasing neurons are also innervated by light touch to sensitive skin nerves. The journal abstract, with link to the full article, may be read here.