Developing concept of the gating mechanisms in pain perception.

A short review of the main trends in neurophysiological research of the gating mechanism of pain perception is presented. The original model of Melzack and Wall has been modified in two aspects. First - postsynaptic inhibition and increased concentration of potassium ions in the extracellular space play a role in the modulation of impulse transmission at the segmental level of the spinal cord. Second - serotoninergic descending pathways originating in the medial structures of the brain stem which are very sensitive to narcotics contribute to the modulation of synaptic transmission from nociceptors.