Physiological mechanisms activated by stimulation of the spinal dorsal columns

Abstract

The gate theory (9) proposes that activity in large diameter primary afferents inhibits inputs from small diameter primary afferents. As noxious sensation is transmitted by fine fibres, any method of activating large fibre inputs to the appropriate segment of the spinal cord should reduce the perception of pain. This theory has generated immense interest during the last three decades and support for the proposal has come from many lines of study. Perhaps the most striking is the observation that stimulation of the dorsal columns is useful in the clinical treatment of several painful conditions (24). Collaterals from the large diameter primary afferent fibres ascend in the dorsal columns to terminate in the gracile and caudate nuclei. It is thought that the stimulation of these fibres sets up action potentials that pass antidromically down the columns to enter the spinal cord and operate the gating mechanism described above.