Laminar localization of the sites of release of immunoreactive substance P in the dorsal horn with antibody-coated microelectrodes

The localization of the sites of release of immunoreactive substance P (SP) in the spinal cord after peripheral nerve stimulation has been examined in the anaesthetized cat. A new technique using antibodies bound to the outside of glass microelectrodes has allowed the identification of these sites with a spatial precision previously unobtainable. A basal release of SP was detected and this was not increased by electrical stimulation of large myelinated primary afferent fibres. Excitation of unmyelinated primary afferents resulted in the release of high concentrations of SP confined to the region of the substantia gelatinosa and lamina V–VI.