Comparative electron histochemistry of thiamine monophosphatase and substance P in the upper dorsal horn.

The genuine marker enzyme of primary nociceptive neurons, thiamine monophosphatase (TMPase) has been localized in the substantia gelatinosa of the rat spinal cord by means of light-and electron microscopic histochemistry; localization of substance P has been studied by light-and and electron microscopic immunohistochemical methods. It has been shown that TMPase and substance P are located in two, regionally and structurally different populations of axon terminals. Substance P is contained both in A delta and in drC axons. In the postero-lateral funiculus of the white matter, substance P-positive axons establish axo-somatic synaptic contacts with large multipolar neurons of Cajal's interstitial nucleus.