[Oblongata in the spinal trigeminal nucleus of the adult rat (author's transl)].

The substantia gelationsa has been noted as a region of central pain control, In 1979, we reported that an intense thiamine monophosphatase (TMPase) activity was specifically localized on the plasma membrane of the synaptic glomeruli, especially dense sinusoid axon terminals (DSA). In the present investigation, the ultracytochemical localization of TMPase activity was studied in the spinal trigeminal nucleus of the adult rat. Vibratome sections of aldehyde-fixed specimens were incubated in the incubation medium (veronal-acetate buffer, pH 5. 8, 27 mM, thiamine monophosphoric acid chloride 2mM, lead nitrate 2.7 mM, sucrose 146 mM, final pH 5.4) for 30 min at 37 degrees C, and processed for light as well as electron microscopy. At the light microscopic level, the reaction products, lead sulfide, were observed to be localized in the substantia gelatinosa of the caudal medulla oblongata in the spinal trigeminal nucleus. At the electron microscopic level, the TMPase activity was positive on the plasma membrane of DSA in the region where is particularly concerned with the relay of thermal and noxious stimuli. It has been suggested by us previously that there may be some relationship between the TMPase activity and pain, mechanism in the spinal cord, and the results that the situation seems to be hold true in the spinal trigeminal nucleus, also.