Abstract
Histochemical procedures show a concentrated zone of phosphomonoesterase activity in the substantia gelatinosa of mouse spinal cord which represents at least two enzymic activities. At pH 7,5'-nucleotidase activity is observed in both somata and neuropil, while at pH 5 the reaction is evident only in somata. An acid phosphatase of unknown specificity is seen in somata only and exhibits optimal activity near pH 5. No comparable enzymic reactions are observed in cat spinal cord sections. Electron microscopic studies demonstrate separate cytologic distributions of the two enzymic activities in substantia gelatinosa. With nucleotides, the reaction is confined to boundaries of processes within the neuropil and to nuclei at pH 7. At pH 5 using an acid phosphatase substrate, β-glycerol phosphate, slight reactions were noted within nerve fibers. Use of β-glycerol phosphate near pH 7 demonstrates both types of activity simultaneously, the boundary reactions typical of the nucleotidase and the reactions within axons and dendrites characteristic of the phosphatase.