Distribution of axons showing both enkephalin- and serotonin-like immunoreactivities in the lumbar cord segments of the Japanese monkey (Macaca fuscata).

Axons exhibiting both enkephalin- and serotonin-like immunoreactivities were observed by the double immunofluorescence method in the lumbar cord segments of the Japanese monkey. Double-labeled axons were seen almost exclusively in the dorsal horn, particularly in lamina I, lamina IIa and the lateral part of lamina V. After thoracic cordotomy, almost all of the double-labeled axons disappeared from the lumbar cord segments.