Distribution of human leumorphin-like immunoreactivity in the monkey spinal cord revealed by immunocytochemistry

The regional distribution of human leumorphin (HL)-like immunoreactivity (HL-LI) in monkey (Macaca fuscata) spinal cord and dorsal root ganglia was investigated by peroxidase-anti-peroxidase immunocytochemistry using specific antiserum. HL-LI-positive fibers and terminals were distributed densely in laminae (Rexed) I and II, and sparsely in laminae III-VII and X, but no immunoreactive elements were observed in the ventral horn, the white matter or the dorsal root ganglia. Many immunoreactive neuronal perikarya were found in laminae I and II. Intrathecal injection of colchicine also revealed the presence of immunoreactive neuronal perikarya in laminae III-VII and X. These results suggest the presence of HL-LI, which represents HL and/or its C-terminal fragment, in the neuronal elements of the monkey spinal cord.