Immunohistochemical localization of enkephalin-like substance in the central nervous system of the amphioxus

The localization of enkephalin-like materials in the central nervous system of the amphioxus, Branchiostoma belcheri, was studied by immunohistochemical techniques, employing antisera raised in rabbit against synthetic methionine-enkephalin and leucine-enkephalin, respectively. The perikarya and nerve fibers showing methionine-enkephalin-like immunoreactivity were distributed widely in the brain and spinal cord. Furthermore, immunoreactive material was found to accumulate densely in localized spots, around which small tissue spaces were often seen, suggesting possible release of this substance into systemic circulation. These results suggest that this peptide has diverse functions in the amphioxus. No immunoreaction to antiserum against leucine-enkephalin was detected in the central nervous system of the amphioxus