Immunocytochemical evidence for the presence of met‐enkephalin and leu‐enkephalin distinct neurons in the brain of the elasmobranch fish Scyliorhinus canicula

Immunohistochemical methods have been used to investigate the distribution of various opioid peptides derived from mammalian proenkephalin in the central nervous system of Scyliorhinus canicula. The results indicate that both Leu‐ and Met‐enkephalin‐immunoreactive peptides are present in the dogfish brain. In contrast, enkephalin forms similar to Met‐enkephalin‐Arg‐Phe or Met‐enkephalin‐Arg‐Gly‐Leu, and mammalian α‐neo‐endorphin, dynorphin A (1–8), dynorphin A (1–13), and dynorphin A (1–17) were not detected.