Alpha-neo-endorphin coexists with dynorphin-A(1-8) within intramurally lying perikarya of rat duodenum.

By the use of the immunofluorescent microscopic staining technique, adjacent serial sections through the rat duodenum were alternately stained with specific antisera directed to the opioid peptides alpha-neo-endorphin and dynorphin-A(1-8). alpha-Neo-endorphin immunoreactivity has been revealed exclusively within perikarya lying intramurally in the longitudinal muscle layer. These alpha-neo-endorphin and dynorphin-A(1-8) immunoreactive perikarya were large in diameter, round in shape, contained a large and round nucleus, and were recognized only occasionally there. alpha-Neo-endorphin immunoreactivity was coexistent with dynorphin-A(1-8)-positive material within these perikarya. Since no alpha-neo-endorphin material was detected within duodenal nerve fibres and terminals, it might be concluded that this peptide is further enzymatically cleaved to the opioid pentapeptide Leu-enkephalin during its axonal transport from intramural perikarya to nerve terminals and during its storage there.