opiate peptides , encephalins and endorphins , originally isolated from the brain , have been detected by the immunocytochemistry and radioimmunoassay in the digestive system and localized in the distinctive endocrine-paracrine cells of apud series of the gastrointestinal mucosa and the nerve fibers of the myenteric plexus .
C0205753
opiate peptides
C0014242
endorphins