using the methods of immunocytochemistry and radioimmunoassay , five peptides ( vasoactive intestinal polypeptide ( vip ) , substance p , somatostatin , met-enkephalin , and bombesin ) have been found in the gall bladder and the biliary tracts of guinea pig and each of them possesses a characteristic distribution pattern .
C0016976
gall bladder
C0005423
biliary tracts