Cholecystokin in - octapeptide ( cck - 8 ) is a kind of endogenous brain - gut peptide . recent studies suggest a regulatory function of cck - 8 in the immune system 八肽胆囊收缩素( cholecystokinin - octapeptide , cck - 8 )是一种内源性的脑肠肽,近年研究表明cck - 8对免疫系统具有调节作用。