Effects of cholecystokinin on apomorphine-induced changes of motility in rats.

Subcutaneous injection of apomorphine in small doses decreased, while larger doses increased motility in rats. The hypomotility was abolished by intracerebroventricular administration of sulphated cholecystokinin octapeptide [CCK-8(s)], but not by non-sulphated CCK-8 [CCK-8(ns)]. In contrast, the hypermotility was not influenced by CCK peptides. An antiserum directed against the C-terminus of CCK did not affect hypermotility induced by apomorphine but suppressed the apomorphine-induced hypomotility further. The results indicate that sulphated CCK-peptides contribute to the control of motility, which can be inhibited by apomorphine.