ACTIVATION OF CCK-A RECEPTORS INDUCES ELEVATION OF PLASMA-CORTICOSTERONE IN RATS

Cholecystokinin octapeptide (CCK-8) and ceruletide (1-mu-g/kg) produce d a pronounced increment of plasma corticosterone levels at 30 min aft er intraperitoneal administration. The response to these peptides was suppressed by pretreatment with a selective antagonist for CCK-A recep tors, (-)L-364,718, in a dose-related manner, but not with an antagoni st for CCK-B receptors. (+)L-365,260. However. (-)L-364,718 itself had no effect on basal levels of plasma corticosterone. These results ind icate that peripheral administration of CCK-8 and ceruletide stimulate s the hypothalamo-pituitary adrenal axis through the activation of CCK -A receptors, but not CCK-B receptors.