Whole body autoradiography of CCK-8 in rats.

Rats were given i.v., intranasal or intraperitoneal doses of CCK-8 (sulfated) labelled with 125I-labeled Bolton and Hunter reagent. Radioactivity was found mainly in the liver, kidney, and the intestinal contents. No radioactivity was detected in the brain. In animals dosed i.v., specific localization occurred in the tissue of the pyloric region of the stomach, and in the pancreas. Label persisted within the pyloric region of the stomach for longer than 30 min, in spite of the reported half-life of CCK-8 in plasma of approximately 1 min. Intranasal and intraperitoneal doses had limited bioavailability. The binding to the sites in the pyloric region of the stomach, which required systemic delivery, may have identified receptors associated with appetite control.