IVT CCK-8 is more effective than IV CCK-8 at decreasing meal size in the baboon

In this study, we compared the effectiveness of intravenous (IV) vs. intraventricular (IVT) cholecystokinin octapeptide (CCK-8) to decrease single meal size over a dose range of 0.1 to 4.0 micrograms/kg in a population of overnight fasted baboons. IV CCK did not decrease meal size significantly at doses of 0.5, 1, and 4 micrograms/kg (84 +/- 22%, 78 +/- 12%, and 89 +/- 33% of paired control meal sizes respectively). IVT CCK significantly decreased single meal size at all doses tested (40 +/- 18%, 26 +/- 10%, 37 +/- 15%, 26 +/- 12%, and 12 +/- 6% of paired control meal sizes at 0.1, 0.25, 0.5, 1, and 2 micrograms/kg respectively). Meal suppression with IVT CCK was significantly greater than that achieved with IV CCK at doses of 1 and 2 micrograms/kg. We conclude that in the baboon, CCK may have a direct effect at the central nervous system to suppress single meal size.