Peripheral and central effects of CCK receptor agonists on operant feeding in pigs.

Operant feeding was recorded in 18 h deprived pigs after peripheral (IV) or central (ICV) administration of saline, the CCK A agonist A-71378, the CCK B agonist pentagastrin, or pentagastrin vehicle. In Experiment 1 (n = 10), A-71378 (0.5, 1.0, and 2.0 micrograms/kg) given IV produced a sustained dose-related reduction in food intake (p < 0.02), whereas the same doses of pentagastrin were without effect. In Experiment 2 (n = 10), neither agonist given ICV (1 microgram) had consistent effects on operant responding. A higher ICV dose of A-71378 (5 micrograms) was also ineffective, whereas 1 microgram CCK octapeptide given ICV inhibited feeding (p < 0.03). These findings suggest that A receptors outside the blood-brain barrier mediate the suppressant effect of IV CCK on feeding in the pig and that neither peripheral nor central B receptors influence food intake in this species.