Cholecystokinin-33 acutely attenuates food foraging, hoarding and intake in Siberian hamsters

Abstract

Neurochemicals that stimulate food foraging and hoarding in Siberian hamsters are becoming more apparent, but we do not know if cessation of these behaviors is due to waning of excitatory stimuli and/or the advent of inhibitory factors. Cholecystokinin (CCK) may be such an inhibitory factor as it is the prototypic gastrointestinal satiety peptide and is physiologically important in decreasing food intake in several species including Siberian hamsters. Systemic injection of CCK-33 in laboratory rats decreases food intake, doing so to a greater extent than CCK-8. We found minimal effects of CCK-8 on food foraging and hoarding previously in Siberian hamsters, but have not tested CCK-33. Therefore, we asked: Does CCK-33 decrease normal levels or food deprivation-induced increases in food foraging, hoarding and intake? Hamsters were housed in a wheel running-based foraging system with simulated burrows to test the effects of peripheral injections of CCK-33 (13.2, 26.4, or 52.8 microg/kg body mass), with or without a preceding 56 h food deprivation. The highest dose of CCK-33 caused large baseline reductions in all three behaviors for the 1st hour post-injection compared with saline; in addition, the intermediate CCK-33 dose was sufficient to curtail food intake and foraging during the 1st hour. In food-deprived hamsters, we used a 52.8 microg/kg body mass dose of CCK-33 which decreased food intake, hoarding, and foraging almost completely compared with saline controls for 1h. Therefore, CCK-33 appears to be a potent inhibitor of food intake, hoarding, and foraging in Siberian hamsters.

Keywords: appetitive behavior; consummatory behavior; injection; satiety.

Figure 1

Mean ad libitum food intake as affected by three doses of CCK-33 (13.2, 26.4, and 52.8 μg/kg body mass), for one hour post-injection, expressed as a percent inhibition from the saline controls ± SEM: A) 10 revolutions per pellet group (saline: 1.57 ± 0.48 pellets eaten), B) Free Wheel/Free Food group (saline: 2.15 ± 0.43 pellets eaten), and C) Blocked Wheel/Free Food group (saline: 2.62 ± 0.61 pellets eaten). * P<0.05 vs saline injections.

Figure 2

Mean ad libitum food hoarding as affected by three doses of CCK-33 (13.2, 26.4, and 52.8 μg/kg body mass), for one hour post-injection, expressed as a percent inhibition from the saline controls ± SEM: A) 10 revolutions per pellet group (saline: 1.73 ± 0.44 pellets hoarded), B) Free Wheel/Free Food group (saline: 2.25 ± 1.08 pellets hoarded), and C) Blocked Wheel/Free Food group (saline: 1.46 ± 0.41 pellets hoarded). * P<0.05 vs saline injections.

Figure 3

Mean food intake post-food deprivation as affected by CCK-33 (52.8 μg/kg body mass), for one hour post-injection, expressed as percent inhibition from saline controls ± SEM: A) 10 revolutions per pellet group (saline: 4 ± 2.49 pellets eaten), B) Free Wheel/Free Food group (saline: 7.3 ± 0.67 pellets eaten), and C) Blocked Wheel/Free Food group (saline: 4.4 ± 0.93 pellets eaten). * P<0.05 vs saline injections.

Figure 4

Mean food hoarding post-food deprivation as affected by CCK-33 (52.8 μg/kg body mass), for one hour post-injection, expressed as percent inhibition from saline controls ± SEM: A) 10 revolutions per pellet group (saline: 4.7 ± 2.85 pellets hoarded), B) Free Wheel/Free Food group (saline: 10.5 ± 2.81 pellets hoarded), and C) Blocked Wheel/Free Food group (saline: 5.0 ± 3.56 pellets hoarded). * P<0.05 vs saline injections.