Synergistic effects of cholecystokinin isoforms (CCK4 and CCK8s) with glutamate on food intake in laying chickens

The present study was conducted with the aim of investigating the synergistic effects of CCK and glutamate on feeding behavior in layers. For this purpose. In the first experiment, the control solution, CCK4 (1 nmol), glutamate (75 nmol), and CCK4 + glutamate were injected intracerebroventricularly (ICV). The second experiment was performed according to the first experiment, with the difference that glutamate was injected with an effective dose (300 nmol). In the third experiment, the control solution, CCK8s (0.125 nmol), glutamate (75 nmol), and CCK8s + glutamate were administered. The fourth experiment was also the same as the third experiment and only the doses of CCK8s (1 nmol) and glutamate (300 nmol) were changed. According to the obtained results, the administration of doses under the effect of CCK4 and glutamate separately or simultaneously did not have a significant effect on the food intake of chickens (p<0.05). Injection of an effective dose of glutamate led to a significant decrease in feed intake, and simultaneous administration of CCK4 with glutamate did not change this hypophagic effect (p<0.05). Injection of sub-effective doses of CCK8s and glutamate had no significant effect on food intake (p<0.05), however, their simultaneous administration weakened food intake (p<0.05). Injection of effective doses of CCK8s and glutamate separately caused a significant decrease in food intake in chickens, and the administration of both of them strengthened this hypophagic effect (p<0.05). Finally, it seems that there is a synergistic effect between CCK8s and glutamate in the regulation of food intake in laying chickens.