Role of glucagon in the control of food intake in zucker obese and lean rats

Although there is strong evidence for glucagon's role in the control of food intake, the essentiality of this role remains in question. In several experiments the feeding responses to glucagon and glucagon antisera were investigated in both Zucker and Sprague-Dawley rats. Intraperitoneal injection of 400 micrograms/kg glucagon decreased 30-min food intake 18% (p less than 0.01) in Zucker lean rats and increased 30-min food intake 16% (NS) in Zucker obese rats, suggesting obese rats are less sensitive. In Sprague-Dawley rats the same dose decreased first meal size 28% (p less than 0.01), indicating that they were more sensitive than Zucker lean rats. Intraperitoneal injection of 400 micrograms/kg glucagon increased plasma glucagon concentrations in the vena cava and the tail vein 150-fold and 10-fold, thus, superphysiological doses may be required to elicit satiety. In contrast, administration of a glucagon antisera increased food intake of Zucker rats for up to 6 hr and increased meal size for 5 hr. The findings suggest that glucagon's role in control of food intake in Zucker obese and lean rats is similar, but the superphysiological glucagon changes which occur with exogenous administration indicate that glucagon may only indirectly elicit satiety.