Hepatic portal glucagon infusion decreases spontaneous meal size in rats

We describe the first tests of intraportal pancreatic glucagon infusions during spontaneous meals in undisturbed, ad libitum-fed male Sprague-Dawley rats. Two-minute infusions beginning at meal onset and delivering 14 micrograms glucagon reduced the size and duration of both early and late nocturnal meals. After glucagon infusion during early nocturnal meals, neither the latency nor the size of the next meal was affected. Meal onset infusion of 3.4-14 micrograms glucagon/meal dose-dependently reduced late nocturnal meal size 19-64%. Full-meal glucagon infusions did not inhibit feeding more than 2-min infusions begun at meal onset or meal middle, despite fivefold differences in amount infused. These data indicate that spontaneous feeding is pharmacologically inhibited by prandial changes in hepatic portal glucagon concentration.