Pancreatic glucagon, food deprivation and feeding in intact and vagotomized rabbits.

Thirty New-Zealand female rabbits were implanted with hepatic-portal cannulas and six simultaneously underwent bilateral subdiaphragmatic vagotomy. When recovered, all animals received pancreatic glucagon infused at 1.0 cc/min for a total dosage of 12 microgram in 3.0 cc of isotonic saline. On alternate days, isotonic saline alone was infused as a control. Twelve intact and six vagotomized animals received infusions terminating food deprivations of 4, 8, and 24 hr while the remaining animals received the infusions only when free feeding. The feeding behavior of all animals was measured at 0.5, 1 and 2 hr postinfusion. Glucagon significantly suppressed feeding relative to saline only in 0- and 4-hr-food-deprived intact rabbits. Longer deprivations followed by glucagon did not produce suppression, and glucagon was completely ineffective in suppressing feeding in vagotomized animals. Although glucagon infusion in 4-hr food-deprived intact rabbits produced 38% suppression of food intake during the first hr postadministration, glycogen analysis revealed no significant reduction under the behavioral testing paradigm. These results indicate that glucagon can suppress food intake without depletion of liver glycogen. It is suggested that glucagon is not a satiety signal but can probably suppress feeding through initiating glycogenolysis.