Redundant vagal mediation of the synergistic satiety effect of pancreatic glucagon and cholecystokinin in sham feeding rats

Abstract

Simultaneous intraperitoneal injection of pancreatic glucagon (PG) and cholecystokinin (CCK) results in a functionally synergistic satiety effect in non-deprived sham feeding rats ("PG-CCK satiety"). That is, PG and CCK together inhibit feeding significantly more than the sum of their individual effects. Because the individual satiety effect of each peptide on normal feeding is dependent on the abdominal vagus nerve, we tested the vagal mediation of this synergistic effect of PG plus CCK. Vagotomies were verified anatomically and, in one experiment, histologically. Total abdominal vagotomy blocked PG-CCK satiety. Neither selective vagotomies of the hepatic, the gastric, the celiac, the gastric and celiac, nor the gastric and hepatic branches, however, affected PG-CCK satiety. This indicates that the vagal contribution to the synergistic satiety effect of PG plus CCK on sham feeding is redundant. Although some vagal fibers are necessary for PG-CCK satiety, no individual branch is required for the effect, and at least two branches, the hepatic and celiac, are each sufficient for mediating it.