Glucagon satiety: diurnal variation after hepatic branch vagotomy or intraportal alloxan.

Hepatic vagotomized and hepatic portal alloxan-injected rats and their controls were tested for glucagon satiety at three time points during the circadian photoperiod: 6 hr into the light cycle with no food deprivation using a palatable liquid food; at the onset of the dark cycle after 6 hr food deprivation using pelleted rat chow; and 3 hr into the dark cycle after 9 hr food deprivation using pelleted chow. Glucagon failed to suppress intake in hepatic vagotomized and alloxan-treated rats when tests were conducted during the light cycle or at the onset of the dark cycle. In contrast, in tests conducted 3 hr into the dark cycle, glucagon suppressed food intake significantly in both hepatic vagotomized and alloxan-treated rats. Glucagon suppressed food intake significantly in controls in all tests. These results indicate that the hepatic vagus is not the sole mediator or glucagon satiety. Moreover, the fact that alloxan-treated rats and hepatic vagotomized rats responded in a similar manner to glucagon at all testing times suggests that hepatic portal alloxan treatment damages hepatic vagal fibers.