A role for the liver in the effects of glucagon on food intake in domestic fowl.

ABSTRACT

Adolescent cockerels of an egg-laying strain were prepared with catheters into the hepatic portal vein (HPV) and offered a standard poultry ration ad lib. Injection of 10, 100 and 1000 micrograms of bovine glucagon into the HPV caused a depression in intake which was significantly different from the control from 60 to 90 minutes after injection and was related to the logarithm of the dose. In birds prepared with HPV and jugular vein catheters, 1000 micrograms of glucagon had a similar depressing effect on intake irrespective of route of administration. In cockerels vagotomised at the level of the proventriculus, doses of glucagon up to 1000 micrograms injected into the HPV had no significant effect on intake. When vagotomised and sham-operated birds, in direct comparison, were injected with 0, 5 and 50 micrograms glucagon, there was s significant depression with both doses in the sham-operated cockerels but no effect in those which were vagotomised. However, the vagotomised birds had low control food intakes and the data obtained from them must be interpreted with caution. The conclusion is drawn that glucagon affects liver metabolism to influence the information transmitted via the vagus nerves to the central nervous system circuits involved in the control of feeding.