Effect of centrally administered glucagon on liver glycogen & enzymes in anaesthetised dogs

Glucagon (0.01 microgram) administered through the intracerebroventricular route in anaesthetised mongrel dogs, caused a significant rise in blood glucose and a fall in liver glycogen (P less than 0.01). Concurrently, it increased the liver phosphorylase, glutamic oxaloacetic transaminase, glutamic pyruvic transminase and lipase activities by 30 min. Identical changes were observed in vagotomised animals. In pancreatectomised animals as well as in spinal cord transectomised animals, glucagon did not cause these changes. The study indicated that the hyperglycaemia produced by the centrally administered glucagon, is possibly a result of liver glycogenolysis and gluconeogenesis induced by endogenous glucagon secreted from the pancreas, the stimulus for which is the hypothalamo-pancreatic fibres responding to glucagon sensitive neurones in the hypothalamus.