Hyperglycaemic effect of glucagon administered intracerebroventricularly in the rat

The intracerebroventricular (icv) administration of 100 ng glucagon resulted in more prolonged and pronounced elevations of plasma glucose levels than the intravenous injection of 100 ng glucagon. Insignificant changes in plasma IRI and IRG levels after icv glucagon administration contrasted to marked increases in both IRI and IRG levels after the iv injection. Icv glucagon-induced hyperglycaemia was completely prevented by the prior administration of atropine, phentolamine or hexamethonium, and partially inhibited by bilateral adrenalectomy, but not by propranolol pretreatment. These findings suggested that the hyperglycaemic effect is brought about through cholinergic and alpha-adrenergic neural pathways and partly via the adrenal medulla.