On the sympathetic innervation to the cat's liver and its role for hepatic glucose release

Morphology and function of the adrenergic innervation of the liver were studied in cats. Fluorescence microscopy revealed a dense network of adrenergic nerve fibres in association with interlobular vessels and a sparse, but unequivocal innervation of the hepatocytes. These parenchymal adrenergic nerve fibres were more frequent in kittens (2 months old) than in adult cats. Electrical stimulation of the hepatic sympathetic nerves in the adult adrenalectomized cat evoked a small but insignificant increment (1-2 mM) of arterial plasma glucose concentration. When both hepatic and pancreatic sympathetic nerves were stimulated simultaneously, arterial plasma glucose concentration increased significantly by about 6 mM. We conclude that the pronounced hyperglycemic effect of activation of the sympathetic nervous system in the cat is mediated mainly via an adrenergic influence on the release of insulin and glucagon from the pancreas. The sympathetic innervation of the cat liver parenchyma seems to contribute to the hyperglycemia to a minor extent only.