Adrenergic nerves and receptors in the liver.

The finding of an adrenergic innervation of the liver parenchyma in many mammalian species, using the Falck-Hillarp fluorescence method, together with the electron microscopy documentation of synaptoid contacts between adrenergic nerve terminals and hepatocytes, constitute an important morphological basis for the possibility of a direct role of the sympathetic nervous system on the liver function. The results from the morphological studies are in accordance with physiological experiments, carried out in many laboratories, showing that direct electrical stimulation of the hepatic nerves in vivo leads to an increased release of glucose from the hepatocytes. These findings have augmented the demand for detailed studies of the receptor systems mediating the effects of catecholamines on liver metabolism. Our pharmacological studies on liver tissue in vitro have revealed a predominant role for adrenergic betareceptors mediating glucose output in man.