The effect of D-glucose on the firing rate of glucose-sensitive vagal afferents in the liver in comparison with the effect of 2-deoxy-D-glucose.

Afferent discharges were recorded from nerve filaments dissected from the hepatic branch of the vagus nerve in the guinea-pig in experiments on isolated and perfused liver preparations and on those done in vivo. A significant decrease in discharge rate was observed following injection of D-glucose into the portal vein but not after similar injections of D-mannose, D-fructose, D-galactose, L-glucose, D-xylose or D-arabinose. The mean discharge rate of these fibers was inversely related to the concentration of glucose in the portal vein. The administration of a glucose analogue, 2-deoxy-D-glucose (2-DG), caused an increase in discharge rate. The results suggest that the inhibitory effect of D-glucose on the rate of firing and facilitatory effect of 2-DG on firing are related to the facilitation or inhibition of glucose metabolism in the glucose sensors in the liver.