Histochemical studies of noradrenergic innervation of the liver in untreated and daunomycin-pretreated guinea-pigs.

The pattern of noradrenergic innervation of guinea-pig hepatic tissue was examined by using the fluorescence method of Falk et al. (1962). The distribution of monoaminergic nerve fibers in untreated animals was clearly evident at the level of the portal vein, the hepatic artery and the bile duct. The hepatic artery was the most densely innervated. Mast cells and Kupffer cells had no connection with the adrenergic fibres. In daunomycin-pretreated animals, the hepatic cells appeared to be deep red in colour owing to the presence of the antibiotic. Some noradrenergic nervous fibres, never previously described, were unexpectedly distinguishable in the liver parenchyma against the background red colour of daunomycin-pretreated tissue. They appeared to be contiguous to the hepatocytes and were of different shapes: comma-like, V-like, or like a string of pearls. The nature and the functional role of these elements is briefly discussed.