Extrinsic adrenergic innervation of the extrahepatic biliary duct system in guinea-pigs,cats and rhesus monkeys

Summary The localization of catecholamines has been investigated in the extrahepatic biliary duct system of cats, guinea-pigs and rhesus monkeys. In fluorimetric determinations noradrenaline was found to be the main primary catecholamine present in the biliary tract of rhesus monkeys. There exist regional differences in the noradrenaline content: Fairly low amounts were detected in the lower fundus of the gall-bladder (0.28 g/g). Increasing concentrations were measured in the corpus vesicae felleae (0.35 g/g), reaching a maximum level in the collum vesicae (0.49 g/g) and the ductus cysticus (0.50 g/g). The noradrenaline content of the choledochus and the choledocho-duodenal junction including Oddi's sphincter was much lower: 0,27 and 0,25 g/g respectively. The noradrenaline level in the small intestine of the rhesus monkey amounted to less than half the concentration found in the biliary ducts. Neither dopamine nor adrenaline have been detected. Fluorescence microscopical analysis reveals the presence of adrenergic nerves in the bile ducts which correspond to the measured noradrenaline concentrations: All parts of the biliary duct system in the different species investigated contain an elaborate perivascular adventitial plexus and adrenergic fibres confined to adventitial non-adrenergic ganglia. In guinea-pigs adrenergically innervated ganglia extend into the smooth muscle layer. The smooth muscle layer of the gall-bladder and the terminal choledochus in cats and rhesus monkeys is penetrated by a wide-meshed adrenergic ground plexus. This plexus was absent in guinea-pigs. The smooth musculature of the sphincter Oddi lacks a specialized adrenergic nerve supply in all species investigated. Finally, bound to the arterial vascular bed inside the propria in all parts of the biliary tract from all species investigated a prominent perivascular plexus is present. It is concluded that the smooth musculature of the gall-bladder and the terminal choledochus (the sphincter region excluded) in cats and monkeys receives 1. a direct sympathetic noradrenergic inhibitory innervation and 2. an indirect sympathetic noradrenergic inhibitory innervation which acts on intrinsic excitatory neurons and is present in all species investigated. The functional significance of the direct and indirect inhibitory innervation to the smooth musculature of the gall-bladder is discussed in detail.Dedicated to Professor Bengt Falck.Supported by the Deutsche Forschungsgemeinschaft and Joachim-Jungius-Gesellschaft zur Förderung der Wissenschaften, Hamburg.