Adrenergic innervation of the oesophagus in the cat (Fellis domestica) and rhesus monkey (Macacus rhesus)

Summary The distribution of monoamines in the pharynx and oesophagus of the rhesus monkey (Macacus rhesus) and the cat (Felis domestica) was investigated by means of fluorescence microscopical and chemical methods. Fluorimetric determinations reveal the presence of varying amounts of noradrenaline in the pharynx and oesophagus of the rhesus monkey. The lowest amount (0.05 (g/g) was found in the lower part of the oesophagus, the so-called sphincter-segment. The middle and upper part of the oesophagus contain medium amounts of noradrenaline (0.06–0.09 g) whereas the highest concentration was detected in the pharynx (0.14 (g/g). Neither dopamine nor adrenaline occurred in the tissue pieces analyzed. Fluorescence microscopically noradrenaline was found to be located in varicose intramural nerve fibre plexus which innervate mucous glands and blood vessels in the pharynx of both species. In the rhesus monkey, the lamina muscularis mucosae of all parts of the oesophagus is supplied by a well developed noradrenergic ground-plexus. Preterminal and terminal varicose nerve fibres are distributed in myenteric and submucous ganglia of the oesophagus; the number of such ganglia decreases towards the lower segment. The density of the adrenergic innervation is higher in myenteric when compared to submucous ganglia. The arrangement of the intraganglionic terminals suggests that both axosomatic and axodendritic contacts occur in Auerbach's ganglia whereas axodendritic contacts seem to predominate in Meissner's ganglia. Myenteric ganglia situated close to the submucosa as well as true submucous ganglia may be occasionally seen to be traversed by faintly fluorescent non-varicosed fibres which do not establish any synaptic contacts. The fluorescence intensity of intraganglionic varicosities varies considerably; accordingly the transmitter content of individual varicosities seems to be very variable. The adrenergic innervation of the lamina muscularis is restricted to single contorted fibres being sparsely distributed throughout the longitudinal smooth muscle layer. The circularly arranged smooth musculature of the sphincter-segment lacks an adrenergic nerve supply. The vagus nerve carries sympathetic adrenergic fibres to the lower oesophagus and the cardia. Species differences between the innervation pattern in rhesus monkeys and cats are outlined: No adrenergically innervated ganglia occur in the submucosa of the cat. However, part of the myenteric ganglia in cats exhibit an adrenergic innervation pattern similar to that seen in submucous ganglia of the rhesus monkey. They might therefore be regarded as morphologically equivalent to the plexus submucosus which is, however, present in the whole gut. The density of the noradrenergic ground-plexus in the muscularis mucosae of the cat's oesophagus is less than that of the corresponding plexus in rhesus monkeys.The influence of noradrenaline upon the smooth musculature and the neurons from myenteric as well as submucous ganglia is discussed. From the point of view of the adrenergic innervation there is no structure corresponding to the sphincterlike lower oesophageal segment.Supported by the Deutsche Forschungsgemeinschaft and the Joachim-Jungius-Gesellschaft zur Förderung der Wissenschaften, Hamburg.