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Lack of adrenergic nerves in the circular smooth muscles of ductus arteriosus persistens.

Persistent ductus arteriosus obtained from children at operation were studied by means of a fluorescence microscopical technique, specific for catecholamine containing structures. Adrenergic nerves were found in the peripheral parts of the vessel but were lacking or very sparse in the medial, circular musculature. In this respect the persistent ductus arteriosus differs from the normal ductus, where the medial muscle layer is richly supplied with adrenergic nerves. The results further indicate the necessity of an adrenergic mechanism for the normal closure of the vessel and constitute a new aetiological explanation for the persistence of ductus arteriosus.