Evidence that blood vessels in guinea-pig lung are supplied by both noradrenergic and dopaminergic axons.

Assay of catecholamines in guinea-pig lung showed that the amount of dopamine in this tissue is 3-4 times greater than that predicted to be associated only with noradrenergic nerves, and is depleted by animal treatment with 6-hydroxydopamine. Fluorescence microscopy after formaldehyde condensation did not reveal any non-neuronal stores of catecholamines within the lung. The pulmonary and bronchial arterial vessels are accompanied by numerous fine nerve fibres that exhibit immunoreactivity for tyrosine hydroxylase, and are therefore presumed to be catecholaminergic. A small proportion of these fibres are also immunoreactive for DOPA decarboxylase. The results are consistent with innervation of pulmonary and bronchial resistance vessels by dopaminergic as well as noradrenergic sympathetic axons.