A horseradish peroxidase study of vagal motoneurones with axons in cardiac and pulmonary branches of the cat and dog.

The location, within the brain stem, of vagal efferent neurones with axons in the cardiac and pulmonary branches of the cat, and the cardiac branch of the dog, have been defined. Horseradish peroxidase was applied to the cut central ends of these vagal branches and, after an appropriate time, sections of the brain stem were examined for labelled cell bodies. Labelled cell bodies were found ipsilaterally in the dorsal motor vagal nucleus, the nucleus ambiguus and in the reticular formation between these two nuclei. We suggest that the dual location for cell bodies of vagal axons may represent a separation of somata with myelinated and non-myelinated vagal axons to the nucleus ambiguus and the dorsal motor vagal nucleus respectively.