Location in the nodose ganglion of the perikarya of neurons whose axons distribute in the epithelium of the rat trachea.

The numbers of axons/unit length and of axons/group in the epithelium of the right and left sides of the trachea were determined in longitudinally orientated sections of specimens taken from five control rats, and from groups of five or six rats three days after section of the left vagus nerve above or below the nodose ganglion or section of the superior laryngeal and pharyngeal branches of the left vagus. After section of the vagus nerve below the nodose ganglion, there was a highly significant reduction in the number of axons/unit length in the epithelium of the ipsilateral side of the trachea, a significant reduction in the number of axons/group on this side and a small reduction in the number of axons/unit length on the contralateral side. The absence of similar changes in specimens from rats in which the vagus nerve was sectioned above the nodose ganglion, and in rats in which the branches from the ganglion were sectioned, indicated that the intraepithelial axons are derived from neurons whose perikarya are located in the ganglion and is consistent with the view that the axons are afferent. In addition to axons with terminals which resembled those which, in other tissues, have been defined as pain afferents, occasional axons with terminals containing numerous small clear vesicles were identified in the epithelium. The absence of these axons from the epithelium only in specimens taken from the ipsilateral side of the trachea after infranodose section of the left vagus nerve suggests that these may also be afferent.