Retrograde labelling in vivo of vagus nerve nucleus in rat by carbocyanine dye.

To elucidate the patterns of visceral innervation of the vagus nerve in rats, we labelled the severed efferent path at the level of the neck in vivo by applying a solution of 0.1% carbocyanine dye DiI/100% ethanol. Two weeks after dye application, horizontal sections of the brain stem were analysed quantitatively under an epifluorescence microscope. Particles of DiI were present in neuronal cell bodies and the cellular processes in the dorsal motor nucleus (DmoX) of the vagal nerve and nucleus ambiguus (Nam). Approximately 80% of DiI-labelled cells were located in the DmoX whereas 16% were in the Nam. The rest of the labelled cells were in the vicinity of the central canal. The DiI labelling technique appears to be a useful new technique for quantitative analysis of central neurones sending visceral efferents.