Axonal projections to the ventrolateral nucleus of the solitary tract revealed by double labelling of retrograde fluorescent markers in the cat.

The retrofacial nucleus project bilaterally to the ventrolateral nucleus of the tractus solitarius (vlNTS) as revealed by means of retrograde transport of the fluorescent markers, Fast blue (FB) and Diamidino yellow (DY), in the cat. Some of the neurons of the retrofacial nucleus send axonal ramifications to both vlNTS. Extensive projections from other brainstem respiratory related nuclei to the vlNTS were also observed: bilaterally from the nucleus ambiguus, nucleus retroambiguus and nucleus parabrachialis medialis, and ipsilaterally from the Kölliker-Fuse nucleus. Axonal projections from the contralateral vlNTS were also observed.