Medullary projections of rabbit carotid sinus nerve.

In New Zealand white rabbits, cholera-toxin HRP was injected into the carotid sinus nerve just proximal to the carotid sinus. After survival periods of 3-5 days the rabbits were anesthetized and the brain fixed with aldehyde solution. Transverse sections were cut on a sledge microtome and the sections reacted with the tetramethylbenzidine procedure. HRP-positive fibers entered the ipsilateral dorsolateral medulla at the level of the acoustic tubercle, joining the tractus solitarius. Positive fibres were found principally ipsilaterally in four regions of the medulla: in the caudal two thirds of the nucleus tractus solitarius, in its dorsolateral regions and, more caudally, in its commissural subdivision; in the dorsolateral aspect of the spinal nucleus of the trigeminal nerve; in the region ventral and ventrolateral to the tractus solitarius (extending beyond the nucleus tractus solitarius); and in the ventrolateral medulla oblongata.