Topographic distribution of laryngeal motor neurons in the nucleus ambiguus of the guinea pig studied by horseradish peroxidase (HRP) technique.

The topographic distribution of Nucleus Ambiguus (NA) motor neurons innervating the intrinsic laryngeal musculature in the guinea pig has not been studied previously. We used 25 guinea pigs anaesthetized by Penthrane (Methoxyflurane) inhalation. Horseradish peroxidase type VI (40%) was used. The motor neurons traced are distributed in cellular groups elongated rostro-caudally in a tract of the brain stem situated between a rostral plane compatible with the location of the retrofacial nucleus, and a caudal plane some millimetres below the obex. The motor neurons observed do not exhibit differential morphology in relation to the different muscles studied.