Evidence for the site of the superior salivatory nucleus in the guinea pig: a retrograde HRP study.

Horseradish peroxidase (HRP) was applied to the proximal end of the severed lingual nerve distal to where it was joined by the chorda tympani nerve in 15 female guinea pigs. Labeled cells were seen in the lateral reticular formation dorsal to the facial nucleus along the medial edge of the spinal nucleus of V. These cells were aligned vertically and partially within the facial nerve fibers which were emerging from the facial nucleus lying ventrally. HRP-reactive axons were also seen among the facial nerve fibers coursing dorsomedially toward the genu of the facial nerve. These results demonstrated for the first time the locus of the superior salivatory nucleus in the guinea pig and were consistent with anatomical results previously reported in other species. In addition, labeled fibers indicated that superior salivatory nucleus axons became incorporated in the facial nerve immediately dorsal to its origin.