Efferent connections of the vestibular nuclei in the rat: a neuromorphological study using PHA-L.

The efferent connections of the superior, medial, lateral, and descending vestibular nuclei were studied with anterograde tracing methods in rats. The following areas of termination could be discerned: (1) In the diencephalon, labeled terminals were detected in the thalamus. (2) In the mesencephalon, the red nucleus and motor nuclei involved in eye movements were richly supplied by the vestibular nuclei. (3) In the rhombencephalon, extensive intrinsic connections of all vestibular nuclei were demonstrated. Strong commissural connections were found among the medial, superior, and descending vestibular nuclei. The inferior olive received labeled fibers exclusively from the lateral vestibular nuclei. Individual differences were demonstrated in the termination areas in the reticular formation. (4) In the spinal cord, most of the descending vestibular fibers were found in the ipsilateral anterior funiculus.