Projections of extraocular muscle primary afferent neurons to the trigeminal sensory complex in the cat as studied with the transganglionic transport of horseradish peroxidase.

The central projections of extraocular muscle primary afferent neurons were examined in the cat by means of transganglionic axonal transport of wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP). Injections of the extraocular muscle with WGA-HRP resulted in transganglionic terminal labeling within the ipsilateral trigeminal sensory complex. Although the density of trigeminal projections varied among cases, labeled axons and terminals were heavily and consistently found within the rostroventral portion of the pars oralis of the spinal trigeminal nucleus. The caudal part of the trigeminal principal sensory nucleus occasionally contained moderate labeling but very few deposits of HRP reaction product were noted in the pars interporalis and pars caudalis of the spinal trigeminal nucleus.