Soma size comparison of the trigeminal ganglion cells giving rise to the ascending and descending tracts: a horseradish peroxidase study in the cat.

Soma size was compared between the trigeminal ganglion cells projecting to the main sensory trigeminal nucleus (Vs) and those projecting to the nucleus caudalis (Vc) of the spinal trigeminal nucleus in the cat after injection of horseradish peroxidase (HRP) into each nucleus. The results showed that the cells projecting to the Vc (Vc cells) contained by far a greater percentage of small cells than do those projecting to the Vs (Vs cells). In the Vc case, about one-half the total number of measured labeled cells were the smallest with a diameter less than 36 microns, whereas in the Vs cases, only a small proportion of the total number of measured labeled cells were that small. In addition, the results also made it clear that the Vs cells in the ophthalmic and maxillary divisions contained a higher percentage of larger cells than those in the mandibular division.