Further observations on transganglionic degeneration in trigeminal primary sensory neurons.

Transganglionic degeneration has been studied with the Fink-Heimer method in the trigeminal sensory nuclei of adult cats and rats following peripheral nerve transections. Degeneration was observed ipsilaterally as well as contralaterally in all cats, surviving 11-30 days after transection of the infraorbital nerve. In the rats the infraorbital or the auriculotemporal nerve was transected. After transection of the former nerve the first signs of transganglionic degeneration were observed after 7 days postoperative survival and even after 130 days there were still a lot of degenerating structures present. Between 7 and 14 days survival there was a small amount of degeneration in substantia gelatinosa. After transection of the auriculotemporal nerve, degeneration was observed only in the most caudal parts of the trigeminal sensory nuclear complex. Opposite to the situation in the cat, there was no contralateral degeneration in the rat. All degeneration areas were somatotopically organized, both in the cat and in the rat. The results are discussed in relation to a previous study of transganglionic degeneration in the trigeminal sensory nuclear complex by the authors and to anatomical and physiological studies of somatotopic organization in the trigeminal sensory nuclei. They clearly show the value of transganglionic degeneration used as a tool for analysis of central projections of primary sensory neurons.