The potential of cervical primary afferents to sprout in the spinal nucleus of V following long term trigeminal denervation

Abstract

Because of the intimate structural and functional relationships between cervical and trigeminal primary afferents in the caudalmost portion of the subnucleus caudalis of the trigeminal nerve, the possibility that cervical afferents might sprout to occupy vacated synaptic sites when the trigeminal afferents degenerated was investigated. Four adult cats were kept for periods of 11.5–24 months after trigeminal rhizotomy at which time symmetrical upper cervical spinal ganglionectomies were done. The ensuing degeneration was studied by the Nauta-Gygax and Fink-Heimer I methods at 6–13 days postoperatively. No evidence could be found that sprouting of cervical primary afferents had occurred at any level on the chronically denervated side. The significance of these findings is discussed in the light of past and recent observations on the problem of plasticity of connections in the mammalian central nervous system.