The reaction of mesencephalic trigeminal neurons to peripheral nerve transection in the adult rat

Abstract

The effects of peripheral nerve transection on mesencephalic trigeminal (MeV) neurons have been studied qualitatively and quantitatively in the rat. In the qualitative part of the study the brain stem was studied in Fink-Heimer stained sections 3-30 days after a masseteric nerve transection. Degeneration argyrophilia was observed both in the MeV tract and in the supratrigeminal and trigeminal motor nuclei, as well as in the lateral part of the brain stem reticular formation. The first signs of transganglionic degeneration (TGD) were seen 7 days postoperatively, and the amount of degeneration increased considerably with longer survival times. A quantitative analysis of the MeV nucleus was made 60 days after transection of the left masseteric nerve. This analysis showed a 10.5-22.7% reduction of cells on the side that had undergone masseteric nerve transection. The mean difference (left vs right side) was -2.4% in animals that had not been operated on. These findings show that mesencephalic trigeminal neurons with proprioceptive functions are very sensitive to peripheral nerve injury with a substantial cell loss and TGD as the result.

Neurodegeneration of Trigeminal Mesencephalic Neurons by the Tooth Loss Triggers the Progression of Alzheimer’s Disease in 3×Tg-AD Model Mice

“…The presence of ATF3 immunoreactivity in Vmes neurons was considered to be the result of damage responses due to the extraction of maxillary molars. Indeed, damage to Vmes neurons by peripheral nerve transection has been reported [ 6 ]. The results of the present study revealed cell death in Aβ 42 -IR Vmes neurons 2 weeks after tooth extraction.…”

“…Based on this notion, it is highly possible that neurodegeneration in Vmes can spread to the LC. Previous studies have shown that the nerve endings of Vmes neurons are distributed in the periodontal ligament as well as muscle spindles of the masticatory muscles [5], and that the degeneration of Vmes neurons leading to neuronal loss in the Vmes occurs after peripheral axotomy [6] and tooth extraction [7].…”

Nitric oxide synthase/nicotinamide adenine dinucleotide phosphate‐diaphorase in the brainstem trigeminal nuclei after transection of the masseteric nerve in rats

“…Thus, transection of the masseteric nerve might be the direct cause of NADPH‐d and/or nNOS induction in the Vmes neurons. Vmes neurons are very sensitive to peripheral nerve injury with a substantial cell loss (Raappana and Arvidsson, 1992). This would be in line with the idea that persistently increased levels of nNOS in neurons may be involved in slowly progressive nerve cell death following nerve transection, in that it may lead to an increased vulnerability of the neurons to calcium‐mediated neurotoxicity (Bredt and Snyder, 1989; Dawson et al, 1991).…”

Experimental Trigeminal Nerve Injury

“…Many afferents in the masseteric nerve have their cell bodies in the mesencephalic nucleus. Transection of this nerve results in death of from 10.5 to 22.7% of the cells in the mesencephalic nucleus (Raappana and Arvidsson, 1992). This differs from simple transection of the inferior alveolar nerve, which does not result in ganglion cell death (Holland and Robinson, 1990b).…”

“…This differs from simple transection of the inferior alveolar nerve, which does not result in ganglion cell death (Holland and Robinson, 1990b). It may be that, as Raappana and Arvidsson (1992) suggest, proprioceptive neurons are very sensitive to injury, or it may be the result of the greater separation, due to retraction, of the cut ends after masseteric nerve transection. It is also possible that the micro-environment of these neurons within the central nervous system rather than in a peripheral nervous system ganglion may affect their susceptibility.…”