Choline acetyltransferase and calcitonin gene-related peptide immunoreactivity in motoneurons after different types of nerve injury

Abstract

This study examined changes in choline acetyltransferase and calcitonin gene-related peptide immunoreactivity in hypoglossal motoneurons of rats at 1, 3, 7, 20 and 50 days after three types of nerve injury: crush, transection and resection. Peripheral reinnervation was assayed by retrograde labelling of the motoneurons after injections of the exogenous protein, horseradish peroxidase, into the tongue. Maximal reduction in choline acetyltransferase immunostaining occurred at seven days after nerve damage and the amount of the decrease was related to the nature of the injury. The recovery of choline acetyltransferase to normal levels was related to the timing of reinnervation after nerve crush, but not after transection or resection injuries. In contrast to these findings, a rapid increase in calcitonin gene-related peptide immunoreactivity preceded the decrease in choline acetyltransferase levels. A striking increase in calcitonin gene-related peptide immunoreactivity was observed at one day postoperative and was maximal at three days postoperatively for all injuries. Later changes in calcitonin gene-related peptide levels were dependent on the type injury. Increased calcitonin gene-related peptide staining persisted to 20 days after nerve crush. After nerve transection or resection, calcitonin gene-related peptide immunoreactivity decreased to basal levels at seven days postoperatively. This declination was followed by a second rise in calcitonin gene-related peptide immunolabeling at 20 days for nerve transection or 50 days after resection. Nearly complete reinnervation was established by 20 days after nerve crush. At 50 days after transection, less than half the number of normally-labelled neurons contained horseradish peroxidase. At this time only 1% of those whose axons had been resected were labelled. These observations suggest that different mechanisms regulate the responses of choline acetyltransferase and calcitonin gene-related peptide to nerve injury. The present results indicate that choline acetyltransferase levels in motoneurons can not be used to predict either the likelihood of or the timing of reinnervation after nerve transection or resection. However, our results strengthen the premise that an increased of calcitonin gene-related peptide immunoreactivity serves as a reliable index for predicting nerve regeneration/reinnervation after cranial nerve injury.

BDNF and NT-4/5 exert neurotrophic influences on injured adult spinal motor neurons

“…Nerve crush results in greater acute elevations in the levels of p75'@ mRNA reexpression as compared to nerve transection for both facial and hypoglossal motor neurons (Saika et al, 1991;Hayes et al, 1992). Furthermore, as compared to nerve transection, nerve crush results in smaller reductions in ChAT immunostaining in adult cranial motor neurons (Armstrong et al, 1991;Borke et al, 1993). The present study extends these findings to the RDLN spinal motor neurons where nerve crush injury both augments p75rn@ immunostaining and also reduces the loss in ChAT immunostaining relative to losses observed after nerve cut.…”

Alterations in the Local Axonal Environment Influence Target Reinnervation and Neuronal Survival After PostnataI Axotomy

“…The incidence of apoptosis appeared to be greatest in the 10 DPN rats at 2 DPO after nerve transection. This finding is in agreement with previous studies of HRP labeling in hypoglossal iluclei (Blake-Bruzzini et aI., 1997;Borke et al, 1993;Hall and Borke, 1988). Unlabeled neurons in the nuclei of uninjured hypoglossal nerves following HRP injections represent a distinct interneuron population that does not project to the tongue musculature (Boone and AIdes, 1984).…”

Differential regulation of the expression of neurotrophin receptors in rat extraocular motoneurons after lesion

“…In motoneurons, a reduction in choline acetyltransferase (ChAT) expression, an enzyme involved in the synthesis of the neurotransmitter acetylcholine, often occurs after nerve damage (Lams et al, 1988;Matsuura et al, 1997;Wang et al, 1997). In contrast, other molecules like calcitonin gene-related peptide (CGRP), a protein related to rearrangement of synaptic connections, increase their expression after lesion (Calderó et al, 1992;Borke et al, 1993;Piehl et al, 1993;Fukuoka et al, 1999).…”