Neuropeptide expression in the ferret trigeminal ganglion following ligation of the inferior alveolar nerve

Previous studies have found changes in neuropeptide expression in trigemina l ganglion cells after inferior alveolar nerve (IAN) section. These changes may play a part in the persistent sensory abnormalities that can be experi enced after trigeminal nerve injuries. Here, neuropeptide expression after IAN ligation was studied, as this type of injury is thought to be more like ly to result in sensory disturbances. The neuropeptides investigated were s ubstance P, calcitonin gene-related peptide, enkephalin (ENK), galanin (GAL ), neuropeptide Y (NPY) and vasoactive intestinal polypeptide. In anaesthet ised adult female ferrets the left IAN was sectioned and the central stump tightly ligated. Recovery was allowed for 3 days, 3 or 12 weeks before perf usion-fixation. In a second procedure, 1 week before perfusion, the IAN was exposed and an injection made central to the injury site, using a mixture of 4% Fluorogold and 4% Isolectin B4 conjugated to horseradish peroxidase, to identify cell bodies with axons in the inferior alveolar nerve and cells with unmyelinated axons within this population, respectively. Control expe riments involved tracer injection alone. After harvesting the tissue, sagit tal sections were taken from both the right and left ganglia and immunohist ochemical staining used to reveal the presence of peptides and Isolectin B4 tracer. The results showed a significant decrease in GAL expression after injury and an increase in ENK and NPY expression. No significant difference s were seen in the expression of the other peptides or in the proportion of lectin-positive cells at any time after injury. When compared with previou s data, significant differences were found between peptide expression follo wing nerve ligation and nerve section. These results reveal that the change s in neuropeptide expression in the trigeminal ganglion that follow IAN inj ury are dependent upon the type of injury. The extent to which changes in t he central neuropeptide levels contribute to the development of sensory dis orders remains to be established. (C) 2001 Elsevier Science Ltd. All rights reserved.