neuropeptide-y and Sensation-Disorders

Previous studies have found changes in neuropeptide expression in trigeminal ganglion cells after inferior alveolar nerve (IAN) section. These changes may play a part in the persistent sensory abnormalities that can be experienced after trigeminal nerve injuries. Here, neuropeptide expression after IAN ligation was studied, as this type of injury is thought to be more likely to result in sensory disturbances. The neuropeptides investigated were substance P, calcitonin gene-related peptide, enkephalin (ENK), galanin (GAL), neuropeptide Y (NPY) and vasoactive intestinal polypeptide. In anaesthetised 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 perfusion-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 experiments involved tracer injection alone. After harvesting the tissue, sagittal sections were taken from both the right and left ganglia and immunohistochemical 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 differences 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 previous data, significant differences were found between peptide expression following nerve ligation and nerve section. These results reveal that the changes in neuropeptide expression in the trigeminal ganglion that follow IAN injury are dependent upon the type of injury. The extent to which changes in the central neuropeptide levels contribute to the development of sensory disorders remains to be established.

Topics: Analysis of Variance; Animals; Axons; Calcitonin Gene-Related Peptide; Cell Count; Disease Models, Animal; Enkephalins; Female; Ferrets; Fluorescent Dyes; Follow-Up Studies; Galanin; Gene Expression; Horseradish Peroxidase; Immunohistochemistry; Lectins; Ligation; Mandibular Nerve; Neural Pathways; Neuropeptide Y; Neuropeptides; Sensation Disorders; Statistics as Topic; Stilbamidines; Substance P; Trigeminal Ganglion; Trigeminal Nerve Injuries; Vasoactive Intestinal Peptide

Neuropeptide Y (NPY) is widely distributed throughout sympathetic nerve endings where it is co-stored and co-secreted with noradrenaline. It is considered a marker of noradrenergic function. To determine the role of NPY in the pathogenesis of juvenile headache, we determined its plasma levels in two groups of young migraine patients (with and without aura), in a group of episodic tension-type headache patients and in a group of age and sex-matched healthy subjects. Significantly lower plasma levels of NPY were evident in the migraine patients with aura (P < 0.001) and, to a lesser extent, in the migraine patients without aura (P < 0.02), both assessed in the interictal period, with respect to the control group. Plasma NPY levels tended to significantly increase during attacks in migraine patients with aura (P < 0.0009). A less evident, though significant increase was also present during attacks in migraine patients without aura (P < 0.02). No significant variations were observed between headache-free periods and attacks in tension-type headache patients. Reduced NPY levels in the interictal period can be considered further evidence of the derangement of the sympathetic function in the course of migraine, particularly that with aura. The increase in NPY levels during migraine attacks could be an expression of sympathetic activation, even though the functional status of this system is less efficient.

Topics: Adolescent; Child; Female; Headache; Humans; Male; Migraine Disorders; Muscle Contraction; Neuropeptide Y; Sensation Disorders