EFFECTS OF STREPTOZOTOCIN-INDUCED DIABETES ON NEUROGENIC INFLAMMATIONOF GINGIVOMUCOSAL TISSUE IN RAT

It has been suggested that the unmyelinated small diameter afferent no ciceptive C-fibres are impaired in diabetes mellitus. We have recently demonstrated that these fibres are the prerequisite for neurogenic in flammation induced by mechanical or chemical irritations. These experi ments were designed to characterize the neurogenic inflammatory respon ses of gingivomucosal tissue in the early phase of experimental induce d diabetes mellitus in rat. Effect of dental ligature on the gingivomu cosal (GM) vascular permeability was studied in control rats and in ra ts pretreated with streptozotocin at d 7 and 14 following streptozotoc in administration. In separate groups of control and streptozotocin di abetic rats studies were also performed to investigate the effect of l ocal capsaicin application on GM vascular permeability on d 14. Vascul ar permeability was assessed by means of Evans blue extravasation. The ligature placed around the mandibular left first molar caused a signi ficant increase vascular permeability of GM tissue on the ipsilateral side on both d 7 and 14 after the ligation in control rats. In strepto zotocin diabetic rats on d 7, there was also a significant elevation o f Evans blue extravasation in the tissue tested on the ligature side. However, on d 14 the ligation failed to produce any changes in Evans b lue extravasation on the ipsilateral side, i.e. no difference in GM va scular permeability could be recorded between the two sides in strepto zotocin diabetic rats. Topical capsaicin administration produced signi ficant Evans blue extravasation in GM tissue of control rats compared to that observed in diabetic rats on d 14 after streptozotocin treatme nt. Electron microscopic and light microscopic studies demonstrated fi bre degeneration of the C neurones and less inflammatory cells in stre ptozotocin-induced diabetes in the gingivomucosal tissue. These findin gs appear to indicate that the inflammatory responses induced by mecha nical (dental ligature) and/or chemical irritants (topical application of capsaicin) in the gingivomucosal tissue are altered in streptozoto cin diabetic rats and this alteration is due to the diabetes-induced d amage to the unmyelinated C fibres.