Crucial role of peripheral κ-opioid receptors in a model of periodontal disease in rats

• Published in: Journal of periodontal research 2008-12, Vol.43 (6), p.730-736
• Main Authors: Pacheco, C. M. F., Queiroz-Junior, C. M., Maltos, K. L. M., Caliari, M. V., Pacheco, D. F., Duarte, I. D. G., Francischi, J. N.
• Format: Article
• Language: English
• Subjects: 3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cyclohexyl)-benzeneacetamide, (trans)-Isomer - pharmacology; Analgesics, Opioid - pharmacology; Analgesics, Opioid - therapeutic use; animal model; Animals; Chronic Periodontitis - drug therapy; Chronic Periodontitis - physiopathology; Dentistry; Disease Models, Animal; inflammation; Male; Morphine - pharmacology; Morphine - therapeutic use; Naltrexone - analogs & derivatives; Naltrexone - pharmacology; Narcotic Antagonists - pharmacology; opioid; periodontal disease; Peripheral Nervous System - physiology; Rats; Rats, Sprague-Dawley; Receptors, Opioid, delta - physiology; Receptors, Opioid, kappa - agonists; Receptors, Opioid, kappa - antagonists & inhibitors; Receptors, Opioid, kappa - physiology
• ISSN: 0022-3484; 1600-0765
• DOI: 10.1111/j.1600-0765.2008.01102.x

Background and Objective:  Periodontal disease is a chronic inflammatory condition of the tooth supporting tissues, the periodontium. Opioids have been shown to account for the relief of various chronic and acute inflammatory conditions. The aim of the present study was to investigate the participation of peripheral opioid receptors in development of periodontal disease. Material and Methods:  Morphine and selective agonists and antagonists of opioid receptors were used in an experimental model of ligature‐induced periodontal disease in rats. To evaluate the development of disease, the loss of fiber attachment, alveolar bone and number of cells in periodontal tissues were assessed. Measurements of these indicators were obtained by morphometric analysis of histological sections of periodontal‐diseased tissues stained with hematoxylin and eosin. Results:  Local administration of either morphine or a selective κ‐opioid agonist for three consecutive days from the onset of periodontal disease reduced the loss of periodontal tissues, without changing the number of leukocytes in inflamed periodontium. Nor‐binaltorphimine, a selective κ‐antagonist, reversed the beneficial effects of both morphine and the compound U‐50,488 in this model. The use of either an agonist or an antagonist of δ‐opioid receptors, however, did not affect disease progression. Conclusion:  Our results showed that the beneficial effect of opioids in periodontal disease depended mainly on the activation of specific κ‐opioid receptors located in the periphery. Activation of such receptors could be considered in the management of periodontal disease, since it would not present the classical central side‐effects associated with opioid use.