Effects of Dexamethasone on Salivary Hypofunction Following Acute Duct Ligation

In previous studies, ligation of the main excretory duct of the rat submandibular gland for 24 hours caused sialadenitis and reduced salivary secretion from the de-ligated gland (Carpenter et al. 2003, J. Dent. Res. Vol 82:B-397). Objective: to examine the effects of the anti-inflammatory steroid dexamethasone on salivary gland hypofunction in the ligated rat submandibular (SM) gland model. Methods: all experiments were conducted under licence and with appropriate local ethical committee approval. The right SM glands of 5 Male Han-Wistar rats (body wt. 225-250g) were ligated under recovery anaesthesia using a metal microclip from an intraoral approach avoiding the chorda lingual nerve. Dexamethasone (5.45mg/Kg I.M) was administered during recovery from anaesthesia. Twenty four hours later, under non-recovery anaesthesia, the right SM duct was cannulated on the gland side of the ligature. The left gland was also cannulated. Secretion was stimulated by infusion of autonomimetics into the femoral vein. Salivas and salivary glands were collected, weighed and analysed. Results: Mean right SM gland weight was similar to contralateral control gland weight (R vs L, 0.18±0.03g vs 0.20±0.02g, n=5) and microscopy of haematoxylin and eosin stained sections revealed little evidence of inflammatory cell infiltration of ligated glands. Salivary flow rate evoked by methacholine (12µg.min-1.kg-1) was decreased (p<0.05, by paired Students t test) by approximately 50% (99±14µl.min-1.g-1) compared to the left SM (204±19µl.min-1.g-1). Salivary protein output was similarly reduced. Conclusion: salivary gland hypofunction as a result of short-term duct ligation cannot be attributed solely to sialadenitis. Acknowledgement: this work was supported by the Wellcome Trust.