Novel experimental model of non-infectious pharyngitis in rats

Currently, there is a paucity of scientific literature and reports related to screening models for non-infectious type of pharyngitis. In this context, we made a sincere attempt to establish a novel animal model for screening drugs against non-infectious pharyngitis in rats. We have considered the use of pyridine, croton oil and their combination for inducing non-infectious pharyngitis in rats.Various concentrations of pyridine were applied topically to the pharyngeal region of rats and the extent of inflammation was assessed by Evans Blue (EB) dye exudation test, evaluating the serum levels of proinflammatory cytokines and histopathology. Dexamethasone and diclofenac were used as reference standards.Upon pyridine application (2.5%, 5%, 10%, 20%, 40% and 80% in saline), dose-dependent increase in EB dye extravasation was observed (increased vascular permeability). In addition, the levels of TNF-α (P<0.01) and IL-6 (P<0.01) were significantly increased compared to control. Furthermore, the histopathology of pharyngeal tissue showed hypertrophy of submucosal glands, severe inflammation of the pharynx characterised by presence of mononuclear cells, neutrophils along with haemorrhages and congestion; however, normal control animals showed normal cytoarchitecture of pharynx. Indeed, dexamethasone (0.25, 0.5 and 1 mg/kg, i.v.) and diclofenac (1, 2.5 and 5 mg/kg, i.v.) showed dose-dependent protection against pyridine-induced pharyngitis. Further, the possible mechanism of pyridine-induced pharyngitis is thought to be primarily mediated through phospholipase A2 and cyclooxygenase (COX) pathway.These findings suggest that pyridine-induced pharyngitis is a simple and versatile novel animal model for screening the drugs against non-infectious pharyngitis in rats.