Novel experimental model of non-infectious pharyngitis in rats.

INTRODUCTION: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.

Ameliorative effect of Koflet formulations against pyridine-induced pharyngitis in rats.

In present study two formulations of Koflet (syrup and lozenges) were evaluated against pyridine-induced pharyngitis in rats. Topical application of 10% pyridine showed extravasation of Evans blue stain as a characteristic feature of on-going inflammation. In addition, the levels of TNF-α (p < 0.01) and IL-6 (p < 0.01) were significantly increased compared to control. Further, histopathology of the pharyngeal tissue showed submucosal gland hypertrophy, severe mucosal inflammation characterized by presence of mononuclear cells and neutrophils along with haemorrhages and congestion; however, saline applied animals (normal control) showed normal cytoarchitecture of the pharynx. Interestingly, pre-treatment with dexamethasone (1 mg/kg, p.o.), Koflet lozenges (KL) (500 and 1000 mg/kg, p.o.) and Koflet syrup (KS) (2 and 4 ml/kg, p.o.) for 7 days showed significant and dose dependent protection by decreasing the EB dye extravasation, and serum levels of TNF-α and IL-6. In addition, histopathological findings have further supported the protective effect of Koflet formulations. These findings suggest that, both Koflet syrup and Koflet lozenges are highly effective in treating non-infectious type of pharyngitis. Among the two formulations KS was found to be more potent than KL, and possible mechanism of action thought to be mediating through inhibition of TNF-α and/or phospholipids-arachidonic acid pathway.