Muscarinic cholinergic receptors in minor salivary gland tissues of patients with oral lichen planus: A case-control study.

BACKGROUND: Oral lichen planus (OLP) is a common, chronic immunological and inflammatory condition. Many of the OLP patients complain of xerostomia. The M3 muscarinic cholinergic receptors (MR3) are the main receptors in the salivary glands responsible for water secretion into the saliva. This study aimed to assess the level of M3 muscarinic cholinergic receptors in minor salivary glands of OLP patients. METHODS: This case-control cross-sectional study evaluated 40 OLP patients and 22 controls. All participants completed two questionnaires (xerostomia and xerostomia inventory). Stimulated and unstimulated saliva samples were collected. The saliva flow rate was calculated by dividing the saliva volume (in milliliters) by time (in minutes). Six minor salivary glands were also surgically removed from the lower lip of patients and controls, and weighed using a digital scale with 10(-4) g accuracy. They were then frozen at -80 degrees C, and the level of M3 receptors of the glands was determined using the ELISA kit. RESULTS: The unstimulated and stimulated saliva flow rate was significantly lower in OLP patients. The xerostomia inventory score was significantly higher in the OLP group. The level of M3 muscarinic receptors in minor salivary glands of OLP patients was significantly higher than that in controls. CONCLUSIONS: It may be concluded that the reduction in saliva flow significantly increases the number of M3 receptors in an attempt to compensate for this shortage and prevent xerostomia (compensatory upregulation).