Subcellular Distribution and Pharmacological Identification of M1 Receptors in the Submucosal Nasal Gland Acinar Cells of Guinea Pigs

Abstract

A muscarinic receptor in the submucosal nasal gland acinar cells controls electrolyte and fluid secretion. We investigated the pharmacological identification and the subcellular distribution of Ml receptor using a selective antagonist, pirenzepine (PZ). Intracellular Ca²⁺ concentration ([Ca²⁺]_i) in the isolated acinar cells was measured by a fura-2 method. Addition of PZ inhibited the increase of the [Ca²⁺]_i induced by acetylcholine in a dose-dependent manner, indicating the presence of the Ml receptor. Both fixed section of the nasal septal mucosa and living isolated acinar cells were selectively stained by fluorescence-labeled PZ. Furthermore, confocal laser scanning microscopy revealed that PZ specifically labeled the plasma membrane in the isolated acinar cells. Thus, M1 receptor was proven to be located in the plasma membrane of the submucosal nasal gland acinar cell.