title: Muscarinic receptor immunoreactivity in the superior salivatory nucleus neurons innervating the salivary glands of the rat.
abstract: The superior salivatory nucleus (SSN) contains preganglionic parasympathetic neurons to the submandibular and sublingual salivary glands. Cevimeline, a muscarinic acetylcholine receptor agonist, stimulates the salivary glands and is presently used as sialogogue in the treatment of dry mouth. Since cevimeline passes through the blood-brain barrier, it is also able to act on muscarinic acetylcholine receptors in the central nervous system. Our preliminary experiment using the whole-cell patch-clamp technique has shown that cevimeline excites SSN neurons in rat brain slices, suggesting that SSN neurons have muscarinic acetylcholine receptors; however, it is unclear which subtypes of muscarinic acetylcholine receptors exist in SSN neurons. In the present study, we investigated immunohistochemically muscarinic acetylcholine receptor subtypes, M1 receptor (M1R), M2R, M3R, M4R, and M5R in SSN neurons. SSN neurons innervating the salivary glands, retrogradely labeled with a fluorescent tracer from the chorda-lingual nerve, mostly expressed M3R immunoreactivity (-ir) (92.3%) but not M1R-ir. About half of such SSN neurons also showed M2R- (40.1%), M4R- (54.0%) and M5R-ir (46.0%); therefore, it is probable that SSN neurons co-express M3R-ir with at least two of the other muscarinic receptor subtypes. This is the first report to show that SSN neurons contain muscarinic acetylcholine receptors.
authors.affiliation: Department of Orthodontics, Kagoshima University Medical and Dental Hospital, Kagoshima 890-8544, Japan.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Ueda
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Mitoh
authors.forename: Masako
authors.initials: M
authors.lastname: Fujita
authors.forename: Motoi
authors.initials: M
authors.lastname: Kobashi
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamashiro
authors.forename: Tomosada
authors.initials: T
authors.lastname: Sugimoto
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ichikawa
authors.forename: Ryuji
authors.initials: R
authors.lastname: Matsuo
mesh_terms: D000818:Animals; D007150:Immunohistochemistry; D008297:Male; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D010275:Parasympathetic Nervous System / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011976:Receptors, Muscarinic / Q000145:classification / Q000378:metabolism*; D012249:Rhombencephalon / Q000166:cytology / Q000378:metabolism*; D012469:Salivary Glands / Q000294:innervation* / Q000502:physiology
chemical_list: D011976:Receptors, Muscarinic