title: Loss of muscarinic M4 receptors in spinal cord of arthritic rats: implications for a role of M4 receptors in pain response.
abstract: Changes in the levels of muscarinic M4 receptors in spinal cord of acute and chronic arthritic rats (animal models of pain) were studied by receptor autoradiography using muscarinic M4 receptor subtype selective ligand. Arthritis was induced in female Lewis rats by single intradermal injection of heat-killed Mycobacterium butyricum and sacrificed 12 days (acute group) and 30 days (chronic and control groups) after induction of arthritis. Our results demonstrate significant reduction in the level of M4 receptors in the spinal cord (Rexed laminae I-X) of acute and chronic arthritic rats compared to controls. These findings suggest that the muscarinic M4 receptor subtype may be involved in cholinergic mechanisms of analgesia.
authors.affiliation: Section of Experimental Geriatrics, NEUROTEC, Karolinska Institute, 141 86 Huddinge, Sweden.
authors.forename: Ezra
authors.initials: E
authors.lastname: Mulugeta
authors.forename: Nahid
authors.initials: N
authors.lastname: El-Bakri
authors.forename: Evert
authors.initials: E
authors.lastname: Karlsson
authors.forename: Adlan
authors.initials: A
authors.lastname: Elhassan
authors.forename: Abdu
authors.initials: A
authors.lastname: Adem
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000208:Acute Disease; D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism* / Q000503:physiopathology; D002908:Chronic Disease; D015536:Down-Regulation / Q000502:physiology; D005260:Female; D010146:Pain / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D043588:Receptor, Muscarinic M4 / Q000378:metabolism*; D013116:Spinal Cord / Q000378:metabolism*
chemical_list: D043588:Receptor, Muscarinic M4; D000109:Acetylcholine