title: Expression of muscarinic acetylcholine receptors M3 and M5 in osteoporosis.
abstract: BACKGROUND
  Cholinergic signaling via muscarinic acetylcholine receptors (mAChR) is known to influence various physiological functions. In bone, M3 mAChR and M5 mAChR were identified on the membrane of osteoblast-like cells. M3 mAChR seems to be particularly relevant for bone physiology, as signaling via this receptor was reported to increase bone formation and decrease bone resorption. Thus, in the present study we investigated the relative mRNA expression of M3 and M5 mAChR in bones of a rat osteoporosis model.
  
  
  METHODS
  Osteoporosis was induced in Sprague-Dawley rats by bilateral ovariectomy and additional feeding of a diet deficient in calcium, vitamins C, D2, D3, and phosphorus, and free of soy and phytoestrogen. After a period of 3, 12, and 14 months, relative mRNA expression of M3 mAChR and M5 mAChR was analyzed in the 11th thoracic vertebra by real-time RT-PCR.
  
  
  RESULTS
  Relative mRNA expression of M3 mAChR was significantly reduced in bones of osteoporotic rats compared to sham operated animals that served as controls. Further, M3 mAChR mRNA expression was significantly down-regulated when comparing 14-month osteoporotic rats to 3-month osteoporotic rats. Relative M5 mAChR mRNA was expressed to a lesser extent than M3 mAChR and did not show significant differences in mRNA expression level between the experimental groups.
  
  
  CONCLUSIONS
  M3 mAChR mRNA expression was reduced upon induction of osteoporosis and progression of disease was associated with further decrease of this receptor, indicating that M3 mAChR is involved in the development and regulation of osteoporosis.
authors.affiliation: Laboratory of Experimental Trauma Surgery, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: Vivien
authors.initials: V
authors.lastname: Kauschke
authors.affiliation: Laboratory of Experimental Trauma Surgery, Justus-Liebig-University Giessen, Giessen, Germany.
authors.forename: Katrin Susanne
authors.initials: KS
authors.lastname: Lips
authors.affiliation: Department of Trauma Surgery, University Hospital of Giessen-Marburg, Giessen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Heiss
authors.affiliation: Department of Trauma Surgery, University Hospital of Giessen-Marburg, Giessen, Germany.
authors.forename: Reinhard
authors.initials: R
authors.lastname: Schnettler
mesh_terms: D000818:Animals; D005260:Female; D005786:Gene Expression Regulation; D010024:Osteoporosis / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D043587:Receptor, Muscarinic M3 / Q000235:genetics*; D043642:Receptor, Muscarinic M5 / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D043587:Receptor, Muscarinic M3; D043642:Receptor, Muscarinic M5