title: Simvastatin reverses the downregulation of M1/4 receptor binding in 6-hydroxydopamine-induced parkinsonian rats: the association with improvements in long-term memory.
abstract: BACKGROUND
  It is believed that muscarinic M1/4 receptors are closely correlated to the dopaminergic system and are strongly involved in the pathogenesis of Parkinson's disease (PD). In addition to regulating lipid metabolism and protection from stroke, statins have been used to regulate the declined cognition. We aimed to explore the regional changes in M1/4 receptors in the 6-hydroxydopamine (6-OHDA)-lesioned rat brain.
  
  
  METHODS
  PD rat model was set up by injecting 6-OHDA into the unilateral medial forebrain bundle; while simvastatin (10mg/kg/day) or saline was orally administrated for 3weeks, respectively. Long-term memory was measured using the Morris water maze. [(3)H]pirenzepine binding autoradiography was applied to investigate the alterations of M1/4 receptors in the PD rat brains.
  
  
  RESULTS
  6-OHDA induced long-term memory deficits along with downregulation of M1/4 receptors in the hippocampus, the medial amygdala, the posteromedial cortical and the piriform cortex; simvastatin administration significantly ameliorated the impaired memory and reversed the downregulation of M1/4 receptors in the examined brain regions. Profound positive correlations were verified between the decline in long-term memory activity and the restoration of M1/4 receptors in different brain regions after simvastatin treatment.
  
  
  CONCLUSIONS
  Our results provide strong evidence that M1/4 receptor modulation after simvastatin administration did, at least partially, contribute to the improvement in the long-term memory in 6-OHDA-induced PD rats. These results provide a possible mechanism for simvastatin treatment in psycho-neurological diseases such as PD via M1/4 receptors.
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China; Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW 2522, Australia. Electronic address: denniswq@yahoo.com.
authors.forename: Q
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China.
authors.forename: X
authors.initials: X
authors.lastname: Wei
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China.
authors.forename: H
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China.
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China.
authors.forename: J
authors.initials: J
authors.lastname: Liao
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China.
authors.forename: X
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Neurology, The Third Affiliated Hospital of Sun Yat-Sen University, Tianhe Road 600, Guangzhou, Guangdong 510630, PR China.
authors.forename: B
authors.initials: B
authors.lastname: Qin
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW 2522, Australia.
authors.forename: Y
authors.initials: Y
authors.lastname: Yu
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW 2522, Australia.
authors.forename: C
authors.initials: C
authors.lastname: Deng
authors.affiliation: Department of Neurology, Xiangya Hospital of Central South University, Changsha, Hunan 410008, PR China.
authors.forename: B
authors.initials: B
authors.lastname: Tang
authors.affiliation: Centre for Translational Neuroscience, School of Health Sciences, University of Wollongong, NSW 2522, Australia.
authors.forename: X-F
authors.initials: XF
authors.lastname: Huang
mesh_terms: D000818:Animals; D001921:Brain / Q000187:drug effects; D004195:Disease Models, Animal; D015536:Down-Regulation / Q000187:drug effects*; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000627:therapeutic use*; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D057567:Memory, Long-Term / Q000187:drug effects*; D018727:Muscarinic Antagonists / Q000493:pharmacokinetics; D016627:Oxidopamine / Q000633:toxicity; D010300:Parkinson Disease / Q000150:complications / Q000188:drug therapy* / Q000209:etiology; D010890:Pirenzepine / Q000493:pharmacokinetics; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D043643:Receptor, Muscarinic M1 / Q000378:metabolism*; D043588:Receptor, Muscarinic M4 / Q000378:metabolism*; D019821:Simvastatin / Q000627:therapeutic use*; D013565:Sympatholytics / Q000633:toxicity; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D018727:Muscarinic Antagonists; D043643:Receptor, Muscarinic M1; D043588:Receptor, Muscarinic M4; D013565:Sympatholytics; D014316:Tritium; D010890:Pirenzepine; D016627:Oxidopamine; D019821:Simvastatin
keywords: M1/4 receptors; Parkinson’s disease; memory; simvastatin