title: The use of a modified [3H]4-DAMP radioligand binding assay with increased selectivity for muscarinic M3 receptor shows that cortical CHRM3 levels are not altered in mood disorders.
abstract: [(3)H]4-DAMP is a radioligand that has been used to quantify levels of the muscarinic receptor CHRM3 protein in situ. However, in addition to high affinity binding to CHRM3, [(3)H]4-DAMP binds with low affinity to CHRM1 confounding the potential to discriminate between changes in these two muscarinic receptors. We have developed a [(3)H]4-DAMP binding assay, optimised for measuring CHRM3 protein levels in the cortex, with minimal selectivity towards CHRM1. The selectivity of our assay towards CHRM3 was confirmed using recombinant receptor-expressing, cell lysate preparations. [(3)H]4-DAMP binding levels were similar between wildtype and CHRM1 knockout mice, confirming that the amount of [(3)H]4-DAMP binding to CHRM1 was negligible. We used this assay to measure CHRM3 protein levels in the frontal pole, obtained post-mortem from subjects with bipolar disorder (n = 15), major depressive disorder (n = 15) and matched controls (n = 20) and showed that [(3)H]4-DAMP binding was not altered in either bipolar disorder or major depressive disorder. Western blotting confirmed that CHRM3 protein levels were unchanged in these subjects.
authors: Molecular Psychiatry Laboratory, The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, Australia; Department of Psychiatry, the University of Melbourne, Parkville, VIC, Australia.
authors: Won Je
authors: WJ
authors: Jeon
authors: Andrew S
authors: AS
authors: Gibbons
authors: Brian
authors: B
authors: Dean
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D002540:Cerebral Cortex / Q000187:drug effects* / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008875:Middle Aged; D019964:Mood Disorders / Q000000981:diagnostic imaging / Q000473:pathology*; D018727:Muscarinic Antagonists / Q000493:pharmacokinetics*; D010880:Piperidines / Q000493:pharmacokinetics*; D010890:Pirenzepine / Q000493:pharmacokinetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D011869:Radioligand Assay; D011877:Radionuclide Imaging; D043643:Receptor, Muscarinic M1; D043587:Receptor, Muscarinic M3 / Q000235:genetics / Q000378:metabolism*; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism; D014316:Tritium / Q000493:pharmacokinetics
chemical_list: C086088:CHRM1 protein, human; D018727:Muscarinic Antagonists; D010880:Piperidines; D043643:Receptor, Muscarinic M1; D043587:Receptor, Muscarinic M3; D011976:Receptors, Muscarinic; D014316:Tritium; D010890:Pirenzepine; C042375:4-diphenylacetoxy-1,1-dimethylpiperidinium
keywords: 4-DAMP; 4-diphenylacetoxy-N-methylpiperidine; BPD; Bipolar disorder; CHRM; CON; ETE; IC; MDD; Major depressive disorder; Muscarinic receptors; Radioligand binding; [(3)H]4-DAMP; bipolar disorder; cholinergic muscarinic receptor; estimated tissue equivalent; healthy control; internal control; major depressive disorder