Decreased binding affinity of olanzapine and clozapine for human muscarinic receptors in intact clonal cells in physiological medium.
The binding affinity of olanzapine, clozapine and atropine for muscarinic receptor subtypes in clonal Chinese hamster ovary (CHO) cell lines was compared in intact cells in physiological media to disrupted cells in hypotonic buffer. The affinity of olanzapine and clozapine, but not atropine, for muscarinic receptor subtypes (M(1)-M(5)) was significantly reduced in intact cells in physiological medium compared to disrupted cells in hypotonic buffer. The affinity of olanzapine for muscarinic M(1) receptors was most affected with a reduction of K(i) value from 2.5 to 73 nM in intact cells. These data suggest that the affinity of olanzapine and clozapine for muscarinic receptors have been significantly overestimated.
Bymaster
F P
FP
Neuroscience Research Division, Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, IN 46285-0510, USA. f.bymaster@lilly.com
Falcone
J F
JF
D000818:Animals; D001569:Benzodiazepines; D001667:Binding, Competitive / Q000187:drug effects; D016466:CHO Cells; D003024:Clozapine / Q000378:metabolism* / Q000494:pharmacology; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007038:Hypotonic Solutions / Q000494:pharmacology; D007552:Isotonic Solutions / Q000494:pharmacology; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D019832:N-Methylscopolamine / Q000378:metabolism; D000077152:Olanzapine; D010890:Pirenzepine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D011869:Radioligand Assay; D011976:Receptors, Muscarinic / Q000235:genetics / Q000378:metabolism*; D014316:Tritium
D007038:Hypotonic Solutions; D007552:Isotonic Solutions; D011976:Receptors, Muscarinic; D014316:Tritium; D001569:Benzodiazepines; D010890:Pirenzepine; D003024:Clozapine; D000077152:Olanzapine; D019832:N-Methylscopolamine