title: Search for the pharmacophore of bispyridinium-type allosteric modulators of muscarinic receptors.
abstract: The bis(dichlorobenzyl) ether of the bispyridinium oxime TMB 4 stabilizes antagonist binding to M2-cholinoceptors which is indicative of an allosteric action. More than 10 derivatives of the lead compound were synthesized to investigate structure-activity relationships. The allosteric potency of the compounds was indicated by the concentrations which retarded the rate of dissociation of [3H]N-methylscopolamine from porcine cardiac cholinoceptors by a factor of 2 (EC50). Compared with TMB 4, the bis(dichlorobenzyl) derivative 4a displayed a more than 200-fold higher potency (EC50 = 4.7 microM). One of the dichlorobenzyl groups could be replaced by a methyl group without loss of activity (EC50 = 4.5 microM). Further shortening of this end of the molecule was accompanied by a moderate decline in potency to a minimum of EC50 = 26 microM. The second quaternary nitrogen was not a prerequisite for an allosteric activity. It is concluded that one half of the lead compound is pivotal for an interaction with the allosteric site of the M2-cholinoceptor, whereas the opposite end of the molecule modulates the allosteric activity.
authors.affiliation: Institute of Pharmacy, University of Bonn, FRG.
authors.forename: M H
authors.initials: MH
authors.lastname: Botero Cid
authors.forename: U
authors.initials: U
authors.lastname: Holzgrabe
authors.forename: E
authors.initials: E
authors.lastname: Kostenis
authors.forename: K
authors.initials: K
authors.lastname: Mohr
authors.forename: C
authors.initials: C
authors.lastname: Tränkle
mesh_terms: D000494:Allosteric Regulation; D000818:Animals; D066298:In Vitro Techniques; D007700:Kinetics; D009206:Myocardium / Q000378:metabolism; D019832:N-Methylscopolamine; D011726:Pyridinium Compounds / Q000378:metabolism / Q000494:pharmacology*; D011869:Radioligand Assay; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D012602:Scopolamine Derivatives / Q000378:metabolism; D013329:Structure-Activity Relationship; D013552:Swine
chemical_list: D011726:Pyridinium Compounds; D011976:Receptors, Muscarinic; D012602:Scopolamine Derivatives; D019832:N-Methylscopolamine