title: Interaction of 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride, ryanodine and procaine with muscarinic cholinergic M2 receptor sites in smooth muscle.
abstract: We have characterized muscarinic cholinergic receptor sites and interaction of various modulators of intracellular Ca mobilization, such as 8-(N,N-diethylamino)octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8), ryanodine, procaine and related drugs with the receptor sites, using a binding assay method with [3H]quinuclidinyl benzilate [( 3H]QNB) in guinea pig tenia cecum membrane fraction. [3H]QNB bound to a single population of sites, and the binding profile of pirenzepine suggest that the receptor sites are probably the M2 type. All the test drugs examined except for ryanodine displaced the [3H]QNB binding, and the slope factors were not different from unity. Affinities of these drugs were comparable to the concentrations usually used to modulate intracellular Ca mobilization. A Scatchard plot of [3H]QNB binding in the presence of TMB-8 or procaine showed that the apparent dissociation constant for [3H]QNB was increased without change in maximum binding. Neither TMB-8 nor procaine had any effect on the rate of dissociation of [3H]QNB from the steady-state complex. These results suggest that TMB-8 and procaine, and possibly other drugs, may interact directly with the muscarinic cholinergic M2 receptor sites in a competitive manner. In contrast, ryanodine had no effect on the [3H]QNB binding up to at least 100 microM. No interaction of ryanodine with M2 receptor sites lends a further support that the drug could be a useful probe for studying intracellular Ca mobilization.
authors.affiliation: Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Hisayama
authors.forename: I
authors.initials: I
authors.lastname: Takayanagi
authors.forename: N
authors.initials: N
authors.lastname: Kumagai
authors.forename: H
authors.initials: H
authors.lastname: Kubo
mesh_terms: D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D005260:Female; D005707:Gallic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000378:metabolism; D009130:Muscle, Smooth / Q000378:metabolism; D011343:Procaine / Q000494:pharmacology*; D011813:Quinuclidinyl Benzilate / Q000378:metabolism; D011976:Receptors, Muscarinic / Q000187:drug effects* / Q000378:metabolism; D012433:Ryanodine / Q000494:pharmacology*
chemical_list: D000470:Alkaloids; D011976:Receptors, Muscarinic; D012433:Ryanodine; D011343:Procaine; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D011813:Quinuclidinyl Benzilate; D002118:Calcium