title: Problematical binding of [3H]5-hydroxytryptamine to rat gut myenteric membranes.
abstract: The binding of [3H]5-hydroxytryptamine (5-HT) to rat enteric membranes was inhibited by the inclusion of 5-HT 2-methyl-5-HT, 5-hydroxytryptophan, N,N,N-triethyltryptamine and 2-Br-N,N-diethyltryptamine in the incubation buffer. In contrast, tryptamine, 5-methoxytryptamine and 2-methyl-N,N-diethyltryptamine enhanced binding. Ascorbate and dithiothreitol facilitated and reduced binding at low and high concentrations respectively. Methysergide, tropisetron, paroxetine and pargyline failed to modify binding. However, following the establishment of [3H]5-HT binding, the subsequent addition of 5-HT and other agents failed to displace [3H]5-HT binding. Heat treatment of the membrane preparation also failed to modify [3H]5-HT binding. The latter findings of an irreversible and heat-insensitive binding indicate that the apparently high affinity 'specific' labelling of [3H]5-HT to rat enteric membranes does not represent receptor-bound [3H]5-HT. The complex interaction between [3H]5-HT and other agents may reflect oxidative events and problematic binding.
authors.affiliation: Postgraduate Studies in Pharmacology, School of Pharmacy, University of Bradford, West Yorkshire, UK.
authors.forename: T J
authors.initials: TJ
authors.lastname: Williams
authors.forename: B
authors.initials: B
authors.lastname: Costall
authors.forename: R J
authors.initials: RJ
authors.lastname: Naylor
mesh_terms: D008735:5-Methoxytryptamine / Q000494:pharmacology; D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology; D001665:Binding Sites / Q000187:drug effects; D004229:Dithiothreitol / Q000494:pharmacology; D006150:Guanine Nucleotides / Q000494:pharmacology; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000187:drug effects / Q000378:metabolism*; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D004130:N,N-Dimethyltryptamine / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D014363:Tryptamines / Q000494:pharmacology
chemical_list: D006150:Guanine Nucleotides; D014363:Tryptamines; D012701:Serotonin; D008735:5-Methoxytryptamine; C035668:N-methyltryptamine; C045918:2-methyl-5-HT; D001205:Ascorbic Acid; D004229:Dithiothreitol; D004130:N,N-Dimethyltryptamine