Digitonin-solubilized histamine H1-receptors bind to polyethylenimine-treated glass-fibre filters

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Abstract
The binding of [3H]mepyramine to histamine H1-receptors solublized from guinea-pig cerebellum by 1% digitonin could be assayed by adsorption of the receptor-bound [3H]ligand to glass-fibre filters pretreated with 0.3% polyethylenimine (PEI). Nonspecific binding was higher than in parallel experiments in which the bound and free [3H]ligand was separated by gel-filtration on Sephadex G-25 columns, but the parameters characterizing the inhibition curves were otherwise similar. The PEI-treated filter method could also be used to assay [3H]-(+)-N-methyl-4-methyl-diphenhydramine ([3H]QMDP) binding to solubilized H1-receptors, but the level of non-specific binding was higher and was only satisfactorily defined by icotidine or temelastine. A particular utility of the PEI-treated filter assay will be in measurements of the kinetics of H1-receptor-ligand interactions.