Regulation of muscarinic receptor binding by guanine nucleotides and N-ethylmaleimide

F. J. Ehlert, W. R. Roeske, H. I. Yamamura

Research output: Contribution to journalArticle

48 Scopus citations

Abstract

The regulation of muscarinic receptor binding by guanine nucleotides and N-ethylmaleimide (NEM) was investigated using the agonist ligand, [3H] cis methyldioxolane ([3H]CD). Characterization studies on rat forebrain homogenates showed that [3H]CD binding was linear with tissue concentration and was unaffected by a change in pH form 5.5 to 8.0. The regional variation in [3H]CD binding in the rat brain correlated generally with [3H](-)3-quinuclidinyl benzilate ([3H](-)QNB) binding, although the absolute variation in binding was somewhat less. At a concentration of 100 μM, the GTP analogue, guanyl-5'-yl imidodiphosphate [Gpp(NH)p], caused a 43-77% inhibition of [3H]CD binding in the corpus striatum, ileum, and heart. The results of binding studies using several Gpp(NH)p concentrations demonstrated that the potency of this guanine nucleotide for inhibition of [3H]CD binding was greater in the heart than in the ileum. In contrast to its effects on [3H]CD binding, Gpp(NH)p caused an increase in [3H](-)QNB binding in the heart and ileum and no change in [3H](-)QNB binding in the corpus striatum. When measured by competitive inhibition of [3H](-)QNB binding to the longitudinal muscle of the ileum, Gpp(NH)p (100μM) caused an increase in the IC50 values of a series of agonists in a manner that was correlated with the efficacy of these compounds. The results of binding studies in NEM treated forebrain homogenates revealed an enhancement of [3H]CD binding by NEM.

Original languageEnglish (US)
Pages (from-to)149-162
Number of pages14
JournalJournal of Supramolecular and Cellular Biochemistry
Volume14
Issue number2
DOIs
StatePublished - Jan 1 1980
Externally publishedYes

ASJC Scopus subject areas

  • Biochemistry

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