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The effects of brucine and alcuronium on the inhibition of [ 3 H]acetylcholine release from rat striatum by muscarinic receptor agonists
Author(s) -
Doležal Vladimír,
Tuček Stanislav
Publication year - 1998
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1038/sj.bjp.0701966
Subject(s) - oxotremorine , muscarinic acetylcholine receptor , chemistry , acetylcholine , muscarinic acetylcholine receptor m4 , pharmacology , muscarinic acetylcholine receptor m1 , muscarinic acetylcholine receptor m2 , allosteric regulation , striatum , inhibitory postsynaptic potential , acetylcholine receptor , pirenzepine , receptor , endocrinology , medicine , biochemistry , biology , dopamine
1 Radioligand binding experiments indicate that the affinity of muscarinic receptors for their agonists may be enhanced by allosteric modulators. We have now investigated if brucine can enhance the inhibitory effects of muscarinic receptor agonists on the electrically evoked release of [ 3 H]acetylcholine ([ 3 H]ACh) from superfused slices of rat striatum. 2 The evoked release of [ 3 H]ACh was inhibited by all agonists tested (i.e., furmethide, oxotremorine‐M, bethanechol and oxotremorine). 3 Brucine enhanced the inhibitory effects of furmethide, oxotremorine‐M and bethanechol on the evoked [ 3 H]ACh release without altering the inhibitory effect of oxotremorine. 4 Alcuronium was applied for comparison and found to diminish the inhibitory effect of furmethide on the evoked [ 3 H]ACh release. 5 The results demonstrate that it is possible both to enhance and diminish the functional effects of muscarinic receptor agonists by allosteric modulators. 6 The direction of the observed effects of brucine and alcuronium on [ 3 H]ACh release fully agrees with the effects of these modulators on the affinities of human M 4 receptors for furmethide, oxotremorine‐M, bethanechol and oxotremorine, as described by Jakubík et al. (1997). This supports the view that the presynaptic muscarinic receptors responsible for the autoinhibition of ACh release in rat striatum belong to the M 4 muscarinic receptor subtype.British Journal of Pharmacology (1998) 124 , 1213–1218; doi: 10.1038/sj.bjp.0701966