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Antagonism of nicotinic receptors of rat chromaffin cells by N,N,N‐trimethyl‐1‐(4‐ trans ‐stilbenoxy)‐2‐propylammonium iodide: a patch clamp and ligand binding study
Author(s) -
Di Angelantonio Silvia,
Nistri Andrea,
Moretti Milena,
Clementi Francesco,
Gotti Cecilia
Publication year - 2000
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.0703264
Subject(s) - epibatidine , nicotinic agonist , nicotine , chemistry , methyllycaconitine , competitive antagonist , receptor , patch clamp , stereochemistry , biophysics , endocrinology , medicine , antagonist , biology , nicotinic acetylcholine receptor , biochemistry
The effect of the oxystilbene derivative F3 was tested on nAChRs of whole‐cell patch‐clamped rat chromaffin cells in vitro and of rat adrenal gland membranes using 125 I‐epibatidine. F3 (30 n M ) rapidly and reversibly blocked inward currents generated by pulse applications of nicotine, shifting the dose‐response curve to the right in a parallel fashion without changing the maximum response. The action of F3 was voltage insensitive and not due to altered current reversal potential. The R isomer of F3 was more potent (IC 50 =350±30 n M ) than its S ‐enantiomer (IC 50 =1.5±0.3 μ M ). Nicotine‐evoked currents were insensitive to 10 μ M α‐bungarotoxin. Equi‐amplitude currents evoked by nicotine or epibatidine were similarly antagonized by R ‐F3 in a reversible fashion. Epibatidine‐evoked currents readily produced receptor desensitization. Adrenal membranes specifically bound 125 I‐epibatidine with a single population of binding sites endowed with high affinity ( K D =159 p M ) and B max of 6.5±1.3 fmol mg −1 of protein.125 I‐epibatidine binding was specifically displaced by cytisine (K i =68 n M ) or ACh (K i =348 n M ). F3 specifically displaced 125 I‐epibatidine binding although with lower affinity (K i =29.6 μ M ) than in electrophysiological experiments. 125 I‐epibatidine binding to rat adrenal tissue was insensitive to α‐bungarotoxin which readily antagonized 125 I‐epibatidine binding to bovine adrenal tissue. The present results suggest that F3 is a relatively potent and apparently competitive antagonist of nAChRs on rat chromaffin cells. Since previous studies have indicated that F3 targets different subtypes on chick neuronal tissue, it appears that nAChRs display interspecies differences to be considered for drug development studies.British Journal of Pharmacology (2000) 129 , 1771–1779; doi: 10.1038/sj.bjp.0703264