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Characterization of the adenosine receptors of the rat superior cervical ganglion
Author(s) -
Connolly G.P.,
Stone T.W.,
Brown F.
Publication year - 1993
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 - 10.1111/j.1476-5381.1993.tb13891.x
Subject(s) - adenosine , muscarine , adenosine receptor , superior cervical ganglion , depolarization , chemistry , hyperpolarization (physics) , agonist , antagonist , medicine , endocrinology , adenosine a1 receptor , pharmacology , receptor , biology , biochemistry , stereochemistry , muscarinic acetylcholine receptor , nuclear magnetic resonance spectroscopy
1 Adenosine analogues caused hyperpolarization and inhibition of the depolarizing response to muscarine of the rat isolated superior cervical ganglion (SCG) measured by a ‘grease gap’ recording technique. The receptors mediating these responses have been characterized by use of a range of selective adenosine analogues and adenosine receptor antagonists. 2 In decreasing order of potency N 6 ‐cyclopentyladenosine (CPA), 2‐chloroadenosine (2CA), adenosine, 2‐phenylaminoadenosine (PAA), caused concentration‐dependent hyperpolarizations whilst N 6 ‐(9‐fluorenylmethyl)adenosine (PD 117,413) was inactive at up to 100 μ m . 3 The order of potency of adenosine analogues in depressing depolarization caused by a submaximal concentration of muscarine (100 n m ) was: CPA > R ‐PIA = 2C A > NEC A > S‐PIA > BZA > adenosine > PAA, where R ‐ and S‐PIA = R (−)‐ and S(+)‐N 6 ‐(2‐phenylisopropyl)adenosine, NECA = 5′N‐ethylcarboxamidoadenosine and BZA = N 6 ‐benzyladenosine. PD 117,413 was inactive at concentrations up to 100 μ m . The maximum inhibitions of the muscarine‐induced depolarization by CPA, 2CA, NECA and BZA were similar. R ‐PIA, S‐PIA and PAA produced similar maximal inhibitions which were significantly smaller than those produced by CPA. 4 Hyperpolarizations caused by adenosine were antagonized by the P 1 ‐purinoceptor selective antagonist 1,3‐dimethyl‐8‐phenylxanthine (8PT) and by the selective A 1 ‐adenosine receptor antagonist, 1,3‐dipropyl‐8‐(4‐((2aminoethyl)amino)carbonylmethyloxyphenyl)xanthine (XAC). Hyperpolarizations caused by CPA, adenosine and PAA were antagonized by the A 1 ‐selective antagonist, 8‐cyclopentyl‐1,3‐dipropylxanthine (DPCPX) but not by the A 2 ‐selective antagonist, 3,7‐dimethyl‐1‐propargylxanthine (DMPX). 5 Inhibition of the muscarinic‐induced depolarization by CPA was antagonized by 8PT and DPCPX but not by DMPX. 6 It is concluded that the neurones of the rat SCG possess P 1 ‐purinoceptors of the A 1 ‐adenosine receptor subtype which mediate hyperpolarization and inhibition of depolarization caused by muscarine.