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A study of the actions of P 1 ‐purinoceptor agonists and antagonists in the mouse vas deferens in vitro
Author(s) -
Blakeley A.G.H.,
Dunn P.M.,
Petersen S.A.
Publication year - 1988
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.1476-5381.1988.tb11497.x
Subject(s) - vas deferens , purinergic receptor , adenosine , agonist , endocrinology , medicine , chemistry , adenosine deaminase , adenosine receptor , excitatory postsynaptic potential , receptor , inhibitory postsynaptic potential , biology
1 We have examined the effects of purinoceptor agonists and antagonists on the mechanical ‘twitch’ response, excitatory junction potential (e.j.p.) amplitude and [ 3 H]‐noradrenaline overflow in the mouse vas deferens. 2 The agonist profile for inhibition of the mechanical response was N 6 ‐([R]‐2‐phenylisopropyl)adenosine ( l ‐PIA) ⋍ N 6 ‐cyclohexyladenosine (CHA) > 5′ N‐ethylcarboxamidoadenosine (NECA) > 2‐chloroadenosine (2ClA) ⋍ N 6 ‐([S]‐2‐phenylisopropyl)adenosine ( d ‐PIA). 3 The P 1 ‐purinoceptor agonists inhibited the e.j.p. with an agonist profile of CHA > l ‐PIA NECA > 2ClA. 4 2ClA inhibited [ 3 H]‐noradrenaline overflow with an EC 50 of 1.2 μ m which was not significantly different from the values for inhibition of the e.j.p. and the mechanical response. 5 The inhibitory action of 2ClA on the mechanical response was antagonized by 5 μ m 8‐phenyltheophylline (8‐PT). However, neither blockade of P 1 ‐purinoceptors by 8‐PT nor increasing the rate of degradation of endogenous adenosine by addition of adenosine deaminase had any effect on the mechanical response per se. 8‐PT (5 μ m ) also failed to alter the e.j.p. amplitude or [ 3 H]‐noradrenaline overflow. 6 These results indicate that there are P 1 ‐purinoceptors present on sympathetic nerve terminals of the mouse vas deferens which are more like A 1 ‐ than A 2 ‐receptors, but may be better classified as being of the A 3 ‐subtype (Ribeiro & Sebastiao, 1986). These receptors are not normally involved in the feedback regulation of transmitter release in this tissue.