Kennedy C, Burnstock G
Eur J Pharmacol. 1984 May 4;100(3-4):363-8. doi: 10.1016/0014-2999(84)90014-1.
The effects of adenosine (ADO) and of the adenosine analogues 5'-N-ethylcarboxamideadenosine (NECA), 2-chloroadenosine (2-CADO), L- and D-phenylisopropyladenosine (L- and D-PIA) and N6-cyclohexyladenosine (CHA) were compared on the contractile response of the isolated rat portal vein to perivascular adrenergic nerve stimulation. The order of potency at 20% inhibition of control values was NECA greater than or equal to 2-CADO = L-PIA greater than D-PIA = CHA greater than ADO. At this level of inhibition only D-PIA had a significant inhibitory effect against a matched concentration of exogenous NA. The difference in potency between L-PIA and D-PIA was approximately 3-fold. 8-Phenyltheophylline, a potent P1-purinoceptor antagonist, had a direct inhibitory effect on the tissue per se and therefore could not be used to antagonise these compounds. It is concluded that NECA, 2-CADO, L-PIA, D-PIA, CHA and ADO mediate their inhibitory effect in the rat portal vein via a prejunctional P1-purinoceptor which displays characteristics of the A2 classification, in contrast to that found to date in other adrenergic and cholinergic nerve terminals where it displays characteristics of the A1 classification.
比较了腺苷（ADO）以及腺苷类似物5'-N-乙基甲酰胺腺苷（NECA）、2-氯腺苷（2-CADO）、L-和D-苯异丙基腺苷（L-和D-PIA）与N6-环己基腺苷（CHA）对离体大鼠门静脉对血管周围肾上腺素能神经刺激的收缩反应的影响。在抑制对照值20%时的效价顺序为NECA≥2-CADO = L-PIA＞D-PIA = CHA＞ADO。在此抑制水平下，只有D-PIA对外源性去甲肾上腺素（NA）的匹配浓度有显著抑制作用。L-PIA和D-PIA之间的效价差异约为3倍。8-苯基茶碱是一种强效的P1嘌呤受体拮抗剂，对组织本身有直接抑制作用，因此不能用于拮抗这些化合物。得出的结论是，NECA、2-CADO、L-PIA、D-PIA、CHA和ADO通过一种突触前P1嘌呤受体介导其在大鼠门静脉中的抑制作用，该受体表现出A2分类的特征，这与迄今为止在其他肾上腺素能和胆碱能神经末梢中发现的表现出A1分类特征的情况形成对比。
