Bruns R F, Lu G H, Pugsley T A
Mol Pharmacol. 1986 Apr;29(4):331-46.
[3H]NECA (1-(6-amino-9H-purin-9-yl)-1-deoxy-N-ethyl-beta-D-ribofuronamide) is known to bind to both the A1 and A2 subtypes of adenosine receptor in rat striatal membranes. In order to study the putative A2 component of [3H]NECA binding, we examined several compounds for the ability to selectively eliminate the A1 component of binding; N6-cyclopentyladenosine was found to give the most satisfactory results. Binding of [3H]NECA in the presence of 50 nM N6-cyclopentyladenosine was characterized. The rank order of potency for inhibition of [3H]NECA binding was NECA much greater than 2-chloroadenosine greater than N6-[(R)-1-methyl-2-phenyl-ethyl]adenosine (R-PIA) greater than N6-cyclohexyladenosine greater than S-PIA, indicating that binding was to an A2 adenosine receptor. When affinities of compounds in [3H]NECA binding to A2 receptors were compared to their affinities in [3H]N6-cyclohexyladenosine binding to A1 receptors, N6-cyclopentyladenosine was the most A1-sensitive agonist (A1 Ki, 0.59 nM; A2 Ki, 460 nM; Ki ratio, 780), whereas the selective coronary vasodilator 2-(phenylamino)adenosine was the most A2-selective agonist (A1, 560 nM; A2, 120 nM; ratio, 0.21). The antagonist 8-cyclopentyltheophylline had considerable A1 selectivity (A1, 11 nM; A2, 1400 nM; ratio, 130), whereas alloxazine had slight A2 selectivity (A1, 5200 nM; A2, 2700; ratio, 0.52). [3H]NECA binding to A2 receptors was highest in striatum but was detectable at much lower levels in each of seven other brain areas. The regional distribution of [3H]NECA binding and the affinities of adenosine agonists and antagonists for inhibition of binding indicate that the site labeled by [3H]NECA belongs to the high affinity, or A2a, subclass of A2 receptor.
已知[3H]NECA（1-(6-氨基-9H-嘌呤-9-基)-1-脱氧-N-乙基-β-D-核糖呋喃酰胺）能与大鼠纹状体膜中的腺苷受体A1和A2亚型结合。为了研究[3H]NECA结合中假定的A2成分，我们检测了几种化合物选择性消除结合的A1成分的能力；发现N6-环戊基腺苷给出了最令人满意的结果。对在50 nM N6-环戊基腺苷存在下[3H]NECA的结合进行了表征。抑制[3H]NECA结合的效力顺序为NECA远大于2-氯腺苷大于N6-[(R)-1-甲基-2-苯基-乙基]腺苷（R-PIA）大于N6-环己基腺苷大于S-PIA，表明结合是与A2腺苷受体。当比较[3H]NECA结合中化合物与A2受体的亲和力与其在[3H]N6-环己基腺苷结合中与A1受体的亲和力时，N6-环戊基腺苷是对A1最敏感的激动剂（A1 Ki，0.59 nM；A2 Ki，460 nM；Ki比值，780），而选择性冠状动脉扩张剂2-(苯氨基)腺苷是对A2最具选择性的激动剂（A1，560 nM；A2，120 nM；比值，0.21）。拮抗剂8-环戊基茶碱具有相当的A1选择性（A1，11 nM；A2，1400 nM；比值，130），而异嗪二酮具有轻微的A2选择性（A1，5200 nM；A2，2700 nM；比值，0.52）。[3H]NECA与A2受体的结合在纹状体中最高，但在其他七个脑区中的水平要低得多。[3H]NECA结合的区域分布以及腺苷激动剂和拮抗剂对结合抑制的亲和力表明，[3H]NECA标记的位点属于A2受体的高亲和力或A2a亚类。
