Sympathetically mediated contractions of smooth muscle cells in the vasa deferentia are mediated by neuronally released adenosine 5′-triphosphate (ATP) and noradrenaline, which stimulate P2X1-purinoceptors and α_1A-adrenoceptors, respectively. This process is crucial for sperm transport, as demonstrated in knockout mouse studies where simultaneous genetic deletion of P2X1-purinoceptors and α_1A-adrenoceptors resulted in male infertility. We hypothesize that dual pharmacological antagonism of these two receptors could inhibit sperm transport sufficiently to provide a novel nonhormonal method of male contraception. To generate a suitable P2X1-purinoceptor antagonist, substituents were introduced on the phenyl moiety of 2-phenyl-5,6,7,8-tetrahydroquinoxaline to create a series of analogues that were tested for P2X1-purinoceptor antagonism in isolated preparations of rat vas deferens. Novel compounds were initially screened for their ability to attenuate contractile responses to electrical field stimulation (EFS: 60 V, 0.5 ms, 0.2 Hz). The addition of polar substituents to the meta, but not ortho, position markedly increased the inhibition of contractions, as did the addition of both polar and aliphatic substituents to the para position. Di-substituted compounds were also synthesized and tested, resulting in a compound 31 (2-hydroxy, 4-fluoro), which exhibited the greatest potency, with an IC₅₀ of 14 μM (95% confidence limits: 12–16 μM). Additionally, compound 31 noncompetitively antagonized contractions mediated by exogenously administered αß-methylene ATP (10 nM–30 μM) but had no inhibitory effect on contractions mediated by exogenously administered noradrenaline (30 nM–100 μM) or acetylcholine (30 nM–100 μM). These results have contributed to a structure–activity relationship profile for the P2X1-purinoceptor that will inform future designs of more potent antagonists.

中文翻译：

---

合成 2-苯基-5,6,7,8-四氢喹喔啉衍生物并筛选大鼠输精管分离制剂中的 P2X1-嘌呤受体拮抗剂活性，用于转化为男性避孕药†。

平滑肌细胞在输精管的交感神经介导的收缩是由神经元释放的腺苷5'-三磷酸（ATP）和去甲肾上腺素，这刺激P2X1-嘌呤受体和α介导的_1A -肾上腺素受体，分别。这一过程对于精子运输至关重要，正如在敲除小鼠研究中所证明的那样，P2X1-嘌呤受体和_{α1A 的}同时基因缺失-肾上腺素能受体导致男性不育。我们假设这两种受体的双重药理学拮抗作用可以充分抑制精子运输，从而提供一种新的非激素男性避孕方法。为了产生合适的 P2X1-嘌呤受体拮抗剂，在 2-苯基-5,6,7,8-四氢喹喔啉的苯基部分引入了取代基以产生一系列类似物，这些类似物在大鼠输精管的分离制剂中测试 P2X1-嘌呤受体拮抗作用输精管。最初筛选了新化合物减弱对电场刺激的收缩反应的能力（EFS：60 V、0.5 ms、0.2 Hz）。向间位而非邻位添加极性取代基显着增加了对收缩的抑制，就像在对位添加极性和脂肪族取代基一样。14 μM 中的₅₀个（95% 置信限：12–16 μM）。此外，化合物 31 非竞争性拮抗由外源性给药 αβ-亚甲基 ATP (10 nM–30 μM) 介导的收缩，但对外源性给药的去甲肾上腺素 (30 nM–100 μM) 或乙酰胆碱 (30 nM–100 μM) 介导的收缩没有抑制作用. 这些结果有助于形成 P2X1-嘌呤受体的构效关系，这将为未来设计更有效的拮抗剂提供信息。