Sato M, Muramatsu I, Fujiwara M
Blood Vessels. 1984;21(5):246-51. doi: 10.1159/000158517.
Post- and presynaptic alpha-adrenoceptors in the canine mesenteric artery show distinct features of alpha 1 and alpha 2 types, respectively. The effects of a newly synthesized pressor agent, 2-[(5-chloro-2-methoxyphenyl)azo]-1H-imidazole (M6434), on the pre- and postsynaptic alpha-adrenoceptors of the canine mesenteric artery were examined pharmacologically. M6434 produced a contractile response in the mesenteric artery. The EC50 value of M6434 was 1.1 X 10(-7) M, that was almost the same as that of norepinephrine but significantly lower than the value seen with methoxamine. The maximum amplitude of contraction developed by M6434 was approximately 81% of that induced by norepinephrine. The contractile response to M6434 was competitively inhibited by prazosin (pA2 = 9.23 +/- 0.08) and yohimbine (pA2 = 7.85 +/- 0.09). M6434 also reduced the 3H-efflux evoked by electrical transmural stimulation in the arterial tissues preincubated with 3H-norepinephrine, and the maximum inhibition corresponded to about 60% of the case of norepinephrine. This presynaptic effect was inhibited by yohimbine but not by prazosin. The results show that M6434 is almost a full agonist for alpha 1-adrenoceptor with partial alpha 2-effect.
犬肠系膜动脉的突触后和突触前α-肾上腺素能受体分别表现出α1和α2型的不同特征。对一种新合成的升压剂2-[(5-氯-2-甲氧基苯基)偶氮]-1H-咪唑（M6434）对犬肠系膜动脉突触前和突触后α-肾上腺素能受体的作用进行了药理学研究。M6434在肠系膜动脉中产生收缩反应。M6434的EC50值为1.1×10^(-7)M，几乎与去甲肾上腺素相同，但显著低于甲氧明的值。M6434产生的最大收缩幅度约为去甲肾上腺素诱导幅度的81%。对M6434的收缩反应被哌唑嗪（pA2 = 9.23±0.08）和育亨宾（pA2 = 7.85±0.09）竞争性抑制。M6434还减少了在预先用3H-去甲肾上腺素孵育的动脉组织中电透壁刺激诱发的3H外流，最大抑制约相当于去甲肾上腺素情况的60%。这种突触前效应被育亨宾抑制，但不被哌唑嗪抑制。结果表明，M6434几乎是α1-肾上腺素能受体的完全激动剂，具有部分α2效应。
