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  • Title: Effects of 2-[(5-chloro-2-methoxyphenyl)azo]-1H-imidazole (M6434), a new alpha-adrenoceptor agonist, on pre- and postsynaptic alpha-adrenoceptors in canine mesenteric artery.
    Author: Sato M, Muramatsu I, Fujiwara M.
    Journal: Blood Vessels; 1984; 21(5):246-51. PubMed ID: 6087962.
    Abstract:
    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.
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