Pharmacological properties of 2-[(5-chloro-2-methoxyphenyl)azo]-1H-imidazole (M6434)

Pharmacological properties of 2-[(5-chloro-2-methoxyphenyl)azo]-1H-imidazole (M6434) were investigated in vivo and in vitro experiments. M6434 showed a dose-dependent pressor effect in conscious rats at oral doses ranging from 1 to 5 mg/kg. The pressor effect of M6434 was 10 times as potent as those of phenylephrine and methoxamine. M6434 also showed a dose-dependent pressor effect in anesthetized dogs at i.v. doses ranging from 3 to 30 micrograms/kg. The effect of M6434 returned to control level 30 to 45 min after i.v. injection. M6434 caused a contraction of isolated guinea-pig aortic spiral strip at concentrations ranging from 10(-8) to 10(-4) mol/l. pD2 value of M6434 was larger than those of the other sympathomimetics, yet the maximal response of M6434 was 83.4% of the maximal response of noradrenaline. Pretreatment with phentolamine caused a parallel shift of the concentration-response curve of M6434 to the right. However, this effect of M6434 on an isolated aorta was not diminished even in reserpinized guinea-pigs. Therefore, the pressor effect of M6434 may be due to the direct adrenergic alpha-stimulation. M6434 is expected to be effective for the oral treatment of hypotensive disorders.