Antagonism of alpha1-adrenoceptor agonist-induced responses by rilmenidine in vascular smooth muscle

European Journal of Pharmacology
C Cario-ToumaniantzP Pacaud

Abstract

The effect of the centrally acting antihypertensive agent, rilmenidine, was examined on the contractile properties of isolated rat portal vein strips and on the free cytosolic [Ca2+] ([Ca2+]i) in isolated myocytes. Rilmenidine (1-30 microM) relaxed strips precontracted with noradrenaline. This effect was not inhibited by the alpha2-adrenoceptor antagonist, yohimbine, and was not mimicked by the alpha2-adrenoceptor agonist, 5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine (UK 14,304). Rilmenidine dose dependently shifted to the right the concentration-response curves to noradrenaline and to phenylephrine but not that to carbachol. Rilmenidine alone (0.1-30 microM) caused a contraction which maximally corresponded to 18% of the maximal noradrenaline-induced contraction. This effect was not produced by UK 14,304, was not affected by yohimbine, but was inhibited by the alpha1-adrenoceptor antagonist, prazosin. In isolated myocytes, rilmenidine reduced the noradrenaline-induced [Ca2+]i increase but alone, it produced a rise in [Ca2+]i, the peak amplitude of which averaged 15% of the noradrenaline-induced transient [Ca2+]i rise. It is concluded that rilmenidine acts as a partial agonist of alpha1-adrenoceptors of vascular s...Continue Reading

References

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Jan 1, 1994·Journal of Cardiovascular Pharmacology·F Sannajust, G A Head
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