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Alpha 1-adrenoceptor-mediated contraction of rabbit mesenteric artery: a role for intra- and extracellular calcium pools



Alpha 1-adrenoceptor-mediated contraction of rabbit mesenteric artery: a role for intra- and extracellular calcium pools



Journal of Cardiovascular Pharmacology 9(4): 401-406



The alpha-adrenoceptors that mediate contraction to exogenous and endogenous noradrenaline in rabbit isolated mesenteric artery were investigated. Prazosin (10(-9)-10(-7) M) antagonised contractions to noradrenaline, methoxamine, and, in particular, contractions to neuronal noradrenaline released by field stimulation. Only a high concentration (10(-5) M) of idazoxan was able to markedly antagonise the three contractile stimuli. The effects of idazoxan (at high concentrations) and prazosin were studied upon noradrenaline-evoked contractions attributable to intracellular Ca2+ release using Ca2+ -deplete medium, and, on readministration of Ca2+, upon Ca2+ influx. Both components of the response were inhibited by the two antagonists, but the contraction associated with intracellular Ca2+ release was preferentially inhibited in each case. The results demonstrate that only alpha 1-adrenoceptors are involved in the contraction of this tissue to exogenous and endogenous noradrenaline. This receptor type is linked to both extracellular and intracellular Ca2+ sources, although the latter is more sensitive to inhibition by alpha-adrenoceptor blocking drugs.

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Accession: 039217787

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PMID: 2438502


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