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  • Title: Effects of verapamil and manganese on the vasoconstrictor responses to noradrenaline, serotonin and potassium in human and goat cerebral arteries.
    Author: Salaices M, Marin J, Rico ML, Gonzalez C.
    Journal: Biochem Pharmacol; 1983 Sep 15; 32(18):2711-4. PubMed ID: 6626242.
    Abstract:
    The effects of verapamil and manganese (Mn2+) on the noradrenaline (NA), serotonin (5-HT) and potassium (K+)-induced contractions were studied in human and goat cerebral arteries. Verapamil and Mn2+ relaxed both kinds of cerebral vessels previously contracted with 10(-5) M NA, 10(-5) M 5-HT and 75 mM K+. The ID50 (50% inhibition of maximum contraction) was around 10(-7) M for the organic antagonist and 10(-3) M for the inorganic one. The ID50 for the Ca2+ antagonists in K+-induced contractions was smaller than that for NA and 5-HT-evoked contractions. Preincubation of segments with verapamil (10(-6) M) or Mn2+ (2 X 10(-3) or 5 X 10(-3) M) caused inhibition of the contractions evoked by the three agents that was greater in the case of K+. The inhibitory effects of verapamil were reversed by adding Ca2+ to the bath. The removal of Ca2+ from the extracellular medium reduced the contractions elicited by the three vasoconstrictor agents in both cerebral blood vessels. This reduction was greater for K+ than for the other two. These results indicate that both cerebral vessels are very susceptible to Ca2+ omission and to Ca2+ entry blockers such as verapamil and Mn2+, which could be of interest to treat cerebral vasospasm.
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