Effects of verapamil and manganese on the vasoconstrictor responses to noradrenaline, serotonin and potassium in human and goat cerebral arteries.
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.
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D005260:Female; D006041:Goats; D008345:Manganese / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology*; D014661:Vasoconstriction / Q000187:drug effects*; D014700:Verapamil / Q000494:pharmacology*
D012701:Serotonin; D008345:Manganese; D014700:Verapamil; D011188:Potassium; D009638:Norepinephrine