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Alpha-thrombin was applied in cumulative concentrations of 0.001, 0.01, 0.1, 1.0, 10, and/or 100 U/ml to determine peak responses in isolated canine arterial rings. Alpha-thrombin failed to elicit contraction in the mesenteric artery, produced inconsistent effects in the renal artery, and produced biphasic effects (relaxation superseded by contraction) in the coronary and basilar arteries. In the basilar artery the relaxation induced by alpha-thrombin was blocked and the maximal contractions enhanced by reaming the vessel or by substituting heated thrombin for alpha-thrombin. The results support the hypotheses that alpha-thrombin acts on two distinct receptors in the basilar artery and that it is involved in the pathogenesis of cerebral vasospasm.
White et al. (Tue,) studied this question.