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Vasoconstriction mediated by postsynaptic α2-adrenoceptor stimulation

  • P. B. M. W. M. Timmermans
  • P. A. van Zwieten
Article

Summary

The postsynaptic α-adrenoceptors involved in vasoconstriction brought about by B-HT 933 (2-amino-6-ethyl-4,5,7,8-tetrahydro-6H-oxazolo-[5,4-d]-azepin) administered i.v. to pithed, normotensive rats were characterized. The rate of onset of the hypertensive response to i.v. B-HT 933 is slower than that induced by (−)-phenylephrine, an agonist of α1-adrenoceptor. The antagonism of the α-adrenoceptor blocking drugs rauwolscine, yohimbine and corynanthine was quantified towards B-HT 933-induced increases in diastolic pressure. Rauwolscine (pA2=7.06) and yohimbine (pA2=6.83) were effective antagonists, whereas corynanthine proved much less potent (pA2=5.03). On the basis of the reported selectivity of yohimbine and its two diastereoisomers rauwolscine and corynanthine for α1- and α2-adrenoceptor, it is concluded that the postsynaptic α-adrenoceptors triggered by B-HT 933 are of the α2-type. B-HT 933 identifies a subclass of postsynaptic α2-adrenoceptor in vascular smooth muscle distinct from postsynaptic α1-adrenoceptor. Both types of α-adrenoceptors are likely to be involved in the mediation of vasoconstriction.

Key words

B-HT 933 Yohimbine diastereoisomers Vasoconstriction Postsynaptic α2-adrenoceptor 

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Copyright information

© Springer-Verlag 1980

Authors and Affiliations

  • P. B. M. W. M. Timmermans
    • 1
  • P. A. van Zwieten
    • 1
  1. 1.Department of Pharmacy, Division of PharmacotherapyUniversity of AmsterdamAmsterdamThe Netherlands

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