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DOES SUPPRESSION OF RESPONSIVENESS TO β‐ADRENOCEPTOR ACTIVATION EXPLAIN THE ENHANCEMENT OF VASOCONSTRICTOR RESPONSES BY α 2 ‐ADRENOCEPTOR AGONISTS?
Author(s) -
Rand M. J.,
Xiao X.H.,
Rajanayagam S.,
Story D. F.
Publication year - 1989
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1989.tb01587.x
Subject(s) - phenylephrine , propranolol , vasodilation , agonist , vasoconstrictor agents , adrenergic receptor , chemistry , medicine , vasoconstriction , endocrinology , receptor , blood pressure
SUMMARY 1. The α 2 ‐adrenoceptor agonist TL99, in concentrations that had no other observable effect, enhanced constrictor responses to phenylephrine in perfused segments of the rat tail artery. 2. Vasoconstrictor responses to phenylephrine were also enhanced by propranolol (0.3 μmol/L). 3. Vasoconstrictor responses to phenylephrine in the presence of propranolol were further enhanced by TL99 (10 nmol/L). 4. The enhancement of vasoconstrictor responses by α 2 ‐adrenoceptor agonists is not due to the removal of a counteracting vasodilator component produced by activation of p‐adrenoceptors.