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Antagonist properties of phentolamine at both presynaptic α2-adrenoceptors and presynaptic dopamine receptors using field stimulated right cat atria

Authors :
Jay C. Koons
Jan R. Flynn
John P. Long
Source :
European Journal of Pharmacology. 88:311-317
Publication Year :
1983
Publisher :
Elsevier BV, 1983.

Abstract

Phentolamine, which is considered a specific alpha-adrenoceptor antagonist, was tested for antagonist properties at presynaptic dopamine receptors and presynaptic alpha 2-adrenoceptors present on sympathetic nerve terminals in isolated right cat atria. Field stimulation induced a transient tachycardia which was inhibited by stimulation of presynaptic dopamine receptors using apomorphine or by stimulation of presynaptic alpha 2-adrenoceptors using clonidine. The presynaptic inhibitory effects of apomorphine were competitively antagonized by sulpiride, which is considered a specific dopamine receptor antagonist, and by phentolamine and yohimbine which are considered alpha-adrenoceptor antagonists. The presynaptic inhibitory effects of clonidine were competitively antagonized by phentolamine and yohimbine but not by sulpiride. pA2 values for phentolamine against apomorphine and phentolamine against clonidine suggest that phentolamine may be an antagonist at both presynaptic dopamine receptors and presynaptic alpha 2-adrenoceptors.

Details

ISSN :
00142999
Volume :
88
Database :
OpenAIRE
Journal :
European Journal of Pharmacology
Accession number :
edsair.doi.dedup.....dd33116c06108754865858a42282477f
Full Text :
https://doi.org/10.1016/0014-2999(83)90581-2