Interaction between alpha2-autoreceptors and receptors mediating the effects of angiotensin II and bradykinin in the heart of newborn rats

The interaction between alpha2-autoreceptors and receptors for angiotensin II and bradykinin was studied in the heart of newborn rats. The tissues were labelled with [3H]noradrenaline and then superfused with cocaine-containing medium and stimulated electrically. Angiotensin II (10-300 nM) and brady...

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Published inEuropean journal of pharmacology Vol. 453; no. 2-3; pp. 265 - 270
Main Authors Mota, Alberto, Guimarães, Serafim
Format Journal Article
LanguageEnglish
Published Netherlands 25.10.2002
Subjects
Adrenergic alpha-Antagonists - pharmacology
Alkaloids
Angiotensin II - pharmacology
Animals
Animals, Newborn
Autoreceptors - metabolism
Benzophenanthridines
Bradykinin - pharmacology
Colforsin - pharmacology
Electric Stimulation
In Vitro Techniques
Myocardium - metabolism
Norepinephrine - metabolism
Phenanthridines - pharmacology
Protein Kinase C - antagonists & inhibitors
Rats
Rats, Wistar
Receptors, Angiotensin - physiology
Receptors, Bradykinin - metabolism
Staurosporine - pharmacology
Yohimbine - pharmacology
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Summary:The interaction between alpha2-autoreceptors and receptors for angiotensin II and bradykinin was studied in the heart of newborn rats. The tissues were labelled with [3H]noradrenaline and then superfused with cocaine-containing medium and stimulated electrically. Angiotensin II (10-300 nM) and bradykinin (3-100 nM) enhanced the evoked overflow of tritium, the maximum increase reaching 63.2% and 87.1%, respectively. Blockade of alpha2-adrenoceptors by 100 nM yohimbine reduced, and that by 1 microM abolished, the effect of both angiotensin II and bradykinin. On the contrary, chelerythrine and staurosporine--blockers of protein kinase C--as well as forskolin, an activator of adenylyl cyclase and a blocker of phosphodiesterase, markedly enhanced the facilitatory effect of angiotensin II and bradykinin. We conclude that: (1) alpha2-autoreceptors are present in the heart of newborn rats which interact with prejunctional receptors for angiotensin II and bradykinin also present in the rat heart at that age; (2) the facilitatory influence of chelerythrine and staurosporine on the one hand and that of forskolin on the other hand suggests a link between protein kinase C and cyclicAMP pathways.
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ISSN:0014-2999