Summary
In the anesthetized cat phenylephrine in doses of 10−8, 3 × 10−8 and 10−7 moles/kg caused an increase of dp/dtmax. of the left ventricle without altering the heart rate. This cardiostimulating effect was inhibited by the α-adrenolytic drug phentolamine (10−6 moles/kg). The ß-adrenolytic agent prindolol (10−7 moles/kg), which inhibited the increase of dp/dtmax evoked by isoprenaline as well as by noradrenaline did not influence the positive inotropic effect of phenylephrine, thus favouring the view that there exist myocardial α-adrenoceptors in the ventricle of the cat.
Zusammenfassung
An der narkotisierten Katze verursacht Phenylephrin in Dosen von 10−8, 3 × 10−8 und 10−7 Mol/kg einen Anstieg von dp/dtmax des linken Ventrikels, ohne dabei die Schlagfrequenz zu ändern. Die kardiostimulierende Wirkung des Phenylephrins wurde durch das α-Adrenolytikum Phentolamin (10−6 Mol/kg) gehemmt. Das ß-Adrenolytikum Prindolol (10−7 Mol/kg), das den durch Isoprenalin und Noradrenalin verursachten Anstieg von dp/dtmax hemmte, war ohne Wirkung gegenüber der positiv inotropen Wirkung des Phenylephrins. Diese Untersuchungen stützen die Auffassung, daß im Ventrikel der Katze myokardiale α-Adrenozeptoren vorkommen.
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This work was supported by the Deutsche Forschungsgemeinschaft and a grant from Deutscher Akademischer Austauschdienst to E.R.P., Dept. of Pharmacology, University of Porto, Portugal.
The authors wish to thank Mrs. GAbriele GRAF for skilful technical assistance.
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Rodrigues-Pereira, E., Wagner, J. Stimulation by phenylephrine of myocardial alpha-adrenoceptors in the left ventricle of the cat. Res. Exp. Med. 166, 165–171 (1975). https://doi.org/10.1007/BF01851182
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DOI: https://doi.org/10.1007/BF01851182