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Cardiovascular pharmacology of quazodine (MJ‐1988), with particular reference to effects on myocardial blood flow and metabolic heat production
Author(s) -
PARRATT J. R.,
WINSLOW EILEEN
Publication year - 1971
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1971.tb07100.x
Subject(s) - blood pressure , medicine , cardiac output , heart rate , contractility , diastole , vascular resistance , hemodynamics , cardiology , blood flow , ventricular pressure , isoprenaline , vasodilation , cardiac index , stimulation
Summary1 The effects of intravenous infusions of quazodine (6,7‐dimethoxy‐4‐ethyl‐quinazoline; MJ‐1988) on myocardial blood flow, myocardial metabolic heat production and on general haemodynamics have been studied in cats anaesthetized with sodium pentobarbitone. 2 Quazodine (0·25 and 0·5 (mg/kg)/min for 10 min) decreased diastolic blood pressure, peripheral vascular resistance, systolic ejection time and left ventricular end‐diastolic pressure. Heart rate, cardiac effort, output and external work and left ventricular dP/dt were markedly increased. These changes are indicative of increased myocardial contractility and peripheral vasodilatation. 3 In a dose of (1·0 mg/kg)/min, quazodine had a more marked hypotensive effect, systolic pressure being significantly reduced, and had less effect on left ventricular dP/dt and cardiac effort. Calculated external cardiac work was slightly reduced and there were very occasional nodal arrhythmias. 4 Changes in heart rate, aortic dP/dt and diastolic blood pressure induced by quazodine were unaffected by the previous administration of the β‐adrenoceptor blocking agent alprenolol in a dose (1·0 mg/kg) which abolished the effects of isoprenaline. 5 In all doses, quazodine markedly increased local blood flow (by 70–540%) around an implanted myocardial heated thermocouple recorder. ‘Corrected temperature’, an index of local myocardial metabolic heat production, was almost unchanged and it is suggested that increased myocardial contractility, occurring with unchanged metabolic heat production and oxygen consumption, probably results from a concomitant decrease in intramural wall tension.