STUDIES OF CITRUS AURANTIUM AND ITS HYPERTENSIVE INGREDIENTS ON THE CARDIAC FUNCTIONS AND HEMODYNAMICS IN COMPARISON WITH DOPAMINE AND DOBUTAMINE

In order to elucidate the mechanism of hypertensive and antishock effects of Citrus aurantium L. and its active principles (synephrine and N-methyltyramine), carotid arterial blood pressure (BP), left ventricular pressure (LVP), left ventricular end diastolic pressure (LVEDP), the first derivative of the left ventricular pressure (dp/dt), central venous pressure (CVP), EGG, heart rate (HR), and cardiac output (CO) were monitored in 6 anethetized open chest dogs. The tracings were recorded on RM-86 Polygraph. EGG, LVP, LVEDP and dp/dt signals were recorded simultaneously on Data Recorder and were reproduced in speed of 100 mm per sec. after experiment, so as to measure the numeral value of LVEDP, t-dp/dt, tension time index of ventricular ejection (TTI) and common peak isovolumetric pressure (CPIP). Cardiac index (CI), stroke index (SI), left ventricular work index (LVWI), peripheral vascular resistance (PVR), and dp/dt/CPIP (VcEat CPIP)were calculated. Citus auruntium extract (0.5g/kg), synephrine (1 mg/kg), N-methyltyramine (0.25 mg/kg) with the well-known cardiac stimulants dopamine (DA), dobutamine (DB) as positive control were injected in sequence of Latinsquare design.All drugs markedly increased the cardiac function indices in similar patterns including increase of dp/dt max, V_CE at CPIP and CI; shortening of t-dp/dt max. and lowering of LVEDP. Since V_CE at CPIP is independent of variations of ventricular afterload initiated by these drugs, it was concluded that similar to DA and DB, crude extract of Citrus aurantium and its active principlcs do possess inotropic action by increasing myocardial contractility. It is their pump-stimulant action and elevation of PVR that offer the pharmacological basis to their anti shock effect. As to the relative efficiency on PVR, N-methyltyramine was weaker than crude extract of Citrus aurantium and synephrine. As to the heart rate stimulant action, the reverse was true.At the equivalent dosage to CI increment, crude extract of Citus aurantium synephrine, N-methyltyramine and hypertensive dose of DA augmented the LVWI and TTI×HR (as energy and oxygen consumption index) far beyond the ratio of CI increment. This difference could attribute to the increase of ventricular afterload as a result of vasoconstriction.DB and DA in small doses lowered arterial blood pressure and PVR. Consequently the LVWI and TTI×HR were not significantly altered.