Article date: April 1983
By: JM Arnold, DG McDevitt, in Volume 15, Issue 4, pages 423-429
1 Eight healthy subjects (six male, two female, aged 18‐21 years) received graded intravenous bolus injections of isoprenaline sulphate. Heart rate and intra‐arterial blood pressure were continuously monitored PRE‐ and POST‐atropine (0.04 mg/kg). 2 PRE‐atropine, an increase in heart rate of 25 beats/min was produced by 2.15 +/‐ 0.53 micrograms of isoprenaline and was associated with a fall in mean, systolic and diastolic pressures (18.9 +/‐ 2.8, 17.7 +/‐ 3.4 and 20.4 +/‐ 2.3 mm Hg respectively). 3 POST‐atropine, the heart rate dose response curve was shifted to the right so that the dose of isoprenaline which increased heart rate 25 beats/min PRE‐atropine, produced a significantly smaller heart rate rise of 20.3 +/‐ 1.7 beats/min (P less than 0.001). This was associated with a shift of the blood pressure dose‐response curves to the left, and larger falls in mean, systolic and diastolic pressures (30.9 +/‐ 2.8, 31.8 +/‐ 3.3, 30.1 +/‐ 3.3 mm Hg respectively; P less than 0.01). 4 It is concluded that there is a significant contribution from a reflex withdrawal of cardiac vagal tone, to the tachycardia produced by a bolus of isoprenaline.
DOI: 10.1111/j.1365-2125.1983.tb01525.x
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