The effects of histamine on cardiovascular system in 6 dogs were analyzed. Mongrel dogs, 10 to 16 kg in body weight, were anesthetized with Nembutal (30 mg/kg) and arterial blood pressure, heart rate, central venous pressure, electrocardiogram were recorded and measured plasma potassium concentration. Histamine (100μg/ml) was infused slowly at the rate of 0.25 ml/min through the external jugular vein until BP was 80/60 and maintained restored BP for more than 5 min. The process repeated 4 ~ 5 times. At each time before and after infusion every items were recorded and measured. 1. Arterial blood pressure was 142/105 (mean 117) mmHg in control and decreased to 90/60 68) after histamine infusion. 2. Heart rate changed from 175 beat/min to 150 and central venous pressure from 6.2 to 5.2 cm H<sub>2</sub>O. 3. Plasma potassium concentration was 4.3 mEq/L and slightly increased to 4.7 mEq/L but it was not significant statistically. 4. Most characteristic changes revealed in EKG especially in T-waves. Height, Width, Steepness, and Slimness were increased 1.5 ~ 3.7 times than control level and Pointedness decresed 0.5 times than before.
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