THE EFFECT OF ADRENALIN CHLORIDE AND TOAD VENOM ON THE BLOOD PRESSURE AND HEART RATE OF THE TROPICAL TOAD, BUFO MARINUS

¹ From the Bermuda Biological Station for Research and the Physiological Laboratory of Boston University School of Medicine

1. Adrenalin chloride injected intravenously in Bufo marinus in doses of 0.33 µg. to 2 µg. per 100 grams produced a rise in systolic blood pressure of 21 per cent to 136 per cent. The average minimal effective dose was 0.05 µg. per 100 grams, ranging from 0.02 µg. to 0.09 µg.

2. Doses of 0.33 µg. to 2.5 µg. per 100 grams generally caused a decrease in heart rate of 6 per cent to 67 per cent associated with the rise of blood pressure.

3. Toad venom injected intravenously in Bufo marinus in doses of 4 µg. to 160 µg. per 100 grams produced a rise of systolic blood pressure of 33 per cent to 292 per cent. The average minimal effective dose was 0.5 µg. per 100 grams, ranging from 0.32 µg. to 0.71 µg.

4. The vasoconstrictor mechanism of Bufo marinus is one-tenth as sensitive to its venom as to adrenalin.

5. The response to adrenalin in Bufo marinus suggests the existence of a reflex cardio-inhibitory mechanism stimulated by increased intravascular pressure.

6. No vasodilators are present in Bufo marinus sensitive to adrenalin chloride in doses down to one twenty-fifth of the minimal effective pressor dose.

7. The vasoconstrictor mechanisms of Bufo marinus, of the dog, and of the rat are about equally sensitive to adrenalin.