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Biol Bull 83: 165-172. (October 1942)
© 1942 Marine Biological Laboratory
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CARDIAC PHARMACOLOGY OF THE CLADOCERAN, DAPHNIA

E. R. BAYLOR 1

1 Department of Zoology, University of Illinois, Urbana

1. Acetylcholine was found to have a depressing effect on the heart rate and strength of beat of the heart of Daphnia magna with the threshold at 10-9 and a depression of 25 per cent at 10-5 The effect is reversible.

2. Atropine has a depressing effect on the heart rate with the threshold at 10-7 and an inhibition of 15 per cent at 10-4 The effect is not reversible.

3. Eserine with a threshold of 10-9 has a toxic effect on the heart of Daphnia causing irreversible inhibition at any higher concentration.

4. Adrenalin has an accelerating effect at 10-7 when prepared from the crystalline form. Commercial adrenalin solution may actually inhibit due to the reducing agent, NaHSO3, which itself inhibits heart rate in concentrations as low as 10-6.

5. Potassium chloride inhibits the heart rate with a threshold at 0.005 M, a 12 per cent inhibition at 0.02 M and death at 0.04 M.

6. The above facts would indicate that the heart of Daphnia more closely resembles the vertebrate heart than that of the higher crustacea in its pharmacology.






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Copyright © 1942 by the Marine Biological Laboratory.