Calcium and sodium ions as charge carriers in the action potential of an identified snail neurone.
1. The soma of cell A in Helix aspersa produced action potentials in sodium-free or calcium-free saline, but not in saline with neither sodium nor calcium. 2. The axon had a sodium-dependent action potential. 3. Tetrodotoxin (5 x 10(-6) M) had no effect on the overshoot except at low external divalent ion concentrations. 4. The action potential in sodium-free saline was blocked by cobalt. 5. The slope of action potential overshoot against sodium concentration in the presence of 10 mM calcium was 10.5 mV/tenfold change. That of overshoot against calcium concentration in the presence of 75 mM sodium was 22 mV/tenfold change. 6. In sodium-free saline the slope of overshoot versus calcium concentration was 27 mV/tenfold change. 7. It is concluded that calcium is an important charge carrier in the action potential of cell A.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001369:Axons / Q000502:physiology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D003035:Cobalt / Q000494:pharmacology; D006372:Helix, Snails; D066298:In Vitro Techniques; D009474:Neurons / Q000502:physiology*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology
D003035:Cobalt; D013779:Tetrodotoxin; D012964:Sodium; D002118:Calcium