The Ionic Basis of the Fast Action Potentials in the Isolated Cerebro-visceral Connective of Anodonta Cygnea

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Abstract
1. The large axons in the cerebro-visceral connective have been shown to function for appreciable periods in preparations bathed in sodium-free non-electrolyte solutions. 2. The results of experiments on the effects of organic monovalent cations and anions, together with observations on the effects of tetrodotoxin, procaine and manganous ions and the changes in conduction velocity in tris chloride and dextran solutions indicate that the action potentials are, nevertheless, mediated by conventional sodium-dependent mechanisms. 3. Radioisotope experiments show that there is a small fraction, of approx. 0.5 mM/kg. tissue, which does not exchange rapidly with the 22Na in the bathing medium and which can be depleted by stimulation in sodium-free solutions. 4. On the basis of these observations it is suggested that there is sequestered extra-axonal sodium fraction which can be utilized by the large axons to maintain action potentials in preparations bathed in sodium-free solutions.