Antagonism of tetrodotoxin‐ and procaine‐induced axonal blockade by adenine nucleotides in the frog sciatic nerve

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Abstract
1 The effects of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine on compound action potentials were investigated in de-sheathed frog-sciatic nerve preparations. 2 ATP and ADP but not adenosine antagonized the inhibitory action of tetrodotoxin (TTX) on nerve conduction. AMP had little or no antagonistic effect on TTX-induced axonal block. ATP was more effective than ADP. The effects of the nucleotides were related to the degree of the TTX-induced inhibition and were more evident where the blockade was more intense. 3 ATP and ADP but not adenosine antagonized the procaine-induced axonal blockade which, in some experiments, was completely reversed by these nucleotides. ATP and ADP were of similar potency. 4 The axonal blockade induced by pentobarbitone was not antagonized by ATP, ADP, AMP or adenosine. 5 The possibility that ATP stimulates a TTX-sensitive sodium channel is discussed.