Modulation of cyclic nucleotide levels in peripheral nerve without effect on resting or compound action potentials.

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Abstract
Cyclic nucleotide levels and compound action potential magnitudes were measured in frog [Rana pipiens] sciatic nerves following exposure to carbachol, isoprenaline and cyclic nucleotide related substances. The resting cyclic(c)AMP level was 2.4 pmol/mg protein and the cGMP level was 0.27 pmol/mg protein in desheathed nerves. Isoprenaline (100 .mu.M) caused a 2-fold increase in cAMP without affecting cGMP levels. Carbachol (100 .mu.M) caused a 2-fold increase in cGMP without affecting cAMP levels. The phosphodiesterase inhibitor theophylline (5 mM) augmented both cAMP and cGMP. The magnitude of the resting or compound action potential was not affected by isoprenaline, carbachol or phosphodiesterase inhibitors. The cyclic nucleotides and their butyryl derivatives did not affect the magnitude of the resting or compound action potential, either when applied alone or in the presence of a phosphodiesterase inhibitor. In contrast to synaptic tissue, hormone mediated cyclic nucleotide metabolism in peripheral nerve is apparently unrelated to the control of axonal excitability.