Ionic channels in the node of Ranvier are not modulated by cyclic adenosine monophosphate.

The effect of a cyclic adenosine monophosphate (cAMP) analogue on myelinated axons was studied. The lipophilic dibutyryl cAMP (dbcAMP) was applied to isolated frog axons under voltage clamp conditions. No effect on the ionic currents was observed for either external or internal application of dbcAMP. Nor was any effect of the phosphodiesterase inhibitor theophylline found. These results suggest that cAMP does not play an essential role for nerve impulse conduction in axons. This conclusion deviates from those of other studies.