Patch-clamp recording of cAMP-induced membrane current noise in Helix pomatia neurons.

Membrane current noise evoked by intracellular cAMP injection was studied in isolated Helix pomatia neurons with the patch-clamp technique. Fluctuation analysis was used to estimate the elementary current amplitude (i) and the single channel conductance. It was found that i decreased linearly with cell depolarization and the extrapolated reversal potential was approximately -12 mV. The calculated single-channel conductance was 0.9 +/- 0.14 pS, a value quite different from those obtained for cAMP-activated channels in Pleurobranchaea neurons.