Forskolin but not isoprenaline increases sodium current from frog cardiac myocytes.

The effect of forskolin on sodium current (INa) was studied in enzymatically dispersed frog atrial myocytes. The single pipette patch-clamp technique was used, with a low external sodium concentration. Forskolin (0.5 microM) increased INa at all potentials between -50 and +30 mV. The forskolin-induced increase of INa was mimicked by 1,9-dideoxyforskolin (0.5 microM) but not by isoprenaline (2 microM). These results suggest that forskolin can modulate INa through a mechanism that does not involve the production of cyclic AMP.