Cyclic GTP imitates the potentiating effect of the nootrope vinpocetine on the high-threshold A-current in mollusk neurons.

Isolated common snail neurons were studied using two-microelectrode potential clamping to record high-threshold (threshold = 10 mV) rapidly-inactivating potassium current (I(Aht)); the effects of the nootrope vinpocetine on this current were studied and were compared with the effects of cyclic nucleotides. Intracellular application of dibutyryl derivatives of cyclic adenosine monophosphate (dcAMP) and guanosine monophosphate (dcGMP) was used. The results showed that vinpocetine potentiates or fails to alter I(Aht) in different cells, while dcGMP imitates the effect of vinpocetine.

Nootropic agent vinpocetine blocks delayed rectified potassium currents more strongly than high-threshold calcium currents.

A two-microelectrode potential clamping method was used on isolated common snail neurons to measure high-threshold Ca2+ and delayed rectified K+ currents. Addition of the nootropic agent vinpocetine (VPC) to the bathing solution rapidly and reversibly inhibited both types of current. The effects of VPC were dose-dependent and were independent of the test stimulus voltage.