Capsaicin blocks one class of K+ channels in the frog node of Ranvier.

Capsaicin (10-20 microM) blocks reversibly one component of the K+ current (IKf2) in frog node of Ranvier. The block is enhanced with depolarization but it is not voltage-dependent indicating that the affinity of receptor sites for capsaicin is larger with the channels in the open configuration. The results provide pharmacological evidence of the existence within the nodal membrane of two classes of fast K+ channels, in addition to the slow K+ channels.