IDENTIFICATION OF M-CHANNELS IN OUTSIDE-OUT PATCHES EXCISED FROM SYMPATHETIC-GANGLION CELLS

We have identified the species of K+ channel that underlies the neuron al M-current in rat sympathetic ganglion cells. The channels were kine tically and pharmacologically defined using outside-out and cell-attac hed patches. They exhibited multiple conductance levels, predominantly 3-9 pS. Their slow gating in response to voltage change in outside-ou t patches was exhibited only in the presence of AlF4- or GTPgammaS on the inner membrane surface and when the lower conductance states were dominant. In the absence of AlF4- or GTPgammaS, the channels exhibited rapid activation and deactivation. We conclude that M-channel gating may be controlled by an associated GTP-binding protein.