VOLTAGE CHANGE-INDUCED GATING TRANSITIONS OF THE RABBIT SKELETAL-MUSCLE CA2+ RELEASE CHANNEL

1. We used the planar lipid bilayer method to study single ryanodine r eceptor Ca2+ release channels (RyRCs) from fast skeletal muscle of the rabbit. We found that changes in membrane voltage directly induced ga ting transitions of the RyRC: (i) in the steady state, even at activat ing Ca2+ concentrations (20 mu M), at a constant membrane potential th e channels resided in a low open probability (P-o) state (inactivated- , I-mode), and (ii) upon abrupt changes of voltage, the apparent inact ivation of the RyRCs was relieved, resulting in a rapid and transient increase in P-o. 2. The magnitude of the P-o increase was a function o f both the duration and the amplitude of the applied prepulse, but was independent of the channel activity during the prepulse. 3. The volta ge-induced P-o increase probably insolved major conformational changes of the channel, as it resulted in substantial alterations in the gati ng pattern of the channels: the voltage change-induced increase in P-o was accompanied by the rapid appearance of two types of channel activ ity (high (H) and low (L) open probability modes). 4. The response of the RyRC to voltage changes raises the interesting possibility that th e activation of RyRC in situ, might involve electrical events, i.e. a possible dipole-dipole coupling between the release channel and the vo ltage sensor.