Selective reduction of one mode of M-channel gating by muscarine in sympathetic neurons.
M-current is widespread in the nervous system. It stabilizes cell excitability, and its suppression by muscarinic receptor activation underlies slow synaptic transmission in sympathetic neurons. Suppression of M-current was one of the first examples of neuromodulation of a potassium current, but the mechanism is not understood. Single-channel recording was used to study this issue. An M-channel with two conductance states, which exhibited appropriate voltage-dependent kinetics with two modes of gating, has been resolved. Mode 1 comprises short open time, low open probability events, and mode 2 openings represent long open time, high open probability behavior. Muscarine decreased M-channel activity by selectively reducing mode 2 M-channel gating through a diffusible second messenger. It is suggested that control of modal gating may be a widespread mechanism for neuromodulation.
Marrion
N V
NV
Department of Neurobiology and Behavior, SUNY, Stony Brook 11794.
D000818:Animals; D004553:Electric Conductivity; D004594:Electrophysiology; D015640:Ion Channel Gating; D009116:Muscarine / Q000494:pharmacology*; D009474:Neurons / Q000502:physiology*; D015221:Potassium Channels / Q000502:physiology*; D011892:Rana catesbeiana; D013564:Sympathetic Nervous System / Q000166:cytology / Q000502:physiology*
D015221:Potassium Channels; D009116:Muscarine