CONTROL OF M-CURRENT

M-current is a non-inactivating potassium current found in many neuron al cell types. In each cell type, it is dominant in controlling membra ne excitability by being the only sustained current in the range of ac tion potential initiation. It can be modulated by a large array of rec eptor types, and the modulation can occur either by suppression or enh ancement. Modulation of M-current has dramatic effects on neuronal exc itability. This review discusses the numerous second messenger pathway s that converge on regulation of this current: in particular, two form s of regulation of the M-current, receptor-mediated modulation and the control of macroscopic current amplitude by intracellular calcium. Bo th types of regulation are discussed with reference to the modulation of single-channel gating properties.