MUSCARINIC REGULATION OF MEMBRANE ION CHANNELS IN AIRWAY SMOOTH-MUSCLE CELLS

We have demonstrated that stimulation of airway smooth muscle by muscarinic agonists results in a coordinated modulation of two membrane ion channel proteins. Both channels are modulated in a similar way, although their effects on open-channel probability are opposite. The voltage-dependence of channel activity is shifted to more positive potentials in the case of K(Ca), and to more negative potentials in the case of the voltage-dependent calcium channels. Similarly, K(Ca) channel dwell-time kinetics are shifted to short open lifetimes, whereas the long open state is favored for the large-amplitude voltage-dependent calcium channel. Although little is known about the molecular coupling of calcium channels, muscarinic inhibition of K(Ca) channels is mediated through a pertussis toxin-sensitive guanine nucleotide binding protein.