Regulation of two ion channels by a common muscarinic receptor-transduction system in a vertebrate neuron.
In bullfrog sympathetic ganglion cells, muscarine produced an inward current (Imus) through the activation of a subtype (M1) of muscarinic acetylcholine receptor (mAChR) by suppressing an outward M-current (IM), and/or activating cation-selective current (ID; see below). The former was induced with a potency (Kd = 0.5 microM) higher than the latter (Kd = 5 microM) before and after blocking a fraction of the receptor with an irreversible blocker. Activators of protein kinase C mimicked muscarine's actions. Blocking IM by Ba2+ increased ID. These results suggest that activation of M1-mAChR both closes M-channel and opens cation-selective D-channel through phosphoinositide breakdown and the subsequent activation of protein kinase C and that a difference in potency at the last step of the cascade determines the order in which channels are regulated.
D000818:Animals; D001464:Barium / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000502:physiology*; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D009116:Muscarine / Q000494:pharmacology; D009474:Neurons / Q000502:physiology*; D011892:Rana catesbeiana; D011976:Receptors, Muscarinic / Q000502:physiology*
D007473:Ion Channels; D011976:Receptors, Muscarinic; D001464:Barium; D009116:Muscarine