Kinetics of G protein-mediated modulation of the potassium M-current in bullfrog sympathetic neurons.
The inhibition of the voltage-dependent, K+ M-current (IM) following receptor-independent G protein activation with controlled intracellular perfusion of nonhydrolyzable GTP analogs had an exponential time course, with rates hyperbolically dependent on GTP analog concentration, and a limiting value of 0.53 min-1. The inhibitory agonist muscarine caused a concentration-dependent acceleration of the rate of nucleotide-induced inhibition, with a plateau of about 20 min-1 and an exponential time course. In neurons not treated with nucleotide analogs the IM recovery rate following agonist removal was 3-7 min-1. It is proposed that the overall kinetics of the transduction pathway for IM modulation is governed by the agonist-dependent kinetics of nucleotide interaction with G proteins. A simple model of IM modulation based on G proteins' kinetics has been developed. These data suggest a possible cellular process responsible for the time course of slow synaptic potentials caused by IM inhibition in sympathetic neurons.
Lopez
H S
HS
Howard Hughes Medical Institute, Department of Neurobiology and Behavior, SUNY, Stony Brook, New York 11794.
D000818:Animals; D004553:Electric Conductivity; D019204:GTP-Binding Proteins / Q000502:physiology*; D005728:Ganglia, Sympathetic / Q000502:physiology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D015640:Ion Channel Gating; D007700:Kinetics; D008564:Membrane Potentials; D009116:Muscarine / Q000494:pharmacology; D009474:Neurons / Q000502:physiology; D011188:Potassium / Q000502:physiology*; D011892:Rana catesbeiana; D011976:Receptors, Muscarinic / Q000502:physiology; D015398:Signal Transduction
D011976:Receptors, Muscarinic; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D009116:Muscarine; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D011188:Potassium