Modulation of M-channel conductance by adenosine 5' triphosphate in bullfrog sympathetic B-neurones.
1. Adenosine 5' triphosphate (ATP) (0.5-500 microM) or muscarine (0.1-1.0 microM) suppressed M-current/conductance (IM/gM) in B-cells of bullfrog sympathetic ganglion. Both agonists suppressed steady-state M-conductance (gM) at -30 mV and there was either no change or a slight increase in the time constants for gM activation (tau(a) at -30 mV) and deactivation (tau(d) at -50 mV). 2. It has previously been shown that experimental elevation of intracellular Ca2+ concentration ([Ca2+]i) suppresses gM and this is associated with decreases in both tau(a) and tau(d). As these changes in kinetics differ from those we observe with agonist application, our results cast doubt on the hypothesis that elevation of [Ca2+]i is involved in the transduction mechanism for ATP- or muscarine-induced gM suppression.
Chen
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H
National Research Institute of Chinese Medicine, Pei-Tou, Taipei 122, Taiwan, ROC.
Kurennyi
D E
DE
Smith
P A
PA
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001402:B-Lymphocytes; D002118:Calcium / Q000502:physiology; D004553:Electric Conductivity; D005260:Female; D005728:Ganglia, Sympathetic / Q000502:physiology; D007700:Kinetics; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009116:Muscarine / Q000494:pharmacology*; D018721:Muscarinic Agonists / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism; D011892:Rana catesbeiana
D018721:Muscarinic Agonists; D015221:Potassium Channels; D009116:Muscarine; D000255:Adenosine Triphosphate; D002118:Calcium