Activation of ATP-sensitive K channels by a K channel opener (SR 44866) and the effect upon electrical and mechanical activity of frog skeletal muscle.
To examine the effects of the activation of adenosine 5'-triphosphate (ATP)-sensitive K channels in a skeletal muscle we have applied the ATP-sensitive K channel opener SR44866 whilst recording single ion channels, voltage-clamped membrane currents, evoked action potentials and tension in sartorius muscles of the frog. In excised inside-out membrane patches SR44866 opened channels which could be inhibited by internal ATP and glibenclamide. In voltage-clamped individual muscle fibres SR44866 evoked a glibenclamide-sensitive membrane current which reversed at -70 mV. The effect of SR44866 was dose dependent with an effective concentration for 50% maximal effect (EC50) of 67 microM and a slope factor of 2. SR44866 dose dependently reduced the duration of the spike after-potential, spike overshoot, Vmax, tetrodotoxin-sensitive voltage-gated inward membrane currents and muscle twitch tension. From this evidence it can be concluded that the opening of ATP-sensitive K channels may be associated with the inhibition of contraction of skeletal muscle.
Sauviat
M P
MP
Laboratoire de Physiologie Comparée (URA CNRS 1121), Orsay, France.
Ecault
E
E
Faivre
J F
JF
Findlay
I
I
D000200:Action Potentials / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001578:Benzopyrans / Q000008:administration & dosage / Q000494:pharmacology*; D002462:Cell Membrane / Q000502:physiology; D004095:Dihydropyridines / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011893:Rana esculenta; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D001578:Benzopyrans; D004095:Dihydropyridines; D015221:Potassium Channels; D015222:Sodium Channels; D013779:Tetrodotoxin; C061050:bimakalim; D000255:Adenosine Triphosphate; D005905:Glyburide