Identification of single transiently opening ("A-type") K channels in guinea-pig colonic myocytes.
Two K+ channel populations were identified in depolarized cell-attached membrane patches of myocytes freshly dispersed from the circular smooth muscle of guinea-pig proximal colon. First, a large-conductance (150 pS) Ca(2+)-activated K+ channel which was non-inactivating and sensitive to blockade by tetraethylammonium (TEA, 0.5-5 mM); and second, a smaller conductance K+ channel which opened and closed within 100 ms, was insensitive to TEA (0.5-5 mM), but was blocked by 5 mM 4-aminopyridine (4-AP) or maintained depolarization, and which had a unitary conductance of 12-13 pS. The averaged time course of these smaller conductance K+ channels closely resembled the time course of the 4-AP-sensitive, Ca(2+)-insensitive transient outward K+ current recorded in the whole-cell recording mode.
Vogalis
F
F
Department of Physiology, Monash University, Clayton, Victoria, Australia.
Lang
R J
RJ
D015761:4-Aminopyridine / Q000037:antagonists & inhibitors*; D000818:Animals; D003106:Colon / Q000502:physiology*; D006168:Guinea Pigs; D008564:Membrane Potentials; D009130:Muscle, Smooth / Q000502:physiology; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000502:physiology*
D015221:Potassium Channels; D015761:4-Aminopyridine