Mechanical modulation of a voltage-dependent non-inactivating K+ current in cultured bullfrog sympathetic neurones.
Cultured bullfrog sympathetic ganglion cells were voltage-clamped with a whole-cell patch-clamp technique. Local flow of a solution (identical to the bathing solution) from a micropipette to a cell, but not other mechanical stimuli, produced a non-inactivating outward (in 34 cells out of 141) or inward (in 70 cells) current [I(f)(out) or I(f)(in), respectively] depending on cells. Both I(f)(out) and I(f)(in) appeared at voltages more positive than -60 mV. The mechanism, however, was activated even at -70 mV, as I(f)(out) or I(f)(in) appeared on shifting membrane potential to -30 mV immediately after the local flow. I(f)(out) and I(f)(in) were accompanied by increases and decreases, respectively, in the membrane conductance and current relaxation to a voltage jump between -30 mV and -55 mV without a change in its time constant (whose value was similar to that of a voltage-dependent non-inactivating K+ current, IM), and reversed at a membrane potential close to the equilibrium potential for K+. Both I(f)(out) and I(f)(in) were blocked by Ba2+ (4-8 mM), a blocker of IM, and by muscarine (10 microM), which produced either an "apparent inward" or outward current. A transient outward current activated by a voltage jump from -85 mV (or -75 mV) to -30 mV was little affected by a local flow of a solution which produced I(f)(out) or I(f)(in). These results suggest that the local solution flow produced I(f)(in) or I(f)(out) by deactivating or activating IM, respectively.
Hara
S
S
Department of Physiology, Saga Medical School, Japan.
Kuba
K
K
D000818:Animals; D001464:Barium / Q000494:pharmacology; D005728:Ganglia, Sympathetic / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D017136:Ion Transport / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009116:Muscarine / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010812:Physical Stimulation; D011188:Potassium / Q000378:metabolism*; D011892:Rana catesbeiana
D001464:Barium; D009116:Muscarine; D011188:Potassium