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Journal of Experimental Biology 154,45-65 (1990)
Published by Company of Biologists 1990

Characteristics of Five Types of K+ Channel in Cultured Locust Muscle

1 and P. N. Usherwood 1

1 Department of Zoology, University of Nottingham University Park, Nottingham NG7 2RD, UK

K+ channel activity in cultured locust myofibres was investigated using gigaohm patch-clamp techniques. After 2 months in vitro the myofibres had a mean resting potential of -39 ± 7 mV (±S.D., 7V = 42). Five types of K+ channel were identified at this time. The majority of single-channel events recorded from cellattached patches were due to a small-conductance (type 1) and a largeconductance (type 2), inward rectifier, K+ channel. In cell-attached patches, with 180 mmoll-1 KC1 in the patch pipette, the type 1 channel had a chord conductance of 43 pS for inward currents and 8pS for outward currents; the type 2 channel had a chord conductance of 115 pS for inward currents and 29 pS for outward currents. The type 2 channel exhibited bursting kinetics, was ATP-sensitive and could be blocked by Ba2+. Two other channels (types 3 and 4) had linear conductances of 130pS and 207pS, respectively. The type 3 channel was Ca2+-sensitive. A further channel (type 5) appeared to be an inward rectifier with a conductance of 5pS. Openings of types 3, 4 and 5 channels occurred less frequently than openings of the other two channels. Types 1, 2, 3 and 4 channels possessed multiple closed and open states with non-linear gating mechanisms.

Key words: cultured muscle, K+ channel, patch-clamp, Schistocerca gregaria

Accepted on July 3, 1990






© The Company of Biologists Ltd 1990