Journal of Neurophysiology, Vol 72, Issue 2 1010-1019, Copyright © 1994 by APS

ARTICLES

Voltage-activated potassium currents in isolated motor neurons from the jellyfish Polyorchis penicillatus

J. Przysiezniak and A. N. Spencer
Department of Zoology, University of Alberta, Edmonton, Canada.

1. We describe two voltage-activated potassium currents in the swim motor neurons (SMNs) of the hydrozoan jellyfish, Polyorchis penicillatus. Recordings from neurons isolated in primary cultures were made using the tight-seal, whole-cell technique. 2. One current, IK-fast, turned on rapidly (time to peak = 6-15 ms), was half-activated at -10 to 0 mV, decayed with two exponential phases (tau were approximately 70 ms and approximately 1 s), and was half-inactivated by prepulses around -53 mV. It likely plays an important role in regulating the duration of SMN action potentials. IK-fast has features shared by delayed rectifiers and A-like currents in other invertebrates and vertebrates. 3. Another current, IK-slow, elicited from a holding potential of -30 mV, exhibited a slow onset (tau = 65-250 ms), was half-activated approximately +24 mV, exhibited a shallower voltage dependence than IK-fast, and did not inactivate. It was slower than most known delayed rectifiers.

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