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Journal of Neuroscience, Vol 12, 2065-2078, Copyright © 1992 by Society for Neuroscience

ARTICLE

Voltage-activated calcium currents in identified neurons from a hydrozoan jellyfish, Polyorchis penicillatus

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

Calcium currents were studied in isolated "swim motor neurons" from the jellyfish Polyorchis penicillatus, using the tight-seal, whole-cell, voltage-clamp technique. Two high-voltage-activated (HVA) currents were observed. The transient current, HVA-t, activated rapidly (time to peak, 4 msec), inactivated with two time constants (26 msec, 187 msec) in a positive voltage range (Vi = -23 mV), and was larger when carried by calcium than by barium ions. The sustained current, HVA-s, inactivated slowly or not at all, even at very positive voltages and had the same amplitude whether carried by Ca2+ or Ba2+. It is likely that the two HVA current components arise from distinct channel populations, because the ionic selectivity of calcium channels is not known to depend on their inactivation kinetics. A third current appeared to activate at very positive voltages, and at a slower rate than did HVA-t. It is likely to be an artifact of inhomogeneous space clamping. A low-voltage-activated, cadmium-insensitive calcium current may also be present. Calcium currents in this primitive, multicellular animal have properties similar to calcium currents in other phyla; however, they do not fit neatly into the "T, N, L" classification scheme of vertebrate calcium currents.

This article has been cited by other articles:

				Y.-C. J. Lin and A. N. Spencer Calcium currents from jellyfish striated muscle cells: preservation of phenotype, characterisation of currents and channel localisation J. Exp. Biol., January 11, 2001; 204(21): 3717 - 3726. [Abstract] [Full Text] [PDF]

				M. C. Jeziorski, R. M. Greenberg, K. S. Clark, and P. A. V. Anderson Cloning and Functional Expression of a Voltage-gated Calcium Channel alpha 1 Subunit from Jellyfish J. Biol. Chem., August 28, 1998; 273(35): 22792 - 22799. [Abstract] [Full Text] [PDF]

				T. Jegla and L. Salkoff A Novel Subunit for Shal K+ Channels Radically Alters Activation and Inactivation J. Neurosci., January 1, 1997; 17(1): 32 - 44. [Abstract] [Full Text] [PDF]

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