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Membrane currents in small cultured rat hippocampal neurons: a voltage‐clamp study.
Author(s) -
Johansson S,
Arhem P
Publication year - 1992
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1992.sp018916
Subject(s) - reversal potential , membrane potential , tetrodotoxin , pipette , chemistry , voltage clamp , biophysics , cardiac transient outward potassium current , patch clamp , current (fluid) , transient (computer programming) , electrophysiology , ion , neuroscience , biochemistry , biology , physics , thermodynamics , organic chemistry , computer science , operating system
1. The currents underlying the graded impulses in small cultured hippocampal neurons from rat embryos were analysed under voltage‐clamp conditions with the tight‐seal whole‐cell recording technique. 2. The leak and capacitative currents induced by a potential step were linearly related to the potential in the range studied (‐60 to ‐100 mV). 3. With steps to potentials more positive than ‐40 mV, at least two different potential‐activated currents were detected: an initial transient current and a delayed sustained one. In addition, 40% of the cells studied showed a delayed transient current. 4. The initial transient current showed sigmoid activation and roughly exponential inactivation. Its reversal potential depended on the Na+ concentration and was close to the Na+ equilibrium potential. Further, it was blocked by 3.0 microM‐tetrodotoxin, and was abolished when choline was substituted for Na+ in the extracellular solution. We concluded that this current was carried mainly by Na+ ions. 5. The delayed sustained current showed sigmoid activation and almost no inactivation within 40 ms. The reversal potential was close to the K+ equilibrium potential. We concluded that this current was carried mainly by K+ ions. 6. The delayed transient current was outward in the potential range studied (‐50 to +120 mV) and did not depend on the pipette Cl‐ concentration. It was assumed that this current was carried mainly by K+ ions. 7. A quantitative description of the initial transient and the delayed sustained currents was developed on the basis of earlier descriptions of excitable membranes.