1S, 3R-ACPD induces a region of negative slope conductance in the steady-state current-voltage relationship of hippocampal pyramidal cells.

Détails

ID Serval
serval:BIB_3D28E66161B1
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Titre
1S, 3R-ACPD induces a region of negative slope conductance in the steady-state current-voltage relationship of hippocampal pyramidal cells.
Périodique
Journal of Neurophysiology
Auteur(s)
Lüthi A., Gähwiler B.H., Gerber U.
ISSN
0022-3077 (Print)
ISSN-L
0022-3077
Statut éditorial
Publié
Date de publication
1997
Peer-reviewed
Oui
Volume
77
Numéro
1
Pages
221-228
Langue
anglais
Résumé
Synaptic responses mediated by metabotropic glutamate receptors (mGluRs) display a marked voltage-dependent increase in amplitude when neurons are moderately depolarized beyond membrane potential. We have investigated the basis for this apparent nonlinear behavior by activating mGluRs with 1S, 3R-1-aminocyclopentane-1, 3-dicarboxylate (1S, 3R-ACPD; 10 microM) in CA3 pyramidal cells from rat hippocampal slice cultures with the use of the single-electrode voltage-clamp technique. Under control conditions, cells depolarized from resting potential by 10-20 mV responded with delayed outwardly rectifying currents due to activation of voltage- and Ca(2+)-dependent K+ conductances. In contrast, in the continuous presence of 1S, 3R-ACPD, small depolarizations (10-20 mV) induced a delayed inward current. The steady-state current-voltage relationship for this response displayed a region of negative slope conductance at potentials between -55 and -40 mV. The reversal potential of the corresponding 1S,3R-ACPD-sensitive tail currents (-93.0 +/- 2.2 mV, mean +/- SE) was close to the potassium reversal potential, consistent with an mGluR-mediated suppression of K+ current. When external K+ concentration was increased to 8 mM, there was a positive shift in reversal potential to -76.9 +/- 5.1 mV. The depolarization-induced inward current in the presence of 1S,3R-ACPD was blocked by Ba2+ (1 mM). The response was not dependent on changes in intracellular Ca2+ concentration and was insensitive to bath-applied Cs+ (1 mM), ruling out a contribution of Ca(2+)-dependent currents or the inward rectifier lQ. Furthermore, the effect of 1S,3R-ACPD was not mimicked by inhibiting afterhyperpolarizing current and M current with low-Ca2+ saline (0.5 mM Ca2+, 10 mM Mg2+) containing 10 mM tetraethylammonium chloride. A comparison of the responses induced by 1S,3R-ACPD and N-methyl-D-aspartate showed that both induce an inward current with small depolarizations from resting potential but with different kinetics and Mg2+ sensitivity. These results indicate that the suppression of K+ currents in response to activation of mGluRs is markedly voltage dependent, increasing at depolarized potentials and decreasing at hyperpolarized potentials. The negative slope conductance at membrane voltages positive to resting potential may underlie the amplification of mGluR-mediated responses when the membrane potential approaches action potential threshold.
Mots-clé
Animals, Calcium/physiology, Cycloleucine/analogs & derivatives, Cycloleucine/pharmacology, Electrophysiology, Excitatory Amino Acid Agonists/pharmacology, Hippocampus/cytology, Hippocampus/drug effects, Kinetics, Membrane Potentials/drug effects, Membrane Potentials/physiology, N-Methylaspartate/pharmacology, Neural Conduction/drug effects, Patch-Clamp Techniques, Potassium Channels/drug effects, Potassium Channels/physiology, Pyramidal Cells/drug effects, Rats, Receptors, Metabotropic Glutamate/agonists
Pubmed
Web of science
Création de la notice
15/08/2012 9:20
Dernière modification de la notice
20/08/2019 14:33
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