Kinetic and pharmacological properties of high- and low-threshold calcium channels in primary cultures of rat hippocampal neurons.
The kinetic, permeability and pharmacological properties of Ca currents were investigated in primary cultures of rat hippocampal neurons. The low-voltage-activated (LVA) Ca current turned on positive to -60 mV and fully inactivated in a voltage-dependent way. This current was depressed by nickel (Ni, 40 microM) and amiloride (500 microM) and was insensitive to omega-conotoxin (omega-CgTx) (4 microM) and to the Ca agonist Bay K 8644 (5 microM). The high-voltage-activated (HVA) Ca current turned on positive to -40 mV and inactivated slowly and incompletely. This current was much less sensitive than the LVA current to Ni and amiloride but more sensitive to cadmium. omega-CgTx blocked only partially this current (about 50%) in an irreversible way. Bay K 8644 had a clear agonistic action almost exclusively on the omega-CgTx-resistant HVA current component. The present results suggest that the HVA channels, quite homogeneous for their kinetic properties and sensitivity to holding potentials, can be pharmacologically separated in two classes: (i) omega-CgTx-sensitive and Bay-K-8644-insensitive (omega-S/BK-I) and (ii) omega-CgTx-insensitive and Bay-K-8644-sensitive (omega-I/BK-S), the latter displaying a stronger Ca-dependent inactivation.
Toselli
M
M
Istituto di Fisiologia Generale, Università di Pavia, Italy.
Taglietti
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D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002463:Cell Membrane Permeability / Q000187:drug effects; D002478:Cells, Cultured; D004095:Dihydropyridines / Q000494:pharmacology; D004594:Electrophysiology; D006624:Hippocampus / Q000166:cytology / Q000502:physiology*; D007700:Kinetics; D009474:Neurons / Q000502:physiology*; D009532:Nickel / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D051381:Rats; D020866:omega-Conotoxin GVIA
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004095:Dihydropyridines; D010456:Peptides, Cyclic; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000584:Amiloride; C038806:1,4-dihydropyridine; D009532:Nickel; D020866:omega-Conotoxin GVIA