Enhancement of voltage-gated Ca2+ currents induced by daily stimulation of hippocampal neurons with glutamate.
The regulation of calcium channel currents (ICa) induced by daily stimulation (1 hr) with 10 microM glutamate was studied in full differentiated hippocampal cells in culture. We report a specific enhancement of the high-voltage-activated current type (HVA ICa) ongoing over days. The density of HVA ICa increased about twofold after the second glutamate session, and this enhancement was still observed after the fifth day of treatment, while low-voltage-activated calcium currents (LVA ICa) remained unchanged. During glutamate application, a transient increase of intracellular calcium (Cai) was observed, followed by a slow decay within 2-3 min, and substantial recovery in about 10 min. Similarly, Cai transients induced by periodic membrane depolarization mimicked the long-term effect of glutamate on ICa. These results demonstrate for the first time an increase of ICa in a time frame of days. Since the effect of glutamate on ICa was prevented by cycloheximide, neosynthesis of channel proteins presumably supports this enhancement.
García
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Department of Neurophysiology, Max-Planck-Institut für Psychiatrie, Martinsried, Germany.
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D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D003513:Cycloheximide / Q000494:pharmacology; D004553:Electric Conductivity / Q000187:drug effects; D004558:Electric Stimulation; D004594:Electrophysiology / Q000379:methods; D004622:Embryo, Mammalian; D005971:Glutamates / Q000494:pharmacology*; D018698:Glutamic Acid; D006624:Hippocampus / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D017966:Pyramidal Cells / Q000187:drug effects / Q000502:physiology; D051381:Rats; D013997:Time Factors
D015220:Calcium Channels; D005971:Glutamates; D018698:Glutamic Acid; D011189:Potassium Chloride; D015763:2-Amino-5-phosphonovalerate; D003513:Cycloheximide; D002118:Calcium