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Attenuation of high-voltage-activated Ca2+ current run-down in rat hippocampal CA1 pyramidal cells by NaF
N A Breakwell1, T Behnisch, S J Publicover
1Department of Physiology, Trinity College Dublin, Ireland.
Insights
Sodium fluoride (NaF) application attenuates rundown of high-voltage-activated (HVA) calcium currents in rat hippocampal CA1 neurons. This effect involves calcium-dependent processes and G-protein activation, suggesting a protective mechanism against current rundown.
Area of Science:
- Neuroscience
- Cellular Electrophysiology
Background:
- High-voltage-activated (HVA) calcium currents in CA1 neurons are crucial for synaptic plasticity and neuronal excitability.
- These currents are prone to
- run-down
- during patch-clamp recordings, complicating experimental analysis.
- G-protein signaling pathways are known modulators of ion channel function.
Purpose of the Study:
- To investigate the effect of G-protein activation on HVA calcium current run-down in rat hippocampal CA1 neurons.
- To elucidate the role of calcium-dependent mechanisms in this modulation.
Main Methods:
- Whole-cell, patch-clamp electrophysiology was used to record calcium currents in CA1 neurons.
- The impact of intracellular Sodium Fluoride (NaF), a G-protein activator, on current run-down was assessed.
- The influence of ethyleneglycoltetraacetate (EGTA) on NaF-induced effects was examined to probe calcium dependency.
Main Results:
- HVA calcium currents activated at -80 mV and -40 mV exhibited run-down under control conditions.
- Intracellular NaF significantly attenuated the run-down of currents activated from -40 mV.
- This attenuation by NaF was partially dependent on intracellular calcium levels, as indicated by EGTA experiments.
Conclusions:
- Activation of guanine nucleotide-binding proteins by NaF can attenuate HVA calcium current run-down in hippocampal CA1 cells.
- Calcium-dependent processes appear to mediate or be influenced by this protective effect.
- These findings suggest a novel mechanism for stabilizing calcium currents during electrophysiological studies.
Abstract:
Calcium currents in CA1 neurons from rat hippocampus were studied with the whole-cell, patch-clamp technique. Under control conditions high-voltage-activated (HVA) calcium currents activated from membrane potentials of -80 mV and -40 mV underwent "run-down". The rate of run-down of the current activated from -40 mV was significantly attenuated by inclusion of the G-protein activator NaF (1 mM) in the pipette and also irreversibly attenuated by brief batch application of NaF (10 mM). This effect was significantly reduced by inclusion of high (10 mM) ethyleneglycoltetraacetate (EGTA) concentrations in the pipette, suggesting an involvement of calcium-dependent processes. It is suggested that activation of guanine nucleotide-binding proteins by NaF leads to a long-lasting attenuation of HVA calcium current run-down in hippocampal CA1 cells.