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Sustained increase in intracellular calcium promotes neuronal survival
F Collins1, M F Schmidt, P B Guthrie
1Synergen, Incorporated, Boulder, Colorado 80301.
Summary
Elevated extracellular potassium enhances ciliary ganglion neuron survival by increasing intracellular calcium levels. This calcium influx, mediated by dihydropyridine-sensitive channels, quantitatively determines neuronal survival rates.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Ciliary ganglion neurons normally experience significant developmental cell death.
- The mechanism by which elevated extracellular potassium promotes neuronal survival is not fully understood.
Purpose of the Study:
- To investigate the role of intracellular calcium in potassium-induced survival of ciliary ganglion neurons.
- To determine if elevated potassium directly impacts intracellular calcium concentrations.
Main Methods:
- Culturing ciliary ganglion neurons in varying extracellular potassium concentrations.
- Measuring intracellular calcium levels using fluorescence techniques.
- Utilizing dihydropyridine calcium channel blockers to assess channel involvement.
Main Results:
- Depolarizing extracellular potassium concentrations (5 to 40 mM) caused a sustained increase in intracellular calcium.
- Optimal potassium concentrations for survival correlated with higher intracellular calcium levels.
- Calcium channel blocker PN200-110 inhibited potassium-mediated survival and calcium increase.
- A quantitative correlation was observed between neuronal survival percentage and intracellular calcium concentration.
Conclusions:
- Elevated extracellular potassium promotes ciliary ganglion neuron survival by opening dihydropyridine-sensitive calcium channels.
- Sustained increases in intracellular calcium are critical for neuronal survival.
- Intracellular calcium concentration quantitatively dictates the number of surviving neurons.