Excitatory amino acid-induced alterations of cytoplasmic free Ca2+ individual cerebellar granule neurons: Role in neurotoxicity
✍ Scribed by Dr. D. Milani; D. Guidolin; L. Facci; T. Pozzan; M. Buso; A. Leon; S. D. Skaper
- Publisher
- John Wiley and Sons
- Year
- 1991
- Tongue
- English
- Weight
- 860 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0360-4012
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✦ Synopsis
The effects of glutamate on intracellular free CaZ+, [Ca2+Ii, and neurotoxicity were compared in cerebellar granule neurons in vitro. [Ca2+Ii was measured with fura-2 and digital fluorescence imaging microscopy; neurotoxicity was monitored using a vital dye and colorimetric analysis. Glutamate produced dosedependent increases in [Ca2+Ii, which tended to be transient for glutamate concentrations in a range of 0.01-0.5 p M and sustained for higher levels of glutamate. The ED,, for the [Ca2+Ii response to glutamate was 6 pM. The LD,, for glutamate-induced neurotoxicity was similar, i.e., 10 pM. The effect of glutamate on [Ca2+Ii was greatly diminished when external Ca2+ was removed and blocked by Mg2+ or N-methyl-D-aspartate (NMDA)-type receptor antagonists. The latter conditions as well as preloading granule neurons with the intracellular Caz+ chelator quin2 largely prevented glutamate cytotoxicity. The neurotoxic effect of glutamate required incubations with the stimulus for 1&20 min at 25OC. Withdrawal of glutamate after this period was accompanied by a prolonged alteration in [Ca2+Ii. Pretreatment of the cells with the ganglioside GM1 reduced this late increase in [Ca2+Ii as well as the neurotoxic effects of glutamate. This indicates that glutamate-induced neurotoxicity results from a composite of diverse temporal alterations in Ca2+ homeostasis and that blunting any of these components reduces excitotoxicity .