Spontaneous intracellular calcium oscillations in cortical astrocytes from a patient with intractable childhood epilepsy (Rasmussen's Encephalitis)
✍ Scribed by Timothy J. Manning Jr.; Harald Sontheimer
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 80 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0894-1491
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✦ Synopsis
Many studies have demonstrated that astrocytes respond with fluctuations in intracellular calcium concentration ([Ca 2ϩ ] i ) and membrane potential following the application of a number of ligands. Moreover, calcium (Ca 2ϩ ) waves that spread through astrocytic syncitia have been described in numerous reports. We had the rare opportunity to study Ca 2ϩ responses in astrocytes obtained from a patient diagnosed with Rasmussen's encephalitis, a rare form of intractable epilepsy. Using the ratiometric fluorescent indicator fura-2, we observed large spontaneous [Ca 2ϩ ] i oscillations. The mean time between initial rise in [Ca 2ϩ ] i and the return to baseline was 5.1 Ϯ 0.19 minutes (SEM; n ϭ 201) and [Ca 2ϩ ] i increased to a mean level of 271 Ϯ 8 nM (SEM; n ϭ 201) from a baseline of 136 Ϯ 6 nM (SEM; n ϭ 201). Removal of Ca 2ϩ from the perfusion solution combined with the addition of the Ca 2ϩ chelator EGTA (2 mM) completely but reversibly eliminated all oscillations suggesting the fluctuations were dependent on Ca 2ϩ flux across the membrane. The percentage of cells undergoing spontaneous changes in [Ca 2ϩ ] i decreased over time in culture. At 10-11 days postsurgery, approximately 70% of the cells were exhibiting this behavior, and by day 23 transients were no longer observed. We did not observe comparable spontaneous [Ca 2ϩ ] i oscillations in rat cortical astrocytes. The potential that the spontaneous [Ca 2ϩ ] i oscillations observed may be a unique feature of epileptic tissues is discussed.