Calcium/Calmodulin-Modulated Chloride and Taurine Conductances in Cultured Rat Astrocytes
Document Type
Article
Publication Date
1-18-2002
Abstract
Osmotically swollen rat cerebral astrocytes develop an increased anion conductance which can mediate chloride and taurine release. We used whole cell patch clamp to study mechanisms that modulate this conductance. Astrocyte chloride conductance increased within 4 min of exposure to 200 mOsm medium and was 670±123% of its initial value after 15 min (mean±S.E.M.). This conductance was substantially reduced in 0.1 mM extracellular calcium with 20 mM BAPTA added to the electrode solution and was completely inhibited with calcium-free perfusion solution containing 1 mM EDTA (n=4). The conductance increase in 200 mOsm medium also was inhibited in a dose-dependent manner by nimodipine with a calculated Ki of 0.31±0.4 μM and mean±S.E.M. inhibition of 84.4±4% at 100 μM nimodipine. In the presence of 100 μM W-7, a calmodulin antagonist, the mean±S.E.M. conductance increase after 15 min was 223±40% of the initial value while 300 μM W-7 or 100 μM trifluoperazine inhibited the conductance increase completely (n=6). With taurine as the major anion in electrode and perfusion solutions, a significant conductance increase was observed in 200 mOsm medium. This conductance increase was inhibited by 300 μM W-7 or 100 μM nimodipine. We conclude extracellular calcium influx via L-type calcium channels leads to increased astrocyte anion conductance in 200 mOsm conditions via calmodulin-dependent activation of anion channels. Efflux of anionic taurine from swollen astrocytes also may be affected by calcium influx through a similar calcium/calmodulin-dependent process.
Repository Citation
Li, G. Z.,
Liu, Y.,
& Olson, J. E.
(2002). Calcium/Calmodulin-Modulated Chloride and Taurine Conductances in Cultured Rat Astrocytes. Brain Research, 925 (1), 1-8.
https://corescholar.libraries.wright.edu/emergency_medicine/241
DOI
10.1016/S0006-8993(01)03235-8
