PT  - JOURNAL ARTICLE
AU  - Jianguo Chen
AU  - Kurt H. Backus
AU  - Joachim W. Deitmer
TI  - Intracellular Calcium Transients and Potassium Current Oscillations Evoked by Glutamate in Cultured Rat Astrocytes
AID  - 10.1523/JNEUROSCI.17-19-07278.1997
DP  - 1997 Oct 01
TA  - The Journal of Neuroscience
PG  - 7278--7287
VI  - 17
IP  - 19
4099  - http://www.jneurosci.org/content/17/19/7278.short
4100  - http://www.jneurosci.org/content/17/19/7278.full
SO  - J. Neurosci.1997 Oct 01; 17
AB  - Glutamate responses in cultured rat astrocytes from cerebella of neonatal rats were investigated using the perforated-patch configuration to record membrane currents without rundown of intracellular messenger cascades, and microfluorometric measurements to measure the intracellular Ca2+ concentration ([Ca2+]i) and intracellular pH (pHi) with fura-2 AM and 2′,7′-bis-(2-carboxyethyl)-5,6-carboxyfluorescein acetoxy methylester respectively. In the perforated-patch mode, glutamate evoked single or multiple outward current transients in 82% of the cells, which disappeared when the recording technique was converted into a conventional whole-cell mode. The outward current transients were accompanied by [Ca2+]i transients, whereas pHi fell monophasically, without any sign of oscillation. Pharmacological analysis of the glutamate-induced responses indicated that ionotropic receptor activation evoked an inward current but no outward current transients, and metabotropic receptor activation (of the mGluR1/5 type) elicited outward current transients but no inward current. The outward current transients were reduced in frequency, or even abolished, after depletion of the intracellular Ca2+-stores by the Ca2+-ATPase inhibitor cyclopiaconic acid (10 μm). They reversed near −85 mV and were reduced by tetraethylammonium (10 mm), suggesting that they were caused by K+ channel activation. It is concluded that glutamate evoked these K+ outward current transients by oscillatory Ca2+ release mediated by mGluR activation. The corresponding membrane potential waves across the astroglial syncytium could provide spatial and temporal dynamics to the glial K+ uptake capacity and other voltage-dependent processes.