Glutamate‐activated ionic currents in cultured astrocytes from trout: Evidence for the occurrence of non‐N‐methyl‐D‐aspartate receptors

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Abstract
Glutamate‐induced currents were recorded from cultured trout astrocytes with the whole‐cell variation of the patch‐clamp technique. Ninety percent of the tested cells were directly depolarized by the amino acid neurotransmitter in a concentration‐dependent manner. The depolarizing effect was due to an inward current that reversed near 0 mV and was accompanied by a noise increase, indicating the opening of an ion channel. Ion substitution experiments revealed that the glutamate‐induced current was mainly carried by sodium ions but not chloride or calcium ions. The glutamate‐induced response could be mimicked by the neuronal glutamate receptor subtype agonists kainate and quisqualate, while N‐methyl‐D‐aspartate was without detectable effect.