Inhibitory Action of Nebracetam on Various Stimuli-Evoked Increases in Intracellular Ca²⁺ Concentrations in Cultured Rat Cerebellar Granule Cells

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Nebracetam (10-100 μM) dose-dependently inhibited increases in intracellular Ca²⁺ concentrations evoked by various stimuli in cultured rat cerebellar granule cells. The magnitude of the nebracetam (100 μM)-induced inhibition of L-glutamate- and N-methyl-D-aspartate-evoked Ca²⁺ responses was 1.5-fold and 1.7-fold greater, respectively, than the inhibition of the high K⁺-evoked response. These findings suggest that in cultured cerebellar granule cells, nebracetam attenuates the external Ca²⁺ influx derived from the activation of N-methyl-D-aspartate receptor-gated rather than voltage-gated Ca²⁺ channels.