We have recently found that L-glutamate suppresses morphological changes of astrocytes induced by amyloid β protein, adenosine 3', 5'-cyclic monophosphate or phorbol ester in culture. To test the possibility that L-glutamate affects organization of the cytoskeleton, we investigated its effect on morphological changes induced by disruption of actin filaments with cytochalasin B. Cultured rat cortical astrocytes exhibited flat, polygonal morphology in the absence of stimulation, and changed into process-bearing stellate cells following treatment with cytochalasin B (50 μM). L-Glutamate strongly suppressed the stellation induced by cytochalasin B. The effect of L-glutamate was mimicked by D- and L-aspartate and transportable glutamate uptake inhibitors. These results suggest that glutamate transporter activity leads to cytoskeletal actin organization in astrocytes.