Our earlier studies have shown that cerebrospinal fluid (CSF) of amyotrophic lateral sclerosis (ALS) patients causes death of motor neurons, both in in-vitro as well as in-vivo. There was an aberrant phosphorylation of neurofilaments in cultured spinal cord neurons of chick and rats following exposure to CSF of ALS patients (ALS-CSF). Other features of neurodegeneration, such as swollen neuronal soma and beading of neurites were also observed. In neonatal rat pups exposed to ALS-CSF, we observed phosphorylated neurofilaments in the soma of spinal motor neurons in addition to the increased lactate dehydrogenase activity and reactive astrogliosis. The present study examines the effect of ALS-CSF on the expression of glial glutamate transporter (GLT-1) in embryonic rat spinal cord cultures as well as in spinal astrocytes of neonatal rats. Immunostaining suggested a decrease in the expression of GLT-1 by astrocytes both in culture and in-vivo following exposure to ALS-CSF. Quantification of Western blots confirmed the decreased expression of GLT-1. Our results provide evidence that toxic factor(s) present in ALS-CSF depletes GLT-1 expression. This could lead to an increased level of glutamate in the synaptic pool causing excitotoxicity to motor neurons, possibly by triggering the 'glutamate-mediated toxicity-pathway'.