CFP and central nervous system cancer: In the present study, we characterized the effect of neuroactive aminoacids released by glioma cells on neuronal [Cl−]i, taking advantage of a genetically encoded CFP/YFP-based ratiometric Cl-Sensor (Markova et al., 2008; Bregestovski et al., 2009; Waseem et al., 2010), which was transiently expressed in cultured hippocampal neurons.