- At present, most neurotoxicological studies in the field of microelectrode array (MEA) technology are based on in vivo or in vitro animal models, particularly in mice or rats. These models contributed much to our knowledge about molecular and cellular mechanisms of neurotoxins affecting the central nervous system. Yet, animal models are not necessarily capable to forecasting the effectiveness of treatment in clinical trials. Therefore the development and characterization of suitable neuronal cell models derived from human cells is emerging in the field of toxicity testing. In this study, we present neurospheres (NS) as a new three dimensional (3D) neuronal cell model based on human embryonic stem cells (hESC), coupled onto microelectrode arrays (MEA). This cell-based assay serves as platform to investigate effects of neuroactive substances on network communication. In order to characterize the neurospheres’ reaction, the well-known GABA receptor antagonist bicuculline and the sodium channel blocker carbamazepine are applied. Preliminary results reveal anticipated and physiologically reasonable alterations in network activity. Thus, we have the first evidence that hESC derived NS are a promising 3D cell model for neurotoxicity testing. In further studies, this model will be used to investigate effects of ionizing radiation on network signaling.