Application of micro electrode arrays (MEAs) as an emerging technology for developmental neurotoxicity: evaluation of domoic acid- induced effects in primary cultures of rat cortical neurons

Abstract

Due to lack of knowledge only a few industrial chemicals have been identified as developmental neurotoxicants. Current developmental neurotoxicity (DNT) guidelines (OECD TG 426 and EPA712-C-98-239) are based entirely on in vivo studies that are both time consuming and costly. Consequently, there is a high demand to develop alternative in vitro methods for initial screening to prioritise chemicals for further DNT testing. One of the most promising tools for neurotoxicity assessment is the measurement of neuronal electrical activity using micro electrode arrays (MEA) that provides a functional and neuronal specific endpoint that until now has been used mainly to detect acute neurotoxicity. Here, electrical activity measurements were evaluated to be a suitable endpoint for the detection of potential developmental neurotoxicants. Initially, primary cortical neurons grown on MEA chips were characterized for different cell markers (neural precursor cells, neurons and astrocytes) over time, using immunocytochemistry to evaluate if the model could be suitable for DNT testing. Our results show that primary cortical neurons could be a promising in vitro model for DNT testing since some of the most critical neurodevelopment processes such as progenitor cell commitment, proliferation and differentiation of astrocytes and maturation of neurons are present. To evaluate if electrical activity could be a suitable endpoint to detect chemicals with DNT effects primary cortical neurons grown on MEA were exposed to domoic acid (DoA), a potential developmental neurotoxicant for up to 4 weeks. Long term exposure to a low concentration (50 nM) of DoA increased the basal spontaneous electrical activity as measured by spike and burst rates, as compared to the control cultures. Moreover, the effect induced by the GABAA receptor antagonist bicuculline was significantly lower in the DoA treated cultures than in the untreated ones. The MEA measurements indicate that chronic exposure to DoA changed the spontaneous electrical activity leading to the possible neuronal mal functioning. The obtained results suggest that the MEA could be a useful tool to identify compounds with DNT potential.