Electrophysiological recording of re-aggregating brain cell cultures on multi-electrode arrays to detect acute neurotoxic effects

Abstract

Neurotoxicity aims to understand how xenobiotics interfere with the function of the nervous system and to unravel their mechanisms of action. Neuronal activity is the primary functional output of the nervous system and deviations from its resting level may indicate toxicity. Consequently, the monitoring of electrophysiological activity in complex cell culture systems appears particularly promising for neurotoxicity assessment. To detect acute neurotoxic effects of chemicals we developed a test system based on the electrophysiological recordings from neural networks in re-aggregating brain cell cultures using multi-electrode arrays. We characterised the electrophysiological properties of the cultures and, using known neurotoxicants, evaluated their usefulness to predict neurotoxic effects. Aggregates displayed evoked field potentials and spontaneous neural activity involving glutamatergic and GABAergic synaptic transmission. Paired pulse inhibition indicated the presence of short-term synaptic plasticity via functional inhibitory networks. Cultures were treated with 0.1-100 microM of trimethyltin chloride (TMT), methyl mercury chloride (MeHgCl), parathion or paraoxon, and with 0.1-100mM of ethanol for up to 100 min. TMT (10 microM), MeHgCl (1 microM) and ethanol (100mM) all decreased the amplitude of evoked field potential. The effect of ethanol was reversible. In contrast paraoxon (10 microM) increased the amplitudes of evoked field potentials while parathion showed no significant effects. The effects of TMT and ethanol on the frequency of spontaneous activity were consistent with those obtained for evoked field potentials. All effects occurred at levels at which cytotoxic injuries were not detectable. Taken together our system expressed electrophysiological properties similar to those of established slice culture preparations. It detected known neurotoxicants at subcytotoxic levels and therefore appears suitable for the assessment of toxic insults specifically interfering with nervous system function, e.g. neuronal activity, synaptic transmission and short-term plasticity. If incorporated into testing strategies, it might represent a valuable tool for the mechanistic assessment of neurotoxic effects.