Abstracts

Rationale: Micro-electrode arrays (MEAs) have been widely utilized to measure neuronal activities in vitro.  The MEA technology offers many unique advantages to investigate neuronal circuitry, interaction and models of learning and memory, development, aging, epileptic disease and neurotoxicity.  While several high-throughput platforms have been utilized for drug screening with cultured cell applications in recent years, there have been limited platforms designed for acute and culture slice applications. Here we present the capabilities of the sensitive MED64-Quad II system, a novel medium-throughput MEA designed specifically for acute or cultured slice applications. Methods: Recordings were made from acute hippocampal slices from 6-8 week old male ICR strain mice and the extracellular signals were obtained at 16 electrodes per slice on Quad II system.  The fEPSP and spontaneous spikes were recorded from CA1 on 4 hippocampal slices simultaneously using the MED64-Quad II System.  The firing frequency per channel and the number of synchronized bursts were analyzed.  Pharmacological agent NMDA, bicuculline, APV were used. Results: Synaptic plasticity can be reliably measured using Quad II system. LTP was developed after TBS stimulation and was maintained for 60 min on Quad II system (N=13). Pretreatment of NMDA receptor antagonist APV at 50uM in bath solution blocked LTP development (N=5). Bath application of NMDA at 10uM produced transient depression of fEPSP, and the depressant effect was reversal after wash. The IC50 of NMDA depressant effect was ~8uM (N=9).  MK-801 pretreatment blocked this NMDA depressant effect (N=7). NMDA depressant effect was independent of GABA_A block (N=8).  In contrast, NMDA increased spike frequency and induced synchronized burst (N=6). The increase in spike rate and synchronized burst were significantly reduced by 50uM APV (P<0.01, N=7), suggesting NMDA induced burst can be used as an epilepsy model and NMDA receptor can be a possible therapeutic target for treatment.  Because of the higher throughput of the MED64-Quad II System, the results from these experiments were obtained much more quickly than with traditional slice recordings; 1 day was needed for each experimental group.  Conclusions: The results of this study indicated that the MED64-Quad II increases throughput and accelerates studies of LTP and epilepsy disease model and its therapeutic drug discovery and shortened experimental time.  This system increases research productivity while maintaining high-sensitivity to detect tiny electrophysiological signals and long lasting fEPSP.  It is a useful tool for disease model research, drug discovery, target validation, compound screening for antiepileptic drug targets and pharmacological studies in acute brain slice applications in vitro. Funding: This work was supported by Alpha MED Scientific, Inc.