Assessment of Neuronal Activity Using Microelectrode Array
The eCiphr®Neuro assay uses primary cultures of rat cortical neurons.
Cyprotex’s neuronal assay uses high throughput microelectrode array (MEA) technology to monitor electrophysiological activity.
Neurons grown on microelectrode arrays recapitulate many features of neurons in vivo, including spontaneous activity (spiking and bursting), plasticity, organization and responsiveness to a wide range of neurotransmitters and pharmacological agonists/antagonists1.
This technology provides a unique in vitro system for preclinical drug discovery, neurotoxicity assessment and disease modeling.
The unique capabilities of MEAs to provide functional measurements of network activity, including spontaneous activity, evoked activity, and responses to pharmacological challenges, therefore offers an advantage over other potential screening approaches that rely on biochemical or structural endpoints.
1Robinette BL et al., (2011) Front Neuroeng4; 1-9
eCiphr®Neuro assay protocol
Primary rat cortical neurons
Maestro 48-well MEA system (Axion BioSystems)
Test Article Concentrations
Four concentrations in triplicate (dependent on customer requirements)
Negative control: 0.2% DMSO (vehicle) Positive controls: picrotoxin and domoic acid (at single concentration)
Firing rate (spikes/second) Burst rate (bursts/second) Number of spikes in burst Percent of isolated spikes Coefficient of variation (CV) of the inter-spike intervals (ISI) Burst duration Normalized IQR (inter-quartile range) burst duration Interburst interval Mean ISI-distance (measure of synchrony) Normalized Median Absolute Deviation (MAD) burst spike number Median ISI/Mean ISI
Data from Cyprotex's eCiphr®Neuro assay
Figure 1 Rat cortical neurons stained with Hoechst 33342 and βIII-tubulin/DyLight® 488 and imaged with an ArrayScan VTi.
Figure 2 Change in spontaneous spike activity in rat cortical neurons after drug treatment.
The spontaneous spike activity is recorded in rat cortical neurons using Axion Biosystems microelectrode array Maestro platform. The spike train data is extracted from baseline and post dose measurements and converted to numerical values using a custom Matlab script to characterize firing and burst organization. The negative control 0.2% DMSO (vehicle) caused no change in activity, burst characteristics or synchrony. A distinct pattern of change affecting spike activity, burst characteristics and synchrony is observed with GABAA antagonists picrotoxin and gabazine. A different but significant pattern of activity can be seen with other proconvulsant toxins such as strychnine, a glycine receptor antagonist. Meanwhile complete abolishment of spike activity is observed with the neurotoxin, domoic acid.
Figure 3 Raster plots of spike activity in five individual electrodes before and after 1 hr treatment with 10µM picrotoxin.
Five representative electrodes out of the 16 electrodes in a well are shown over a 150 sec time span. The recorded spike activity of rat cortical neurons is represented by the raster plots which illustrate the structure of typical baseline spike activity for a well compared to its structure following a 10µM dose with the GABAA antagonist picrotoxin. The qualitative visual differences in the dynamics of the spike train are quantified through computation of the spike train features as seen in Figure 2.
Neurological effect in vivo
Decreases neural activity6
Sodium channel blocker
Potassium channel blocker
Increases neural activity10
Glycine receptor antagonist
Table 1 Comparison of eCiphr®Neuro data with neurological effects observed in vivo.
A number of compounds with a range of neurological effects were tested in the eCiphr®Neuro assay using rat cortical neurons. A good correlation was seen with drugs tested in this in vitro assay with their known in vivo effects. Different patterns of change affecting spike activity, burst characteristics and synchrony are observed in GABAA antagonists and other proconvulsants as illustrated in Figure 2.
1 Robinette BL et al, (2011) Front Neuroeng4; Article 1 2 Margineau DG and Wülfert E (1997) Br J Pharmacol122; 1146-1150 3 Mackenzie L et al, (2002) Clin Neurophysiol113(4); 586-596 4 Ono J et al, (1990) Funct Neurol5(4); 345-352 5 Fuentealba J et al, (2011) Neuropharmacology 60; 453-459 6 Levy LM and Degnan AJ, (2013) Am J Neuroradiol34(2); 259-265 7 Hwang DF and Noguchi T (2007) Adv Food Nutr Res52; 141-236 8 Peña F and Tapia R (2000) Neuroscience101(3); 547-561 9 Pulido OM (2008) Mar Drugs6(2); 180-219 10 Hankir MK et al, (2012) Neuroimage59(2); 968-978 11 Kehne JH et al, (1992) Br J Pharmacol106(4); 910-916
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