Multi-electrode array (mea): the macroscopic view of neuronal network
The MEA technology enables parallel and multi-site extra-cellular recordings within a single brain slice and provides an exceptional macroscopic view of neuronal networks.
MEA recordings allow mid-throughput testing capabilities for compound screening and profiling.
What is a MEA?
A Multi-Electrode Array is an array made of microscopic metal electrodes (10-30 μm of diameter) distributed on a small surface area (~0.8-6 mm²). They are either regularly distributed or they can be arranged to match closely the spatial organization of the brain region investigated. These small electrodes (coated with an inert and biocompatible metal) are used for recording electrical signals related to neuronal activities within the slice.
What are the advantages of MEA recording?
Your compound can be evaluated in vitro under the most physiologically relevant conditions.
As mentioned in the introduction, it is possible to prepare and keep alive rodent brain slices (250-500 μm of thickness). These slices can be prepared from many different brain regions with all neurons and glial cells in place and connected to each other, as they are in vivo. In addition, all receptors, channels, enzymes, are the native ones with all signaling and regulating pathways being functional.
MEA recordings increase the robustness of the data.
The ability to record multiple evoked-responses in parallel at different electrodes within a single slice and within the same region of interest increases the reliability of the data and their subsequent statistical processing.
MEA recordings performed in a single brain slice provide an exceptional macroscopic view of neuronal networks.
Region-specific effects can be readily observed over the MEA electrode surface area. As an example, layer-specific activities can be resolved into stratified structures such as hippocampus or cortex slices.
MEA recordings can facilitate the screening of a series of compounds in parallel, with a remarkably quick turnaround (midthroughput screening).
MEA recordings constitute a well-suited technique for functional series of compound testing as they are much faster than classical glass electrode recordings and as they can be standardized.
Patch-clamp: the microscopic view of neuronal network
This technology provides the highest resolution for electrophysiological recordings from single neuron down to single channel thanks to the different recording configurations (whole-cell, perforated-patch, cell-attached, outside-out).
Very precise physiological and pharmacological questions could be addressed with this technique, clearly dedicated to the understanding of mechanisms of action.
How does it work?
Patch-Clamp recording is performed with borosilicate electrodes of 1-2 μm tip diameter.
A pipette containing electrolyte solution is tightly sealed onto the neuronal membrane and isolates a part of the membrane (patch) electrically. Currents fluxing through the channels in this patch hence flow into the pipette and can be recorded by an electrode that is connected to a highly sensitive differential amplifier. The pipette tip makes a giga-ohm seal contact with the neuronal membrane. Recording this current allows conclusions about the membrane conductance.
Benefits of patch-clamp technique
The advantages of patch-clamp recordings are: