Dataset Information

Defining parameters of specificity for bioluminescent optogenetic activation of neurons using in vitro multi electrode arrays (MEA).

ABSTRACT: In Bioluminescent Optogenetics (BL-OG) a biological, rather than a physical, light source is used to activate light-sensing opsins, such as channelrhodopsins or pumps. This is commonly achieved by utilizing a luminopsin (LMO), a fusion protein of a light-emitting luciferase tethered to a light-sensing opsin. Light of the wavelength matching the activation peak of the opsin is emitted by the luciferase upon application of its small molecule luciferin, resulting in activation of the fused opsin and subsequent effects on membrane potential. Using optimized protocols for culturing, transforming, and testing primary neurons in multi electrode arrays, we systematically defined parameters under which changes in neuronal activity are specific to bioluminescent activation of opsins, rather than due to off-target effects of either the luciferin or its solvent on neurons directly, or on opsins directly. We further tested if there is a direct effect of bioluminescence on neurons. Critical for assuring specific BL-OG effects are testing the concentration and formulation of the luciferin against proper controls, including testing effects of vehicle on LMO expressing and of luciferin on nonLMO expressing targets.

SUBMITTER: Prakash M

PROVIDER: S-EPMC6395573 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Defining parameters of specificity for bioluminescent optogenetic activation of neurons using in vitro multi electrode arrays (MEA).

Prakash Mansi M Medendorp William E WE Hochgeschwender Ute U

Journal of neuroscience research 20180828 3

In Bioluminescent Optogenetics (BL-OG) a biological, rather than a physical, light source is used to activate light-sensing opsins, such as channelrhodopsins or pumps. This is commonly achieved by utilizing a luminopsin (LMO), a fusion protein of a light-emitting luciferase tethered to a light-sensing opsin. Light of the wavelength matching the activation peak of the opsin is emitted by the luciferase upon application of its small molecule luciferin, resulting in activation of the fused opsin an ...[more]

PMID: 30152529

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Project description:BackgroundMulti-electrode arrays (MEAs) have become popular tools for recording spontaneous and evoked electrical activity of excitable tissues. The majority of previous studies of synaptic transmission in brain slices employed MEAs with planar electrodes that had limited ability to detect signals coming from deeper, healthier layers of the slice. To overcome this limitation, we used three-dimensional (3D) MEAs with tip-shaped electrodes to probe plasticity of field excitatory synaptic potentials (fEPSPs) in the CA1 area of hippocampal slices of 129S5/SvEvBrd and C57BL/6J-TyrC-Brd mice.ResultsUsing 3D MEAs, we were able to record larger fEPSPs compared to signals measured by planar MEAs. Several stimulation protocols were used to induce long-term potentiation (LTP) of synaptic responses in the CA1 area recorded following excitation of Schäffer collateral/commissural fibres. Either two trains of high frequency tetanic stimulation or three trains of theta-burst stimulation caused a persistent, pathway specific enhancement of fEPSPs that remained significantly elevated for at least 60 min. A third LTP induction protocol that comprised 150 pulses delivered at 5 Hz, evoked moderate LTP if excitation strength was increased to 1.5x of the baseline stimulus. In all cases, we observed a clear spatial plasticity gradient with maximum LTP levels detected in proximal apical dendrites of pyramidal neurones. No significant differences in the manifestation of LTP were observed between 129S5/SvEvBrd and C57BL/6J-TyrC-Brd mice with the three protocols used. All forms of plasticity were sensitive to inhibition of N-methyl-D-aspartate (NMDA) receptors.ConclusionPrincipal features of LTP (magnitude, pathway specificity, NMDA receptor dependence) recorded in the hippocampal slices using MEAs were very similar to those seen in conventional glass electrode experiments. Advantages of using MEAs are the ability to record from different regions of the slice and the ease of conducting several experiments on a multiplexed platform which could be useful for efficient screening of novel transgenic mice.

Project description:Objective.Microelectrode arrays are standard tools for conducting chronic electrophysiological experiments, allowing researchers to simultaneously record from large numbers of neurons. Specifically, Utah electrode arrays (UEAs) have been utilized by scientists in many species, including rodents, rhesus macaques, marmosets, and human participants. The field of clinical human brain-computer interfaces currently relies on the UEA as a number of research groups have clearance from the United States Federal Drug Administration (FDA) for this device through the investigational device exemption pathway. Despite its widespread usage in systems neuroscience, few studies have comprehensively evaluated the reliability and signal quality of the Utah array over long periods of time in a large dataset.Approach.We collected and analyzed over 6000 recorded datasets from various cortical areas spanning almost nine years of experiments, totaling 17 rhesus macaques (Macaca mulatta) and 2 human subjects, and 55 separate microelectrode Utah arrays. The scale of this dataset allowed us to evaluate the average life of these arrays, based primarily on the signal-to-noise ratio of each electrode over time.Main results.Using implants in primary motor, premotor, prefrontal, and somatosensory cortices, we found that the average lifespan of available recordings from UEAs was 622 days, although we provide several examples of these UEAs lasting over 1000 days and one up to 9 years; human implants were also shown to last longer than non-human primate implants. We also found that electrode length did not affect longevity and quality, but iridium oxide metallization on the electrode tip exhibited superior yield as compared to platinum metallization.Significance.Understanding longevity and reliability of microelectrode array recordings allows researchers to set expectations and plan experiments accordingly and maximize the amount of high-quality data gathered. Our results suggest that one can expect chronic unit recordings to last at least two years, with the possibility for arrays to last the better part of a decade.

Dataset Information

Defining parameters of specificity for bioluminescent optogenetic activation of neurons using in vitro multi electrode arrays (MEA).

Publications

Defining parameters of specificity for bioluminescent optogenetic activation of neurons using in vitro multi electrode arrays (MEA).

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