Optical stimulation and imaging of functional brain circuitry in a segmented laminar flow chamber

Abstract

Microfluidic technology is emerging as a useful tool for the study of brain slices, offering precise delivery of chemical factors along with robust oxygen and nutrient transport. However, continued reliance upon electrode-based physiological recording poses inherent limitations in terms of physical access as well as the number of sites that can be sampled simultaneously. In the present study, we combine a microfluidic laminar flow chamber with fast voltage-sensitive dye imaging and laser photostimulation via caged glutamate to map neural network activity across large cortical regions in living brain slices. We find that the closed microfluidic chamber results in greatly improved signal-to-noise performance for optical measurements of neural signaling. These optical tools are also leveraged to characterize laminar flow interfaces within the device, demonstrating a functional boundary width of less than 100 μm. Finally, we utilize this integrated platform to investigate the mechanism of signal propagation for spontaneous neural activity in the developing mouse hippocampus. Through the use of localized Ca2+ depletion, we provide evidence for Ca2+-dependent synaptic transmission.

Microfluidic technologies for ex vivo tissue biopsies: A review

“…4a). Similar devices have been presented in (Ahrar et al, 2013;Blake et al, 2010;Thomas et al, 2013). In these platforms, relatively large regions are exposed to a specific condition.…”

Microfluidic Platforms for the Investigation of Intercellular Signalling Mechanisms

“…Reproduced with permission. [ 70 ] Copyright 2013, The Royal Society of Chemistry. (Figure 7 B: ii).…”

“…Reproduced with permission . Copyright 2010, Elsevier Inc. (B) Ahrar et al's microfluidic laminar flow chamber; (i) show the two distinct chemical environments in the chamber (coloured red and blue) with sharp delineation created by the segmented laminar flow; (ii) Fast voltage‐sensitive dye imaging of spontaneous network activity in the developing hippocampal slices over time. Neural activity events were initiated in CA3 and propagated in forwards and backwards directions towards CA1 and DG, respectively.…”

“…(iii) Ca 2+ is globally diffused over the brain slice; (iv) Under the conditions of (iii), reverse signal propagation towards DG when photostimulation occurred; (v) & (vi) Segmented Ca 2+ delivery using laminar flow prevents the initiated reverse signal propagation from continuing past the boundary of the Ca 2+ interface (red dashed line). Reproduced with permission . Copyright 2013, The Royal Society of Chemistry.…”

“…Alternatively, optical methods for physiological recording were employed by Ahrar and colleagues for analysis of neural activity in living hippocampal slices. Utilising brain slices has the advantage over neuronal cell cultures of retaining neural connectivity complexity.…”