Neural circuits with long-distance axon tracts for determining functional connectivity.
The cortical circuitry in the brain consists of structurally and functionally distinct neuronal assemblies with reciprocal axon connections. To generate cell culture-based systems that emulate axon tract systems of an in vivo neural network, we developed a living neural circuit consisting of compartmentalized neuronal populations connected by arrays of two millimeter-long axon tracts that are integrated on a planar multi-electrode array (MEA). The millimeter-scale node-to-node separation allows for pharmacological and electrophysiological manipulations to simultaneously target multiple neuronal populations. The results show controlled selectivity of dye absorption by neurons in different compartments. MEA-transmitted electrical stimulation of targeted neurons shows ∼46% increase of intracellular calcium levels with 20 Hz stimulation, but ∼22% decrease with 2k Hz stimulation. The unique feature of long distance axons promotes in vivo-like fasciculation. These axon tracts are determined to be inhibitory afferents by showing increased action potential firing of downstream node upon selective application of γ-aminobutyric acid (GABA) to the upstream node. Together, this model demonstrates integrated capabilities for assessing multiple endpoints including axon tract tracing, calcium influx, network architecture and activities. This system can be used as a multi-functional platform for studying axon tract-associated CNS disorders in vitro, such as diffuse axonal injury after brain trauma.
Tufts University, Department of Biomedical Engineering, Medford, MA 02155, United States.
Min D
MD
Tang-Schomer
Tufts University School of Medicine, Department of Neuroscience, Boston, MA 02111, United States.
Paul
P
Davies
Tufts University, Department of Biomedical Engineering, Medford, MA 02155, United States.
Daniel
D
Graziano
Tufts University, Sackler School of Graduate Biomedical Sciences, Program in Cell, Molecular, and Developmental Biology, Boston, MA 02111, United States.
Amy E
AE
Thurber
Tufts University, Department of Biomedical Engineering, Medford, MA 02155, United States. Electronic address: david.kaplan@tufts.edu.
David L
DL
Kaplan
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000502:physiology*; D001921:Brain / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D004558:Electric Stimulation; D018682:GABA Agents / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D009434:Neural Pathways / Q000187:drug effects / Q000502:physiology; D056325:Neuronal Tract-Tracers; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D056969:Voltage-Sensitive Dye Imaging; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D018682:GABA Agents; D056325:Neuronal Tract-Tracers; D049452:Green Fluorescent Proteins; D005680:gamma-Aminobutyric Acid; D002118:Calcium
Axon tract; Calcium imaging; Electrical stimulation; Inhibitory afferent; Interface; Micropattern