A Multielectrode Microcompartment Platform for Signal Transduction in the Nervous System
Ravula, Surendra Kumar
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This dissertation presents the development of a multielectrode microcompartment platform for understanding signal transduction in the nervous system. The design and fabrication of the system and the characterization of the system for pharmacological and electrophysiological measurements of cultured neurons is presented in this work. The electrophysiological activity of cultured dorsal root ganglion (DRG) neurons and cortical neurons is shown on the MEA substrate. These recordings were measured and tied to the toxicological effects of the chemotherapeutic drug vincristine on DRGs. Conventional electrophysiological recordings (via a patch micropipette) are made routinely to record action potentials and ion channel activity in neurons. Moreover, Campenot chambers (traditional compartmented culture systems) have been used for the last thirty years to study the selective application of drugs to neurons. Both of these techniques are useful and well established; however they have their limitations. For instance, Campenot chambers cannot be used very well for small processs-producing neurons, since the barriers are difficult to tranverse. Moreover, conventional patch recordings are labor-intensive, especially when more than one microelectrode needs to be positioned. The developed system is composed of a two compartment divider, each compartment capable of housing axons or cell bodies. Underneath the divider, the substrate has 60 electrodes, arranged in several lines to accommodate several different neurite tracks. Neurons can be stimulated and their activity can be recorded in both of the compartments. The neurotoxin and chemotherapeutic drug vincristine was tested in the system on the DRGs. The drug caused length-dependent axonal degeneration in the DRGs when applied locally. Moreover, electrophysiological activity in both compartments showed that only the activity in the axonal compartment was affected, leading us to believe that the mechanism behind the degeneration is localized to the distal axon.