A Long-Term Electrical Connection to a Cultured Hippocampal Slice
Steve M. Potter and Jerry Pine
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In collaboration with the laboratory of Yu-Chong Tai in Electrical Engineering, we designed and fabricated neuron probes (`neuroprobes') out of silicon that will hold several neurons in close proximity to electrodes by trapping them within tiny wells. (see diagram, on home page)
By culturing the probe (with trapped cells) next to or within a slice from a rat hippocampus, we will establish a long-term connection to cells within the slice when neurites from the trapped cells extend from the wells and make synaptic contacts with neurons in the slice. This work was conducted in cooperation with the laboratory of Gyorgi Buzsaki at Rutgers under the NIH Neural Prosthesis Program. Buszaki is conducting similar experiments with living rats.
Both electrophysiology and post-mortem studies on rats with implanted neuron probes will tell us much about the success of the probe at interfacing with the host's neural tissue. However, in order to monitor and understand the process of probe integration, we observe this process while it happens, in the organotypic hippocampal slice. We have successfully maintained hippocampal slices on permeable membranes in culture for several weeks, by the method of Stoppini et al. (1991).
We developed methods to stain the probe neurons with fluorescent dyes to allow the visualization of neurite outgrowth from the wells into the slice. We intend to examine the effect of stimulation of probe neurons on their synaptic integration with the slice.
In collaboration with Prof. Scott Fraser, we constructed a high-speed CCD camera (1000 fps) that will allow us to image neural activity in the slice using voltage-sensitive dyes. Thus, using a combination of optical and electrophysiological techniques, we will be able to assess the influence of the probe neurons on the activity of the slice, as well as monitor slice activity via the probe neurons.
Reference
Stoppini, L., Buchs, P.-A. and Muller, D. (1991) A simple method for organotypic cultures of nervous tissue. J. Neurosci. Methods 37: 173-182.
March 1999 Steve Potter (steve.potter@bme.gatech.edu)