Testing of photolytic uncaging with intraspinal fiber optics as a basis for motor neuroprostheses

Recently, methods have been developed that can 'cage' neurotransmitters, limiting their ability to bind with a receptor and rendering them biologically inert until photolytic uncaging. We explored uncaging of glutamate with implanted fiber optics as a stimulation technology. The spinal cord was bathed in caged glutamate at different concentrations, and a photolysis unit projected brief, spatially concentrated bursts of light into the lumbar spinal cord. Forces generated at the ankle were measured in 3 dimensions. Responses were tested at discrete depths in the lumbar cord, with the strongest responses located in the 900 to 1100 /spl mu/m range. Our results indicate feasibility of this approach for engineering a prosthesis. The advantage of this technology is that excitation, inhibition, and modulation of spinal circuits can be controlled. This technique, when used in a paralyzed individual, would allow greater freedom of movement and independence.