An Optical Probe capable of Activating/Reporting on axon activity in nerves of parasympathetic nervous system would be a boon to researchers working with the pancreas. We are proposing to develop such a Probe using our background and experience in optogenetics in the peripheral nerve, bio-imaging and compact multiphoton microscope design. Current neuro-modulation approaches for the vagus nerve are generally all or nothing events that cause simultaneous changes in heart rate, for example, along with changes in pancreatic function. We propose to develop a novel compact Optogenetic based Optical Probe capable of optically neuromodulating individual afferent and/or efferent axons within nerves of the parasympathetic, or peripheral, nervous system. We seek to read-in or read-out from these nerves with the goal of modulating organs or brain circuits innervated by them. Our central premise is that we can use optics to communicate with axons in a nerve. For optical approaches to work we need to convert action potentials into an optical signal. This can be done using reporter proteins or by some other means that is ancillary to action potential generation. Because nerves do not naturally express optical proteins, we will work with transgenic mice that express these proteins and use these mice to refine our system before making it available for other researchers to use. We will develop a bench-top Optical instrument that can be shared with other research teams to allow us, and them, to interrogate specific fascicles and axons within mouse, and ultimately human, nerves. Our goal here is the vagus nerve and its innervation of the pancreas. The vagus nerve is one of the main conduits into the parasympathetic nervous system. The ability to interface with this nerve gives one the ability to neuromodulate the viscera in one direction and the brain in the other. We are proposing to couple an optical fiber with an electrowetting lens head to allow remote interrogation the vagus nerve with a bench top (i.e. portable) laser system. Integration of miniature (1mm diameter) scale electrowetting electrically tunable optics with an optical fiber-based imaging system will enable two-photon fluorescence imaging of neuron activity by readout of a fluorescent indicator. We will work with our collaborators in the field of pancreatic research to test, refine and demonstrate our ability to activate/report from in-vitro mouse vagus nerves and to see if we can control and/or sense pancreatic responses in the absence of other responses, such as a change in heart rate, using targeted neuro-modulation of specific axons in the vagus in in-vivo transgenic mice experiments.
We are proposing to develop an axon-specific optical probe that we can use to interrogate the neurons of the parasympathetic nervous system with the goal of neuromodulating pancreas secretion of insulin and glucagon. The challenge is to be able to simultaneously detect the activity and stimulate individual axons from the exterior of the nerve i.e. an approach that is non-invasive yet has specificity. We believe we can use optogenetics and Multiphoton microscopy with electrowetting scanning lens technology to achieve this goal. Use of genetically encoded optical proteins (or optogenetics) as tools to stimulate neurons and readout electrical activity is rapidly developing in Neuroscience. Multiphoton microscopy can stimulate or image an optical protein/dye and when combined electrowetting lens can be made small enough for this application to allow us to image deep into a nerve.
|Fontaine, Arjun K; Anderson, Hans E; Caldwell, John H et al. (2018) Optical read-out and modulation of peripheral nerve activity. Neural Regen Res 13:58-61|
|Fontaine, Arjun K; Gibson, Emily A; Caldwell, John H et al. (2017) Optical Read-out of Neural Activity in Mammalian Peripheral Axons: Calcium Signaling at Nodes of Ranvier. Sci Rep 7:4744|