Techniques for imaging of electrical activity in intact nervous systems hold great promise for the study of how networks of neurons work and how collections of neurons generate behavior as an emergent process through their complex synaptic interactions. Voltage imaging depends critically on the use of optical probes that convert changes in membrane potential into a detectable optical signal. Probes currently in wide use have serious limitations that impede progress in the investigation of neural networks with voltage imaging. This proposal will develop a new and novel approach to voltage imaging in living cells in brain slices from transgenic mice. This plan will extend a method termed hybrid voltage sensing (hVOS), which employs a genetically encoded fluorescent protein expressed in cells and targeted to the cell surface. Cells expressing this protein are treated with the synthetic compound, dipycrylamine (DPA), which absorbs light emitted by the fluorescent protein. DPA enters the hydrophobic interior of the plasma membrane lipid bilayer, and through resonant energy transfer, DPA can absorb light emitted by the membrane targeted protein, and thus quench its fluorescence. Because DPA carries a negative charge, it moves within the lipid bilayer in response to membrane potential. When the distance between DPA and the membrane targeted fluorescent protein changes, the amount of quenching changes so that detected fluorescence yields information about membrane potential. The first Specific Aim of this project is to perform critical tests of various fluorescent proteins to find one with optimal performance in hVOS imaging. The second Specific Aim will develop a method of hVOS that employs two fluorophores targeted to opposite faces of the plasma membrane. This will enable investigators to perform ratiometric calculations of membrane potential from two hVOS signals. These probes will enable investigators to target specific types of cells, either by the production of transgenic animals or by a variety of other molecular targeting techniques. In this way high-performance hVOS probes will serve as valuable tools for investigating network behavior, and thus contribute broadly to advances in many basic and applied areas of neuroscience.

Public Health Relevance

This project will advance understanding of mental illness and neurological diseases by giving investigators general tools for the study of electrical activity in the brain. By studying electrical activity in specific kinds of neurons, researchers will learn how different kinds of cells contribute to brain function. This will allow clinical scientists to decide which types of neurons to target with drugs to correct abnormalities in neural function.

National Institute of Health (NIH)
National Institute of Neurological Disorders and Stroke (NINDS)
Exploratory/Developmental Grants (R21)
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Neurotransporters, Receptors, and Calcium Signaling Study Section (NTRC)
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Stewart, Randall R
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University of Wisconsin Madison
Schools of Medicine
United States
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Wright, Brandon J; Jackson, Meyer B (2014) Long-term potentiation in hilar circuitry modulates gating by the dentate gyrus. J Neurosci 34:9743-53
Jackson, Meyer B (2013) Recall of spatial patterns stored in a hippocampal slice by long-term potentiation. J Neurophysiol 110:2511-9
Wang, Dongsheng; McMahon, Shane; Zhang, Zhen et al. (2012) Hybrid voltage sensor imaging of electrical activity from neurons in hippocampal slices from transgenic mice. J Neurophysiol 108:3147-60
Wang, Dongsheng; Zhang, Zhen; Chanda, Baron et al. (2010) Improved probes for hybrid voltage sensor imaging. Biophys J 99:2355-65