The long term goal of the proposed experiments is to understand how animals perceive odors. The experiments in the present proposal are designed to improve our understanding of the function and role of the olfactory bulb in this process. Maps of the input to the bulb are available from optical recordings of calcium and pH signals. Here we propose to use optical recording methods to monitor the activity of postsynaptic cells in the olfactory bulb in an in vivo mouse preparation. First, we plan to use bulk injection of calcium dyes and 2-photon microscopy to simultaneously monitor the activity of many (hundreds) of individual neurons in response to odorant presentations. We plan to make these recordings from both juxtaglomerular neurons that surround the glomeruli and from mitral cells which provide the output of the olfactory bulb. The ability to record from many neurons simultaneously should greatly improve our understanding of olfactory bulb function. Second, we propose to use genetically encoded voltage-sensitive (FP-voltage sensor) or calcium- sensitive proteins expressed in the mitral/tufted cells to monitor the output of the bulb in response to odor presentations. A comparison of the output map with the input map would provide a strong statement about the function of the olfactory bulb in odorant processing. We propose modifications to improve the FP-voltage sensor signal-to-noise ratio and response time constant. These improvements would facilitate their use in any cell type in the mammalian brain and thereby contribute to the understanding of many aspects of brain function.
Olfactory function is compromised in a number of human diseases including Alzheimer's disease and Parkinson's disease (Schiffman, 1992;Doty, 2001). In Parkinson's disease and in the Thy1-aSyn mice mouse model of Parkinson's disease reduced odorant sensitivity is one of the earliest detected symptoms (Fleming and Chesselet, 2006). A hallmark of Parkinson's disease is the premature cell death of dopaminergic neurons;a substantial fraction of periglomerular neurons in the olfactory bulb are dopaminergic. Thus the experiments in the present proposal would not only further our basic understanding of olfactory processing but also allow a characterization of the neuronal substrate of the olfactory symptoms in mouse models. In addition, voltage sensitive dyes are regularly used to follow action potential propagation during cardiac arhythmias (e.g. Matiukas et al, 2006;Mironov et al, 2006). The heart is composed of a variety of cell types. Thus specific targeting of FP-voltage sensors would also be very useful in studying the causes treatment of arhythmias.
|Jin, Lei; Baker, Bradley; Mealer, Robbie et al. (2011) Random insertion of split-cans of the fluorescent protein venus into Shaker channels yields voltage sensitive probes with improved membrane localization in mammalian cells. J Neurosci Methods 199:1-9|
|Spors, Hartwig; Wachowiak, Matt; Cohen, Lawrence B et al. (2006) Temporal dynamics and latency patterns of receptor neuron input to the olfactory bulb. J Neurosci 26:1247-59|
|Eugenin, J; Nicholls, J G; Cohen, L B et al. (2006) Optical recording from respiratory pattern generator of fetal mouse brainstem reveals a distributed network. Neuroscience 137:1221-7|
|Wuskell, Joseph P; Boudreau, David; Wei, Mei-de et al. (2006) Synthesis, spectra, delivery and potentiometric responses of new styryl dyes with extended spectral ranges. J Neurosci Methods 151:200-15|
|Zochowski, Michal R; Cohen, Lawrence B (2005) Oscillations in the olfactory bulb carry information about odorant history. J Neurophysiol 94:2667-75|
|Baker, Bradley J; Kosmidis, Efstratios K; Vucinic, Dejan et al. (2005) Imaging brain activity with voltage- and calcium-sensitive dyes. Cell Mol Neurobiol 25:245-82|
|Lam, Ying-Wan; Cohen, Lawrence B; Zochowski, Michal R (2003) Odorant specificity of three oscillations and the DC signal in the turtle olfactory bulb. Eur J Neurosci 17:436-46|
|Wachowiak, Matt; Cohen, Lawrence B; Zochowski, Michal R (2002) Distributed and concentration-invariant spatial representations of odorants by receptor neuron input to the turtle olfactory bulb. J Neurophysiol 87:1035-45|
|Wachowiak, M; Cohen, L B (2001) Representation of odorants by receptor neuron input to the mouse olfactory bulb. Neuron 32:723-35|