Olfactory dysfunction is one of the earliest symptoms of neurodegenerative disorders like Alzheimer's disease and Parkinsonism. A dominant hypothesis is that these diseases have a primary cholinergic etiology. Understanding how this system modulates olfactory processing, therefore, sets the stage for early detection and intervention. Acetylcholine modulates olfactory perceptual learning and working memory. This modulation of olfaction results from the incoming cholinergic innervation from the basal forebrain and subsequent activation of two classes of cholinergic receptors - the muscarinic acetylcholine receptors and nicotinic acetylcholine receptors (nAChRs). In this proposal, we examine the role of nAChRs in modulating the excitability of mitral cells in the mouse main olfactory bulb. Using a synergistic approach incorporating olfactory slice electrophysiology and awake behaving recording we ask how interactions between various nAChR subtypes in the olfactory bulb result in the modulation of the glomerular output to incoming odor signals thereby affecting behavior. The proposal examines this question at multiple levels. In olfactory bulb slices we examine the nAChR modulation of the glomerular microcircuit using gene knockout mice, pharmacology, electrophysiology and calcium imaging. We test the model that nAChR modulation of glomerular output is due to efficient feedback inhibition from periglomerular (PG) cells. We also test a novel idea that effective inhibition of glomerular output is driven by amplification of GABA release due to PG-PG interactions. Using optogenetic approaches, we will examine how the glomerular circuit is modulated by ACh released from cholinergic fibers. Timing of transmitter release, relative to incoming odor input, will be examined both in slices, as well as with recordings from awake behaving animals. The research proposed here will greatly enhance our understanding of the principles governing cholinergic modulation in the brain to lay the foundation for rational drug design to treat neurodegenerative disorders.

Public Health Relevance

In humans, cholinergic signaling is thought to be involved in disorders of the sense of smell in diseases such as Parkinson's, Alzheimer's and schizophrenia. This grant will study cholinergic modulation of signal processing in the olfactory bulb, a fundamental process that plays an important role in modulating the sense of smell. Importantly, studying cholinergic modulation in the olfactory system will have important implications for the treatment of neurodegenerative disorders.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Research Project (R01)
Project #
5R01DC008855-10
Application #
9483270
Study Section
Somatosensory and Chemosensory Systems Study Section (SCS)
Program Officer
Sullivan, Susan L
Project Start
2007-06-01
Project End
2019-05-31
Budget Start
2018-06-01
Budget End
2019-05-31
Support Year
10
Fiscal Year
2018
Total Cost
Indirect Cost
Name
University of Colorado Denver
Department
Physiology
Type
Schools of Medicine
DUNS #
041096314
City
Aurora
State
CO
Country
United States
Zip Code
80045
Spindle, Michael S; Parsa, Pirooz V; Bowles, Spencer G et al. (2018) A dominant role for the beta 4 nicotinic receptor subunit in nicotinic modulation of glomerular microcircuits in the mouse olfactory bulb. J Neurophysiol 120:2036-2048
Ryan, Duncan P; Gould, Elizabeth A; Seedorf, Gregory J et al. (2017) Automatic and adaptive heterogeneous refractive index compensation for light-sheet microscopy. Nat Commun 8:612
Vijayaraghavan, Sukumar; Sharma, Geeta (2015) Editorial: Brain cholinergic mechanisms. Front Synaptic Neurosci 7:14
Parsa, Pirooz Victor; D'Souza, Rinaldo David; Vijayaraghavan, Sukumar (2015) Signaling between periglomerular cells reveals a bimodal role for GABA in modulating glomerular microcircuitry in the olfactory bulb. Proc Natl Acad Sci U S A 112:9478-83
D'Souza, Rinaldo D; Vijayaraghavan, Sukumar (2014) Paying attention to smell: cholinergic signaling in the olfactory bulb. Front Synaptic Neurosci 6:21
D'Souza, Rinaldo D; Parsa, Pirooz V; Vijayaraghavan, Sukumar (2013) Nicotinic receptors modulate olfactory bulb external tufted cells via an excitation-dependent inhibitory mechanism. J Neurophysiol 110:1544-53
Hellier, Jennifer L; Arevalo, Nicole L; Smith, Lynelle et al. (2012) ýý7-Nicotinic acetylcholine receptor: role in early odor learning preference in mice. PLoS One 7:e35251
D'Souza, Rinaldo D; Vijayaraghavan, Sukumar (2012) Nicotinic receptor-mediated filtering of mitral cell responses to olfactory nerve inputs involves the ?3?4 subtype. J Neurosci 32:3261-6
Grybko, Michael J; Hahm, Eu-Teum; Perrine, Wesley et al. (2011) A transgenic mouse model reveals fast nicotinic transmission in hippocampal pyramidal neurons. Eur J Neurosci 33:1786-98
Doucette, Wilder; Gire, David H; Whitesell, Jennifer et al. (2011) Associative cortex features in the first olfactory brain relay station. Neuron 69:1176-87

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