Recent evidence indicates that extracellular ATP plays an important role in cellular signaling and can act as a neuromodulator in sensory systems. Noxious stimuli, cell damage and certain pathophysiological conditions can evoke release of cytosolic ATP. ATP can bind to either of two purinergic receptors: P2Y G-protein-coupled receptors or P2X ion channel-forming receptors. Through either of these receptor subtypes, ATP is able to evoke an increase in intracellular Ca2+ ([Ca2+]i). [Ca2+]i has a key role in regulating the sensitivity of olfactory signal transduction. Odorants bind to specific receptors on olfactory receptor neurons (ORNs), thereby activating a G-protein coupled adenylyl cyclase/ cAMP second messenger cascade, leading to the sequential opening of cAMP-gated (CNG) cation channels and a large localized influx of [Ca2+]i. The increase in [Ca2+]i plays an important role as a third messenger in olfactory transduction. It opens Ca2+-activated Cl- channels, substantially amplifying the generator current. Calcium increases also mediate odor adaptation through modulation of CNG channel activity or of molecules in the transduction cascade. Thus, changes in [Ca2+]i homeostasis could alter the responsiveness of ORNs to stimuli. This application will test the general hypothesis that noxious or trigeminal nerve stimulation of the peripheral olfactory system evokes the release of ATP that modulates responsiveness of olfactory receptor neurons to odor. It will provide the first detailed molecular, pharmacological, electrophysiological, and immunofluorescence characterization of purinergic nucleotide receptors in peripheral mammalian olfactory structures and will distinguish the role of nucleotides in control, signaling, and modulation of olfaction. Because ATP is released during neurotransmission and by noxious stimuli, these studies may elucidate mechanisms for the observed reduction in olfactory sensitivity during exposure to noxious agents.

Agency
National Institute of Health (NIH)
Institute
National Institute on Deafness and Other Communication Disorders (NIDCD)
Type
Small Research Grants (R03)
Project #
5R03DC004953-03
Application #
6637131
Study Section
Special Emphasis Panel (ZDC1-SRB-O (30))
Program Officer
Davis, Barry
Project Start
2001-08-01
Project End
2004-07-31
Budget Start
2003-08-01
Budget End
2004-07-31
Support Year
3
Fiscal Year
2003
Total Cost
$75,000
Indirect Cost
Name
University of Utah
Department
Physiology
Type
Schools of Medicine
DUNS #
009095365
City
Salt Lake City
State
UT
Country
United States
Zip Code
84112
Hegg, Colleen C; Lucero, Mary T (2006) Purinergic receptor antagonists inhibit odorant-induced heat shock protein 25 induction in mouse olfactory epithelium. Glia 53:182-90
Vogalis, Fivos; Hegg, Colleen C; Lucero, Mary T (2005) Ionic conductances in sustentacular cells of the mouse olfactory epithelium. J Physiol 562:785-99
Hegg, Colleen C; Greenwood, Denise; Huang, Wei et al. (2003) Activation of purinergic receptor subtypes modulates odor sensitivity. J Neurosci 23:8291-301
Hegg, Colleen C; Au, Edmund; Roskams, A Jane et al. (2003) PACAP is present in the olfactory system and evokes calcium transients in olfactory receptor neurons. J Neurophysiol 90:2711-9