Abstracts - Association for Chemoreception Sciences

the hyperpolarizing conductance and sustain the smooth fast
swimming. We have used RNA interference (RNAi) to test
several candidate genes for possible function as an L-glutamate
receptor and found a gene with sequence homology to the
glutamate binding subunit of an NMDA-like receptor. When
the mRNA for this gene, pGluR1, is depleted using RNAi,
the cells are not attracted to L-glutamate, but continue to be
attracted to D-glutamate. To better understand the signaling
pathway for L-glutamate, we have epitope tagged the pGluR1
protein and found by Western blotting and mass spectrometry
that it is in the membrane of the cell body and cilia. A catalytic
subunit of the ciliary adenylyl-cyclase labeled with GFP does
not co-immuniprecipitate with FLAG-pGluR1. Mammalian
NMDA-like receptors are dependent upon glycine and D-serine,
but the P. tetraurelia chemoresponse to L-glutamate is unaffected
by combinations of glycine and D-serine and L-glutamate.
Acknowledgements: NIH Grant Number 2 P20 RR016435-06 to
the Neuroscience Center of Research Excellence (COBRE to R.
Parsons, PI) for imaging support and NIH grant RO1 GM59988
taste stimuli, including acids and salts, were abolished. Taste
responses also are blocked in a dose-dependent fashion with
application of higher concentrations of AF-353 directly to the
tongue and can be partially recovered upon washout of the drug.
These data clearly indicate that activation of P2X receptors and
therefore ATP release is required for all taste modalities in mice.
Acknowledgements: Funded by NIH grants R01 DC012555,
R01 DC007495, and P30 DC04657 and a gift from Afferent
Pharmaceuticals.
#P166 POSTER SESSION III:
TRIGEMINAL; HUMAN OLFACTORY
PSYCHOPHYSICS; TASTE PERIPHERY
Nonsynaptic Contacts in Rat Circumvallate Taste Buds:
Subsurface Cisternae and Atypical Mitochondria
Ruibiao Yang 1,2 , Amanda E. Bond 1,2 , John C. Kinnamon 1,2
1
Department of Biological Sciences, University of Denver Denver, CO,
USA, 2 Rocky Mountain Taste and Smell Center Aurora, CO, USA
#P165 POSTER SESSION III:
TRIGEMINAL; HUMAN OLFACTORY
PSYCHOPHYSICS; TASTE PERIPHERY
A selective P2X3, P2X2/3 receptor antagonist abolishes
responses to all taste stimuli in mice
Aurelie Vandenbeuch 1,3 , Catherine B. Anderson 1,3 , Anthony P. Ford 4 ,
Steve Smith 4 , Thomas E. Finger 2,3 , Sue C. Kinnamon 1,3
1
University of Colorado School of Medecine, Department of
Otolaryngology Aurora, CO, USA, 2 University of Colorado School of
medecine, Department of Cell and Development Biology Aurora, CO,
USA, 3 Rocky Mountain Taste and Smell Center Aurora, CO, USA,
4
Afferent Pharmaceuticals San Mateo, CA, USA
ATP is believed to be a crucial neurotransmitter for
communicating gustatory information to nerve fibers. Evidence
is based largely on recordings from mice lacking both P2X2
and P2X3 purinergic receptor subunits (P2X2-P2X3 DKO
mice), which lack responses to all taste stimuli (Finger et al.,
2005). These data suggest that all taste qualities require ATP to
communicate with nerve fibers. However, subsequent studies
have detected ATP release only from Type II taste cells, those
that respond to bitter, sweet, and umami stimuli (Huang et
al., 2007; Romanov et al., 2007). Recent experiments on the
P2X2-P2X3 DKO mice have shown that in addition to the lack
of postsynaptic receptors, these mice fail to release ATP to taste
stimuli (Huang et al., 2011). Thus, the lack of taste responses
may be due to the lack of ATP release rather than the lack of
postsynaptic receptors. To resolve whether postsynaptic P2X
receptors are required for transmission of all tastes to the nervous
system, we have used a pharmacological approach to chemically
block the purinergic receptors while recording from the chorda
tympani nerve in response to a battery of taste stimuli. C57Bl6
mice were injected ip with 6 mg/kg AF-353, a membrane
permeant compound that blocks all P2X3-containing receptors
(P2X3 homotrimers and P2X2/3 heterotrimers; Gever et al.,
2010). Within 15 min of injection, integrated responses to all
It is generally accepted that Type II cells transduce bitter,
sweet, and umami stimuli in rodent taste buds. Recent studies
also demonstrate that Type II taste cells release ATP, a
neurotransmitter believed to play an important role in taste
transduction. However, no classical synapses have been found
to be associated with Type II cells. Are there other contacts
between Type II cells and Type III cells or Type II cells and
nerve processes? In the present study, we utilized conventional
transmission electron microscopy to examine the ultastructural
features of nonsynaptic contacts in rat circumvallate taste buds.
Our results indicate that Type II cells are in intimate contact with
Type III cells in taste buds. Two types of nonsynaptic contacts,
subsurface cisternae of endoplasmic reticulum and/or atypical
mitochondria, have been found to be present adjacent to the
cytoplasmic leaflet of Type II cells at close appositions with
nerve processes. Frequently we observed subsurface cisternae of
smooth or rough endoplasmic reticulum in Type II cells at sites
of apposition with nerve processes. Occasionally we observed
atypical mitochondria and subsurface cisternae adjacent to
each other in Type II cells. We also observed electron-dense
periodic pillars connecting the subsurface cisternae or the
atypical mitochondria to the membranes of Type II cells at
close appositions with nerve processes. We speculate that these
structures are involved in communication between Type II cells
and nerve processes. Acknowledgements: This work is supported
by NIH grants DC00285 and P30 DC04657
POSTER PRESENTATIONS
Abstracts are printed as submitted by the author(s).
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