Abstracts - Association for Chemoreception Sciences

(CT), the greater superficial petrosal (GSP) and the
glossopharyngeal (IX). These three nerves all undergo a
progressive decrease in terminal field volumes throughout
postnatal development, leading to decreases in overlapping fields.
We propose that competitive interactions between the three
nerves shape terminal field development. To examine the effects of
removal of competition from GSP and IX on CT terminal field
development, the GSP and IX nerves were sectioned at postnatal
day 15 (P15), P25 or P65, representing different stages of terminal
field maturation. The terminal field volume of the CT nerve was
then assessed 35 days following nerve section. Using an
anterograde tracer coupled with confocal microscopy, we found
that the CT terminal field volume was five times larger than agematched
controls. This finding was consistent regardless of age of
GSP and IX section. We confirmed that there were no changes in
taste responses from the CT nerve. The absence of cytokeratin-
19-like immunoreactivity in the foliate papillae and in the
nasoincisor duct was used to confirm the lack of IX and GSP
reinnervation, respectively. Following bilateral GSP and IX
section at P65, no behavioral changes were seen in brief-access
taste testing responses to a concentration series of NaCl or
quinine. These studies highlight the remarkable plasticity of the
central gustatory system and provide a basis for future, more
mechanistic studies of gustatory competition.
Acknowledgements: Supported by NIH Grants R01 DC00407
and R01 DC006938
#P285 POSTER SESSION VI:
PERIPHERAL AND CENTRAL TASTE;
PERIPHERAL OLFACTION
Analysis of functional and anatomical relationships between
trigeminal inferior alveolar afferents and gustatory neurons
within the nucleus of the solitary tract
Yves Boucher 1,2 , Fawzia Zerari 2,3 , Adeline Braud 1,2
1
UFR Odontologie, Université Denis Diderot Paris, France,
2
CRicm UMRS 975 Paris, France, 3 UFR Biologie, Université
Denis Diderot Paris, France
#P286 POSTER SESSION VI:
PERIPHERAL AND CENTRAL TASTE;
PERIPHERAL OLFACTION
Repeated Peripheral Nerve Injury Leads to Enhanced
Growth of Terminal Fields in the Nucleus of the Solitary
Tract of Adult Rat
Rebecca Reddaway, David L. Hill
University of Virginia Charlottesville, VA, USA
Unilateral transection of the chorda tympani nerve (CTX) leads to
long-term changes in the peripheral and central taste systems of
adult rats. Most notably, there is a loss of about 50% of the CT
terminal field volume in the nucleus of the solitary tract (NTS).
We found that the injury-induced decrease of CT nerve terminal
field volume is not due to cell death and degeneration of central
processes, but rather a failure in regeneration of all peripheral
processes. Accordingly, the significant reduction of volume
occupied by the CT nerve terminal field following CTX may lead
to the expansion of intact neighboring nerve terminal fields. The
current experiment assessed long-term reorganization of the intact
glossopharyngeal (IX) and greater superficial petrosal (GSP) nerve
terminal fields following CTX in adult rats. To examine this
potential reorganization, we fluorescently labeled the regenerated
CT and the GSP and IX nerves 60 days post-CTX and then
examined the terminal field organization of these three nerves in
the rostral NTS. Unexpectedly, the terminal field volumes of all
nerves, including the CT, were greater than controls. This
unforeseen increase in CT terminal field indicates that a
conditioning lesion effect occurred. That is, the initial CTX served
as a conditioning lesion that when followed by triple nerve label,
which requires the transection of all three nerves, leads to the
rapid expansion of the CT nerve terminal field. It is unclear if the
expansion of IX and GSP terminal fields is related to CTX and the
subsequent loss of CT terminal field or if this reorganization
occurs in the 48 hours following triple labeling along with the
rapid expansion of CT terminal field. Acknowledgements:
Supported by NIH Grants R01 DC00407 and R01 DC006938
P O S T E R S
Since a recent clinical study revealed an increase in taste
thresholds with dental deafferentation (Boucher et al., 2006), we
wanted to investigate the biological basis of this phenomenon. We
explored trigeminal inferior alveolar nerve (IAN) innervating
mandibular teeth and gustatory interactions within the nucleus of
the solitary tract (NST) of rats. We recorded single unit tastantevoked
responses of NST neurons before and after IAN electrical
stimulation. Electrical IAN stimulation eliciting a short latency
jaw opening reflex resulted in a significant decrease in gustatory
NST neuron responses. We furthermore used a double-label
strategy with c-Fos mapping of chorda tympani (CT) activated
NST gustatory neurons coupled to an anterograde labeling of
IAN afferents. We observed labelled IAN boutons “en passant”
apposed to CT activated neurons in the gustatory NST. With a
complementary triple-label approach using retrograde labelling of
solitary-parabrachial neurons coupled to anterograde labelling of
gustatory CT and trigeminal afferents, we evidenced NST second
order gustatory neurons apposed by CT and IAN afferents.
Taken together, our results provide an anatomical and functional
basis to support trigeminal dental and gustatory interactions in
the brainstem. ref: Boucher Y, Berteretche MV, Farhang F, Arvy
MP, Azérad J, Faurion A. taste deficits related to dental
deafferentation: an electrogustometric study in humans. eur j oral
sci. 2006;114(6):456-64 Acknowledgements: IFRO
#P287 POSTER SESSION VI:
PERIPHERAL AND CENTRAL TASTE;
PERIPHERAL OLFACTION
Amino acid taste-evoked activity in the parabrachial
nucleus of mice
John D Boughter, Kenichi Tokita
University of Tennessee Health Science Center Memphis, TN,
USA
Objective: The parabrachial nucleus (PBN) is a key interface
between medullary and forebrain gustatory areas in rodents. We
investigated responses to basic tastants as well as umami-tasting
stimuli, including MSG, IMP, and L-type amino acids, in the PBN
using both in vivo physiology and taste-evoked c-Fos IHC
techniques. We also examined Fos expression in PBN neurons
that project to the lateral hypothalamus (LH), an area involved in
feeding, via retrograde tracing. Methods: Taste-evoked responses
in the PBN of C57BL/6J inbred mice were recorded with in vivo
single-unit recording techniques. For Fos studies, injections of the
retrograde tracer Fluorogold were made bilaterally into the LH.
Several days later, mice were stimulated intraorally with MSG,
IMP, MSG+IMP, sucrose or water. Mice were perfused 2 h later,
and brain sections through the PBN were processed for FG and
c-Fos IHC. Results: Preliminary analysis of 10 recorded PBN
Abstracts are printed as submitted by the author(s)
Abstracts | 121