Abstracts - Association for Chemoreception Sciences

#P78 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Sensory Afferents from the Stomach of the Rat Converge
onto Taste-responsive Neurons in the Rat Brainstem
Alexander J. Denman-Brice, Patricia M. Di Lorenzo
Binghamton University/Psychology Binghamton, NY, USA
Recent descriptions of taste receptors in the gut have set the stage
for the idea that taste stimuli continue to provide information
even when they are no longer in the mouth. For example,
intraduodenal infusions of bitter tastants can modify eating
behavior within a single meal. Given that both taste and postlingual
chemosensory feedback may be important for modifying
eating behavior on a relatively short timescale, it is possible
that chemosensory afferents from the gut may converge onto
the same relay nuclei as taste information in the brainstem.
We investigated the responsiveness of single neurons in the rat
brainstem to tongue and gastric taste stimulation. Initially, rats
were anesthetized with urethane and prepared for recording from
the brainstem. A length of polyethylene tubing was threaded
down the rat’s esophagus to the stomach for delivery of tastants.
A tungsten microelectrode was then placed in the nucleus of
the solitary tract (NTS) and taste-responsive cells were isolated.
Preliminary data from 18 taste-responsive cells show that some
(n=8) NTS cells change their firing rate in response to infusion
of small amounts (0.4 ml) of taste stimuli (0.1 M NaCl, 0.01 M
HCl, 0.01 M quinine, 0.5 M sucrose and 0.1 M MSG) into the
stomach. Gastric responses were most frequently found to NaCl
and MSG; no excitatory responses were found to HCl infused
into the stomach. An additional cell was not responsive to
lingual taste stimuli but was inhibited by gastric tastant delivery
of MSG, HCl and quinine. Collectively, these data suggest that
information from both lingual and post-lingual chemoreceptors
converge onto NTS cells, suggesting a role for post-lingual
chemoreceptors in modulation of ingestive behavior on a short
timescale. Acknowledgements: Supported by NIDCD grant
RO1DC006914 to PMD.
#P79 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Synaptic Properties of the Basolateral Amygdala Projection
to Gustatory Cortex
Melissa Haley 1,2 , Alfredo Fontanini 1,2 , Arianna Maffei 1,2
1
Department of Neurobiology and Behavior Stony Brook, NY, USA,
2
Program in Neuroscience Stony Brook, NY, USA
The gustatory cortex (GC) receives a dense and anatomically
well documented projection from the basolateral nucleus of the
amygdala (BLA). This input is thought to convey affective and
anticipatory information regarding taste. Indeed inactivation
of BLA results in dramatic changes in the way taste and
anticipatory cues are processed in GC. Although the behavioral
and functional significance of this projection has been the focus
of extensive investigation in awake and anesthetized animals,
the synaptic properties and organization of these inputs are
unknown. To study the BLA to GC synapse, viral vectors
carrying a construct for ChannelRhodopsin2 were injected in
the BLA. After 2 weeks, whole-cell recordings in dysgranular
and agranular GC were performed in combination with
photoactivation of BLA terminal fields. BLA afferents were
found to target both excitatory and inhibitory neurons in all
layers of GC. Across all layers, approximately 60% of regularspiking
(RS), fast-spiking (FS), and low-threshold spiking (LTS)
neurons responded to light-activation of BLA afferents. RS cells
had a longer rise time than FS cells (p=.016) and a longer decay
time than FS cells (p=.0004). In addition, differences could be
seen in the synaptic properties of BLA inputs onto neurons in
superficial and deep layers of GC. Layer 2/3 RS cells had larger
current amplitudes than layer 5/6 cells (p=.03), and there was a
significant difference in the percentage of FS cells that responded
to stimulation in layer 2/3 (75%) and layer 5/6 (25%). These data
suggest that BLA inputs in GC have cell type specific and layer
specific properties. The combination of feed-forward inhibition
and excitation likely serves to shape the temporal dynamics of
taste responses and to enhance the representation of behaviorally
salient stimuli. Acknowledgements: National Eye Institute Grant
#R01-EY019885-S1 and National Institute on Deafness and
Other Communication Disorders Grant #R01-DC010389
#P80 POSTER SESSION II:
OLFACTION DEVELOPMENT; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Cortical modulation of taste-related orofacial behaviors
Jennifer X. Li, Donald B. Katz
Brandeis University Waltham, MA, USA
Upon receiving a taste stimulus, primates and rodents produce a
sequence of rhythmic orofacial movements, also known as taste
reactivity (TR), specific elements of which reflect the hedonic
quality (i. e., the palatability) of the stimulus. Aversive stimuli,
such as quinine, elicit bouts of gapes, movements that serve to
eject the stimulus from the mouth. The production of gapes
indicates aversiveness, and the latency to gape is inversely related
to the degree of aversiveness (Travers and Norgren, 1986). While
the motor circuits necessary for taste-related orofacial movements
are contained within a brainstem network (Grill & Norgren), in
the intact animal, this network is modulated by feedback from
higher-order forebrain structures. Relatively little is known about
forebrain structures’ roles in the selection and production of
TR, however. We set out to examine the relationship between
TR and neural responses in primary gustatory cortex (GC) by
performing paired recordings of single unit activity and jaw
electromyography (EMG) in awake rats presented with strong
(0.3 M) and weak (0.03 M) sucrose, and strong (0.001 M) and
weak (0.0001 M) quinine, via intra-oral cannulae. Comparisons
of the time courses of neural and EMG responses revealed that
palatability-related signals in GC preceded those in EMG by
~250 ms, suggesting that GC could drive palatability-related
orofacial movements. Preliminary analyses further demonstrated
that the spiking activity of individual GC neurons was correlated
POSTER PRESENTATIONS
Abstracts are printed as submitted by the author(s).
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