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that it responds specifically and in a concentration-dependent
manner to inositol, an essential nutrient for
B. mori.
The selectivity
of BmGr8 responses is consistent with the known responses of one
of the gustatory receptor neurons in the lateral styloconic sensilla of
this species. Insect gustatory receptors are predicted to have seven-
transmembrane domains. They are distantly related to insect
olfactory receptors, which have an inverted topology compared
with G-protein coupled receptors. We have now determined that the
transmembrane topology of BmGr8 is the same as that of insect
olfactory receptors and different from that of mammalian olfactory
and gustatory receptors. We also found that an orphan receptor
from the ‘bitter’ receptor subfamily, BmGr53, has the same
topology as BmGr8. This is the first time that the topology of any
insect gustatory receptor has been determined. Zhang, H. J.;
Anderson, A. R.; Trowell, S. C.; Luo, A. R.; Xiang, Z. H.;
Xia, Q. Y., Topological and functional characterization of an
insect gustatory receptor. PLoS One 2011, 6(8): e24111.
Acknowledgements: “This work was supported by a grant from the
the National Natural Science Foundation of China (30972147), the
Ministry of Education of the People’s Republic of China Program
for Changjiang Scholars and Innovative Research Team in
University (No. IRT0750), CSIRO and the Doctoral Innovation
Fund of Southwest University (kb2008002).
#P243
WITHDRAWN
#P244
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Taste representations in the lateral hypothalamus
emphasize palatability
Jennifer X. Li, Takashi Yoshida, Donald B. Katz
Brandeis University Waltham, MA, USA
The lateral hypothalamus (LH) is known to be critically involved
in regulating feeding behavior (Boyle, 1975). Because our desire
to eat is affected by how our food tastes, and because LH is
extensively interconnected with canonical regions of the gustatory
circuit (Lei, 2008; Cho, 2003), LH is likely to participate in taste
processing, especially regarding palatability. We characterized the
taste response properties of LH neurons via single-unit recordings
in awake rats during the delivery of a pseudo-randomized sequence
of five tastants: 300 mM sucrose, 150 mM sodium chloride, water,
10 mM citric acid, and 2 mM quinine hydrochloride, which range
from highly palatable to unpalatable. Out of a total of 128 neurons,
47% (n=60) produced statistically distinguishable responses
(p<0.01, ANOVA) to different tastants. A closer examination of the
time course of the taste responses of these 60 neurons revealed a
succession of epochs that reflect separate qualities of the tastant, a
dynamic representation of the sensory experience reminiscent of
what has been observed elsewhere in the gustatory circuit,
including in the insular cortex (Katz, 2001) and the basolateral
amygdala (Fontanini, 2009). Unlike the other two regions,
however, LH neurons proceed through only two epochs—initial
responses signaled the non-specific presence of a tastant on the
tongue, and subsequent firing encoded the palatability of said
tastant. Finally, palatable and unpalatable tastants preferentially
activate non-overlapping LH subpopulations with distinct
dynamics: palatable tastants reliably evoked much more transient
responses than unpalatable tastants. We conclude that the lateral
hypothalamus is a dedicated region for processing palatability, but
that its role may differ for palatable versus unpalatable stimuli.
Acknowledgements: R01 DC7703 and T32 NS007292
#P245
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Dietary exposure to sucrose solutions alters taste-mediated
licking for sweeteners, but not taste-evoked neural responses
of the NST in mice
Stuart A McCaughey
1
, Rotsen Rocha
2
, Tiffany Lambert
2
,
John I Glendinning
2
1
Center for Medical Education, Ball State University Muncie, IN,
USA,
2
Department of Biology, Barnard College, Columbia
University New York, NY, USA
Following dietary exposure to sugar solutions, most strains of
mice exhibit increased intake of and preference for sweeteners.
In addition, some (e.g., 129) but not all (e.g., C57BL/6) strains of
mice exhibit increased motivation to obtain sugar solutions. The
neurobiological bases of these exposure-induced changes in sugar
responsiveness are poorly understood. We asked whether they are
mediated (at least in part) by enhanced orosensory responsiveness.
In Experiment 1, we examined short-term licking responses of two
mouse strains (129X1/SvJ [129] and C57BL/6 [B6]) to two
solutions (0.5 M sucrose and 19 mM saccharin) following 3 days of
exposure to a diet supplemented with 0.5 M sucrose solution
(experimental) or water alone (control). There was no effect of diet
treatment on the rate at which the mice licked for the sweetened
solutions. However, there was a significant effect of exposure type
on the number of 5 s trials initiated during the 30 min test sessions.
The experimental 129 mice initiated significantly more trials than
controls for both sweetener solutions, whereas the experimental B6
mice initiated significantly fewer trials than controls. In Experiment
2, we asked whether these behavioral changes were associated with
altered perception of sweet taste intensity. To this end, we
compared taste-evoked multi-unit responses of the nucleus of the
solitary tract (NST) to the sweetener solutions across experimental
and control mice. There was a significant effect of mouse strain,
but not of dietary exposure regime, on taste-evoked NST responses
to sucrose. This indicates that the exposure-induced changes in
licking for sweeteners were not mediated by changes in early taste
processing. Instead, they may reflect altered central reward
pathways in the ventral forebrain.
108 | AChemS Abstracts 2012
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