Abstracts - Association for Chemoreception Sciences

#51 SYMPOSIUM:
EXPERIENCE DRIVEN PLASTICITY
OF THE OLFACTORY SYSTEM
#53 SYMPOSIUM:
EXPERIENCE DRIVEN PLASTICITY
OF THE OLFACTORY SYSTEM
Understanding Plasticity in the Olfactory Intrabulbar Map
Leonardo Belluscio
National Institutes of Health / NINDS Bethesda, MD, USA
In the mammalian olfactory system sensory neurons project
their axons to the surface in the olfactory bulb generating a
pair of glomerular maps that reflect odorant receptor identity.
These maps are further connected through a set of reciprocal
intrabulbar projections that are mediated by tufted cells that
specifically link iso-functional odor columns to produce a second
order map called the intrabulbar map. We have shown that
intrabulbar projections are established postnatally and undergo
continuously refinement through an activity dependent process
that has no critical period. Here we present that both loss of
olfactory sensory input and broad odorant stimulation are
capable of disrupting the intrabulbar map specificity, while
re-introduction of normal activity restores the map to proper
order. We also reveal that the regenerating interneurons
are central to intrabulbar circuit plasticity and that proper
connectivity depends specifically upon new neurons from
the rostral migratory stream. Together these data illustrate
that olfactory bulb plasticity is a balance between activity,
regeneration and remodeling. Acknowledgements: National
Institute of Neurological Disorders and Stroke, Intramural
Research Program.
#52 SYMPOSIUM:
EXPERIENCE DRIVEN PLASTICITY
OF THE OLFACTORY SYSTEM
Long-term imaging of odor representations in awake mice
Takaki Komiyama
University of California, San Diego, CNCB, La Jolla CA 92093 USA
How are sensory representations in the brain influenced by the
state of an animal? Here we use chronic two-photon calcium
imaging to explore how wakefulness and experience shape odor
representations in the mouse olfactory bulb. Comparing the
awake and anesthetized state, we show that wakefulness greatly
enhances the activity of inhibitory granule cells and makes
principal mitral cell odor responses more sparse and temporally
dynamic. In awake mice, brief repeated odor experience leads
to a gradual and long-lasting (months) weakening of mitral cell
odor representations. This mitral cell plasticity is odor specific,
recovers gradually over months, and can be repeated with
different odors. Furthermore, the expression of this experiencedependent
plasticity is prevented by anesthesia. Together, our
results demonstrate the dynamic nature of mitral cell odor
representations in awake animals, which is constantly shaped by
recent odor experience.
Olfactory Experience Shapes Insect Olfactory Centres
Jean-Marc Devaud
Research Center on Animal Cognition, Université Paul Sabatier
Toulouse, France
Insects provide excellent models to study how neural
networks dedicated to olfactory processing are formed during
development, and how they work in the adult. However, their
organisation is not fixed once development is achieved.
On the contrary, as in vertebrates, the connectivity and functional
organisation of insect olfactory systems are not fixed: they
exhibit clear plastic properties, as shown in various species over
the recent years. In our work, we have been focusing on the
plastic changes affecting the anatomy of the olfactory centres as
a consequence of olfactory experience, be it the mere exposure
to environmental odorants or associative learning and memory.
In particular, we have been looking for structural rearrangements
in two main olfactory centres known for their role in olfactory
learning and memory in the insect brain: the antennal lobes and
the mushroom bodies. The modular organization of these two
neuropils allows quantifying the changes affecting their structure
in the brains of animals submitted to different treatments.
By doing so, and by focusing mostly on the honeybee (Apis
mellifera) as a model species, we have been able to show that
the formation of long-term memories of previous olfactory
experience is associated with structural modifications in insect
olfactory networks. Interestingly, such modifications vary with
the nature of the experience undergone by the animal, and
may be considered as supports of olfactory memories. Thus,
they are likely to contribute to the acquisition and retention of
behavioural responses adapted to changing environments.
#53.5 CLINICAL LUNCHEON:
TASTE RECEPTORS IN GUT AND PANCREAS
REGULATE ENDOCRINE FUNCTION
Robert F. Margolskee
Monell Chemical Senses Center, Philadelphia, PA, USA
Many of the receptors and downstream signalling proteins
involved in taste detection and transduction are expressed also
in intestinal and pancreatic endocrine cells where they underlie
certain chemosensory responses. Intestinal endocrine cells
express T1r taste receptors, the taste G-protein gustducin, and
several other taste transduction elements. So too do pancreatic
islet endocrine cells. Knockout mice lacking alpha-gustducin
or the sweet taste receptor subunit T1r3 have deficiencies in
intestinal secretion of glucagon-like peptide-1 (GLP-1) and in
the regulation of plasma levels of insulin and glucose. Glucosedependent
insulin release from mouse pancreatic islets ex vivo
is stimulated by sucralose and other sweeteners. Islets from T1r3
knockout mice release insulin normally in response to glucose,
but show no enhanced release of insulin in response to noncaloric
sweeteners. Thus, there appear to be two mechanisms
ORAL ABSTRACTS
Abstracts are printed as submitted by the author(s).
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