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#P217
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Linking sensory input to behavioral output using Drosophila
olfactory system
Vikas Bhandawat, Seung-Hye Jung, Catherine Hueston
Duke University Durham, NC, USA
Olfaction is a crucial modality for many animals, and mediates
behavioral responses to food, mates and predators. Olfaction begins
with odor molecules binding to and activating olfactory receptor
neurons (ORNs). Each ORN expresses a single (or small number of
receptors) out of large family of receptor, which defines its odor
response profile. Most odors activate many ORN-types and
activities in multiple ORN-types are integrated to guide behavior.
In recent years, great progress has been made in understanding odor
processing at the periphery. In contrast, relatively little is known
about the relation between activity in ORN and behavior. This is
largely due to the fact that it is difficult to control odor stimulus in
freely moving animals and without stimulus control it is difficult to
link odor responses to behavior. In this study, we describe a novel
behavioral arena in which a fly’s walking behavior can be
measured under precisely controlled stimulus conditions. We use
this arena in combination with single-cell recording and fly
genetics to ask two fundamental questions in olfaction: 1) What are
changes in a fly’s walking behavior that accompanies its attraction
to odor? and 2) What is the contribution of a single ORN-type in
eliciting odor-evoked behavior? Attraction to an odor can be
decomposed into two parameters: First, the fly dramatically
increases the time it spends inside the odor-zone each time it enters
in. Second, the time it takes for the flies to return to the odor-zone
after it loses the odor also dramatically decreases. Interestingly,
odor induced changes in the two parameters are dependent on the
identity of the odor. Behaviors elicited by activation of a single
ORN-type are dramatically different from those odors that activate
many receptors and will be discussed.
#P218
This abstract has been moved to Poster Session II,
page 54.
#P219
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Histamine Enhances Antennal Lobe Pulse Tracking and
Lowers False Positive Responses in Behavioral Detection
Threshold Tasks in the Moth
Manduca sexta
Rex Burkland, Mitel Patel, Benjamin Houot, Kevin C Daly
West Virginia University/Biology Morgantown, WV, USA
Recent studies show that the antennal lobe (AL) of the moth,
Manduca sexta,
tracks periodically structured stimuli at natural
wing beat frequencies (10-30Hz). Odor detection is also enhanced
when pulsed at these frequencies. This may be mediated by a
bilateral pair of histamine immuno-reactive neurons, which project
from the mesothoracic ganglion to the AL. To characterize the
effect of histamine on behavioral measures of odor detection and
physiological measures of AL responses, we conducted two studies.
First, we measured detection thresholds in the moth,
Manduca
sexta
under control and pharmacologically impaired conditions.
Moths were trained to respond to 2-hexanone; 24 h later, both ALs
were injected with 0.8 nl of saline vehicle, either with or without
drug, then tested (blindly) across a 5 log-step dilution series of
2-hexanone. In separate groups, we injected histamine, or 1 of 2
competitive antagonists, cimetidine or ranitidine. Three dilutions of
each drug were used. Results indicate that histamine blockade
raises odor detection thresholds by significantly increasing false
positive rates, whereas histamine had the opposite effect. Next, we
placed multichannel electrodes into the AL using standard methods
and measured unitary pulse tracking ability before and during
histamine application. Odor was pulsed at 20 Hz. Five 500 ms
pulse trains were presented, each spaced by 10 s; this was repeated
every 2 min. Power spectral density analysis indicated that
histamine significantly increases the pulse tracking ability of AL.
This effect took ~10 min to asymptote. Thus, as pulse tracking
ability is enhanced, the ability to accurately detect the presence of
odor increased. These findings suggest that histamine actively
modulates sensitivity to the temporal structure of stimuli.
Acknowledgements: This work was supported by
NIH-DC009417 to KCD
#P220
POSTER SESSION VI:
OLFACTION CNS; TASTE PERIPHERY &
CNS; MULTIMODAL RECEPTION
Odor attraction behavior of
Drosophila melanogaster
is biased via inhibitory projection neuron activity in the
lateral horn area
Antonia Strutz
1
, Jan Soelter
2
, Veit Grabe
1
, Amelie Baschitz
1
,
Abu Farhan
1
, Jürgen Rybak
1
, Markus Knaden
1
,
Michael Schmuker
2,3
, Bill S. Hansson
1
, Silke Sache
1
1
Max Planck Institute for Chemical Ecology/Evolutionary
Neuroethology Jena, Germany,
2
Free University
Berlin/Neuroinformatics & Theoretical Neuroscience Berlin,
Germany,
3
Bernstein Center for Computational Neuroscience
Berlin, Germany
The olfactory system of the vinegar fly
Drosophila melanogaster
provides an excellent system to study neuronal networks
underlying coding and processing of sensory information. Initially,
olfactory sensory neurons (OSNs) transfer peripheral information
to the antennal lobe (AL), the primary olfactory neuropil. Within
the AL dense synaptic connectivity between OSNs, local
interneurons (LNs) and projection neurons (PNs) results in a
discernible glomerular organization. The glomerular convergence
of OSNs expressing a specific receptor and uniglomerular
innervations of excitatory PNs (ePNs) create odor specific
topographic activity maps in the AL. PNs equal mitral cells of
vertebrates and relay the olfactory information to higher brain
centers as the mushroom body calyx (MB) and the lateral horn
(LH). Whereas a role in olfactory learning processes is assigned for
the MB calyx, the function of the LH is still unclear. In this study
we investigate inhibitory PNs (iPNs, ~45) which develop
polyglomerular innervations within the AL and project exclusively
to the LH. Morphological characterization of these neurons has
been performed using photoactivated GFP, immunostainings with
pre- and postsynaptic markers and reconstruction of 3-dimensional
maps. Functional analysis via calcium imaging revealed several
specific odor response domains in the LH differing in their
characteristic spatial and temporal properties. The domains varied
according to odor concentration as well as identity. Furthermore,
high and low concentrated odors are clearly represented in separate
regions of the LH. Silencing these neurons using RNAi leads to
drastic changes in hedonic valences of odors. This indicates a
crucial role for iPNs in evaluating pleasantness of ecologically
important odors.
100 | AChemS Abstracts 2012
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