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Abstracts | 27
in axolotls exposed to GnRH, NPY, or a control treatment (Ringer’s
solution). We also find that multiple genes for both GnRH and NPY
receptors are expressed in the olfactory epithelium, again
suggesting these compounds may have complex effects on odorant
processing. The vertebrate brain actively regulates processing in the
retina and cochlea. Our studies suggest that the brain also regulates
activity in the olfactory epithelium to emphasize stimuli that are
most relevant to the animal’s current behavioral and physiological
state. Acknowledgements: Supported by the National Science
Foundation (IOS 0817785), fellowships from the Marine Biological
Laboratory, and Michigan State University
#56
SYMPOSIUM: MODULATION OF EARLY
OLFACTORY PROCESSING BY INTERNAL
PHYSIOLOGICAL STATES
Metabolic Sensor in
Drosophila
Olfactory Receptor Neurons
Jing W. Wang, Cory M. Root, Kang I. Ko, Andrew K. Shepherd,
Scott A. Lindsay, Steven A. Wasserman
UCSD/Division of Biological Sciences La Jolla, CA, USA
The modulation of behavior by internal physiological states is
essential for animal survival. Like many other animals, hungry
fruit flies exhibit different food searching behaviors. We have
identified key olfactory sensory neurons for innate odor preference
and discovered that nutrient sensors in these neurons play an
important role in appetitive decisions. Our studies indicate that two
neuropeptides short neuropeptide F (sNPF) and tachykinin causes
presynaptic facilitation and inhibition, respectively, in specific
neurons, and the concerted effect controls appetitive behavior in the
fruit fly. Using two-photon calcium imaging, we demonstrate that
starvation-triggered behavioral change is accompanied by dramatic
shifts in the odor map. The neuropeptide sNPF, a homolog of the
mammalian NPY, is highly implicated in hunger signaling and is
expressed in
Drosophila
olfactory sensory neurons (OSNs).
sNPF signaling in DM1 glomerulus is necessary for the starvation-
dependent modulation of both olfactory representation and food
search behavior. Furthermore, the sNPF receptor is expressed in
OSNs and mediates a feedback enhancement of sensory
transmission in DM1. We then investigated starvation modulation
in DM5—a glomerulus that mediates innate aversion behavior.
Starvation suppresses DM5’s sensitivity to odor stimulation, and
that this suppression is mediated by tachykinin signaling.
Furthermore, starvation modulation of DM5 also influences food
search behavior. Thus, early olfactory processing and appetitive
behavior are profoundly controlled by metabolic states in
Drosophila
. Starvation does not simply scale up or down global
activity in the antennal lobe. Rather, it upregulates activity in
certain sensory channels and downregulate it in others towards a
concerted modulation of appetitive behaviors. Acknowledgements:
NIDCD (R01DC009597,1F31DC009511), NIDDK
(R01DK092640).
#57
SYMPOSIUM: MODULATION OF EARLY
OLFACTORY PROCESSING BY INTERNAL
PHYSIOLOGICAL STATES
Neuromodulation of granule cell function in the olfactory bulb
Ricardo C. Araneda
University of Maryland/Biology College Park, MD, USA
The neural network in the olfactory bulb (OB) provides the first
and only synaptic relay in the olfactory pathway to cortex.
Therefore, it plays an important role in olfactory processing.
The activity of neurons in the OB is highly influenced by
modulatory afferent systems that are triggered by behavioral
context. Among these neuromodulatory systems, the noradrenergic
and cholinergic systems play an especially important role in
promoting synaptic changes underlying aspects of olfactory
function such as odor discrimination and learning that are crucial
for the execution of social behaviors. Yet, despite this important
role of noradrenaline and acetylcholine in olfactory information
processing our understanding of the cellular and physiological
mechanisms underlying their actions remains poorly understood.
Recent work from our lab has determined general functional
principles governing neuromodulation by noradrenaline and
acetylcholine of two important components of the OB circuit,
the most prominent inhibitory neuron in the OB, the granule cell
(GCs), and the output neurons (mitral/tufted cells). Our work
indicates that noradrenaline and acetylcholine produce a marked
excitation of GCs and that this excitation is exacerbated by the
activation of a non-selective cationic current. Thus, activation of
these neuromodulatory systems increases the inhibitory input onto
mitral/tufted cells. In contrast, only acetylcholine produces a
marked excitation of output neurons, via two mechanisms,
activation of nicotinic and muscarinic receptors respectively.
Nevertheless, under subthreshold stimulation of these receptors,
inhibition mediated by GCs is predominant. Thus, we conclude that
a major effect of these systems is to increase the inhibition of
output neurons as a result of the increased excitation of GCs.
Acknowledgements: NIDCD R01DC009817
#58
SYMPOSIUM: MODULATION OF EARLY
OLFACTORY PROCESSING BY INTERNAL
PHYSIOLOGICAL STATES
Inhibitory Control of Sensory Input in the Mammalian
Olfactory Bulb
Ron Yu
1,2
, Limei Ma
1
, Qiang Qiu
1
1
Stowers Institute for Medical Research Kansas City, MO, USA,
2
University of Kansas Medical Center Kansas City, KS, USA
Sensory information is transformed at various stages to allow the
parsing and assembly of sensory features. In the mammalian
olfactory system, odor information is first detected by the olfactory
sensory neurons (OSNs) and is relayed to the olfactory bulb
through the OSN axons converging in the olfactory glomeruli.
The glomeruli are considered as the functional units of odor
information processing. In order to study the transformation of
sensory input at the glomerular level, we have developed transgenic
mice that express the genetically encoded Ca
2+
sensor G-CaMP2
in the olfactory sensory neurons. We have imaged the glomerular
response to large panels of odors in live animals in the dorsal
olfactory bulb. We find strong presynaptic inhibition of the
glomerular responses. The inhibition normalizes odor-evoked
responses and its patterns are odor-dependent. Moreover, the
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