Page 55 - ACHEMS 2012 PROGRAM

#P83 POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Periodic stimulation affects odor representations in
antennal lobe of the moth Manduca sexta
Benjamin Houot 1, Samuel Bradley1, Shreejoy Tripathy1,2,
Erich M. Staudacher1, Kevin C. Daly1
1Department of Biology, West Virginia University Morgantown,
WV, USA, 2 Center for the Neural Basis of Cognition,
Carnegie Mellon University Pittsburgh, PA, USA
Odor representations vary as a function of the context in which
they are experienced. Wing beating affects the interaction of the
insect antennae with odor molecules by inducing a periodic
structure as well as periodic changes of air velocity across the
antennae that may affect receptor cell responses. We have recently
established that both antenna and antennal lobe (AL) track
periodically structured stimuli independent of odor presence or
identity. Furthermore, behavioral studies of odor detection suggest
that the rate of false positive responses drops when stimuli are
presented as pulse trains. The goal of this study was to determine if
pulsed odor affects the separation of odor representations in the AL.
We used 16 channel electrode arrays to make multiunit and multi
local field potential (LFP) recordings to monitor AL responses to
olfactory stimuli pulsed at 20 and 25 Hz (wing beat frequency
range). We presented a homologous series of five undiluted
alcohols and ketones. Power spectral analysis indicated that 23%
of the units pulse tracked across odors. Interestingly, odors with
longer carbon-chain-lengths induced significantly higher pulse
tracking. Next, we varied the durations of the three stimuli
(continuous, 10 and 20 Hz) from 500 ms to 3 s for two odors and a
blank. LFPs appear to be stimulus duration dependent suggesting a
ramping up of oscillations over time. Futhermore, we will use
Euclidean analysis to quantify representational distance as
a function of pulsing versus continuous stimulation. Our results
suggest that neural odor representations are context dependent at
the AL level. Acknowledgements: This study is supported by NIH
R01-DC009417 to KCD
#P84 POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Nitric Oxide Differentially Affects the Excitability of
Subsets of Cultured Local Neurons from the Manduca Sexta
Antennal Lobe
Michael A Miller, Mark R Higgins, Alan J Nighorn
Department of Neuroscience University of Arizona
Tucson, AZ, USA
Nitric oxide (NO) modulates olfactory information processing via
multiple molecular pathways. Local neurons in the antennal lobe
exist in subsets that have been traditionally described based on
morphology and current profiles and only a modest population of
LNs are immunoreactive to soluble guanalyl cyclase(sGC),
the best characterized target for NO. Subsets of local neurons are
differentially affected by the presence of NO, implying that
modulation of ion channels may vary between the subsets of LNs.
To examine the effects of NO on LNs, electrically evoked
responses were monitored using whole cell voltage clamping of
cultured AL neurons. We have begun to examine the specific ion
currents affected by NO and the molecular mechanisms by which
those currents are affected. We found that different subsets of
LNs were either hyperpolarized, depolarized or unaffected in the
presence of NO. Different currents were affected in these subsets
and they also showed differential responses to exogenous
cGMP application. These results suggest that there are multiple
molecular targets for NO and these targets vary among the
different subsets of LNs.
#P85 POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Mechanisms of calcium-mediated excitation and plasticity in
primary olfactory pathways of the honey bee
Danielle T. Protas, Carsten Duch, Brian H. Smith
School of Life Sciences, Arizona State University Tempe, AZ, USA
Spatiotemporal processing in the mammalian and invertebrate
olfactory systems is subject to plasticity driven by biogenic amines.
We study this processing using honey bees, which have been
extensively studied with respect to nonassociative, associative and
operant based olfactory learning and memory. Octopamine is the
invertebrate analog to epinephrine, and it is an important factor in
driving associative plasticity in the honey bee antennal lobes (ALs).
More recently we started to test hypotheses related to how
octopamine might be involved in synaptic organization in the AL
circuitry. Octopamine acts via different receptor subtypes, and one
specific subtype (AmOA1) gates calcium release from intracellular
stores. Calcium also enters AL interneurons via acetylcholine
(ACh) receptors, which are driven by ACh release from sensory
neuron terminals, as well as through voltage gated calcium
channels (VGCCs). We propose that the confluence of the
conditioned and unconditioned stimuli occurs via calcium release
from these independent sources. We employ 2-photon excitation
(2PE) microscopy using fluorescent calcium indicators to
investigate the potential sources of calcium in projection neuron
(PN) dendrites in vivo. PN dendrites within glomeruli in the honey
bee AL show calcium increase in response to odor stimulation.
Octopamine causes amplified calcium transients when applied prior
to olfactory stimuli. We have shown direct activation of nACh
receptors upon application of nicotine. The response persists
despite cadmium chloride application, a VGCC antagonist,
suggesting a direct postsynaptic activation. Our studies will allow
for a greater understanding of plasticity in the primary olfactory
neuropil of the honey bee and may generalize to an understanding
of plasticity in the mammalian olfactory bulb. Acknowledgements:
NIH-NIDCD and Office of Naval Research
#P86 POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Pulse tracking of antennal lobe neurons is enhanced by input
from the thoracic ganglia in Manduca sexta
Erich M. Staudacher1, Regina Tiede2, Joachim Schachtner2,
Kevin C. Daly1
1Dept. Biology, West Virginia University Morgantown, WV, USA,
2FB Biologie, Philipps-Universität Marburg, Germany
Natural olfactory stimuli are series of short, discrete events,
because odor plumes are filamentous. Moreover, the stimulus is
structured by wing beating, which should be reflected by the neural
response. Antennal lobe (AL) output neurons, which were recorded
intracellularly in isolated head preparations in Manduca sexta,
showed pulse tracking limited to 10–15 Hz. In intact moths ~7-25%
Abstracts | 55
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