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of the extracellularly recorded units tracked pulsed odors up to 30
Hz. Furthermore, a pair of identified histaminergic neurons, which
arborize bilaterally in presumed motor and/or premotor centers of
the mesothoracic ganglion, terminates in both ALs. Thus, our
working hypothesis is, that intact connections between the brain
and the ventral nerve cord are necessary for pulse tracking at wing
beat frequencies. We developed a new preparation to test this
hypothesis. Legs and wings were removed and the thorax opened to
expose the thoracic ganglia and the neck connectives. Brain and
ALs were exposed for intracellular recording and staining. A blank
and two monomolecular odors, 2-hexanone and 1-hexanol
(undiluted and 10 µg/2µl), were presented as 3 s pulse trains. Nine
frequencies from 10 and 40 Hz were used at 50% duty cycle. Inter
stimulus interval was 10 s. Using power spectral density analysis,
we show, for the first time in moth, that projection neurons and
local interneurons follow pulsed stimuli up to 25 Hz, some even to
40 Hz. About 25 % of all tested AL neurons tracked pulsed stimuli;
in some cases, tracking depended on odor identity. This suggests,
that AL neurons only can represent the temporal structure of natural
stimuli when the connections between brain and thoracic ganglia
are intact. Currently, we test how modifying the functionality of the
brain to ventral nerve cord connections affects pulse tracking.
Acknowledgements: This work was supported by NIH grant
NIH-DC009417 to KCD and DFG grant SCHA 678/3-3 to JS.
#P218
POSTER SESSION II:
TRIGEMINAL SYSTEM; TASTE CNS;
NEUROIMAGING; OLFACTION CNS
Inhibiting DNA methyltransferases during discrimination
conditioning impairs recall of the conditioned olfactory
associations in honey bees (
Apis mellifera
)
Christina M. Burden
1
, Gro V. Amdam
1,2
, Brian H. Smith
1
1
Arizona State University Tempe, AZ, USA,
2
Norwegian University
of Life Sciences Aas, Norway
De novo
DNA methylation plays a key role in memory
consolidation.
1,2
We asked how it affects olfactory memories by
blocking DNA methyltransferase 3 (Dnmt3) activity in honey bees
(
Apis mellifera
). Previous work established that Dnmt3 inhibition
impairs consolidation of simple associative olfactory memories in
bees.
3
We assessed how Dnmt3 inhibition affects recall of olfactory
memories following discrimination conditioning, which allowed us
to simultaneously assess the role of DNA methylation in associative
and nonassociative memories. We injected adult bees with 0.17 μg
RG108 (Dnmt inhibitor) or saline. Then, we trained them to
discriminate a rewarded odor from an unrewarded odor (1-hexanol
and 2-octanone). We assessed learning and short-term memory by
monitoring the conditioning trials. After 96-hours, we assessed
long-term memory with a series of extinction trials. Acquisition of
the conditioned responses was not affected by RG108, indicating
that
de novo
DNA methylation may not be involved in learning and
short-term memory. However, RG108 did impair performance
during extinction trials. RG108-treated bees were less likely to
respond to the first trial of the rewarded odor and exhibited a faster
extinction of the response to the rewarded odor across the rest of
the trials. The probability of a response to the unrewarded odor
extinction trials was equal between the treatment groups. These
data indicate that DNA methylation-dependent processes mediate
consolidation of associative olfactory memories. In contrast,
consolidation of the nonassociative memories (unrewarded odor)
may not depend on DNA methylation.
REFERENCES
1. Miller,
C.A., et al. Nature Neuroscience, 2010. 13(6): 664-6. 2. Miller,
C.A. and J.D. Sweatt. Neuron, 2007. 53: 857-869. 3. Lockett, G.A.,
et al. NeuroReport, 2010. 21(12): 812-6.
Acknowledgements: This
study was supported by funding from NIH NIDCD (BHS), Office
of Naval Research (BHS), PEW Charitable Trust (GVA), and the
Research Council of Norway (180504)(GVA)
#P87
POSTER SESSION III:
OLFACTION DEVELOPMENT & CNS;
HUMAN PSYCHOPHYSICS; TASTE PERIPHERY
The Role of Primary Cilia in the Regenerative Properties of
Olfactory Basal Stem Cells
Ariell M. Joiner, Jeremy C. McIntyre, Jeffrey R. Martens
Department of Pharmacology, University of Michigan Ann
Arbor, MI, USA
The olfactory epithelium (OE) is one of the few neuronal tissues to
undergo constitutive neurogenesis throughout the lifespan of an
organism. The OE is composed of differentiated olfactory sensory
neurons (OSNs) and supporting cells, and two populations of basal
precursors, globose basal cells (GBCs) and horizontal basal cells
(HBCs). While GBCs frequently divide and differentiate into OSNs
and supporting cells to restore the OE, HBCs are more quiescent
yet able to restore the OE following severe insult. There is growing
evidence that primary cilia play roles in cell proliferation and
differentiation. In the OE, immunohistochemical (IHC) analysis of
Arl13b (a cilia-localized protein) revealed that in addition to being
expressed in olfactory cilia of OSNs, Arl13b-labeled primary cilia
are on basal cells of the OE. Co-labeling with the HBC markers
CD54 (I-CAM1) and p63 showed that Arl13b-labeled cilia are
found on HBCs. We therefore hypothesized that primary cilia on
HBCs regulate their cell fate. To test this hypothesis, we used the
Oak Ridge Polycystic Kidney (ORPK) mouse, which contains a
hypomorphic mutation in
ift88
, resulting in depletion of IFT88
(a protein important for ciliogenesis and cilia maintenance) and
partial loss of cilia. IHC analysis of ORPK mice revealed a
predicted reduction of cilia in the HBC population (p63+ cells)
compared to wild-type. Surprisingly, through our staining of the
ORPK OE, we uncovered a prominent change in the location of
HBCs; whereas in wild-type animals HBCs are restricted to the
basal-most region of the OE by P19, HBCs in ORPK animals of the
same age are also present in more apical regions of the OE. These
data suggest that cilia may be critical for HBC turnover and
olfactory tissue maintenance. Acknowledgements: R01DC009606
(to J.R.M.) T32DC00011 (to A.M.J.)
#P88
POSTER SESSION III:
OLFACTION DEVELOPMENT & CNS;
HUMAN PSYCHOPHYSICS; TASTE PERIPHERY
Role of Neogenin in Olfactory Epithelium Development
Joseph W.K. Kam
1,2
, David da Dilva
1,2
, Jean-Francois Cloutier
1,2
1
Montreal Neurological Institue, Department of Neurology and
Neurosurgery Montreal, QC, Canada,
2
McGill University
Montreal, QC, Canada
The birth and differentiation of Olfactory Sensory Neurons (OSNs)
is critical for our ability to detect and decode odorant information
from the environment. To better define the molecular mechanisms
that control neurogenesis in the Olfactory Epithelium (OE),
we have examined the role of the transmembrane protein Neogenin
in olfactory neurogenesis. Neogenin, a member of the
immunoglobulin family, has been implicated in the regulation of
diverse processes during development of the nervous system,
including axonal guidance, cell migration, and cell differentiation.
56 | AChemS Abstracts 2012
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