Abstracts - Association for Chemoreception Sciences

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P O S T E R S #P51 POSTER SESSION I: TASTE IMAGING & PSYCHOPHYSICS; CENTRAL TASTE; MULTIPLE MODALITIES; CENTRAL & PERIPHERAL OLFACTION Heterotrimeric G-protein bg subunits in the Mouse Olfactory Epithelium Aaron S. Sathyanesan, Adrian Feijoo, Abhinav Parikh, Julie Wolf, Weihong Lin University of Maryland Baltimore County Baltimore, MD, USA G-protein coupled signaling cascades are involved in a variety of activities in olfactory sensory neurons (OSNs), such as odor transduction and axonal projection. While the roles of heterotrimeric G-protein a-subunits, such as G aolf are well documented, relatively very little is known about Gbg subunits in OSNs. However, recent studies in other research fields have yielded a surge of data documenting the diverse functions of Gbg subunits. Here we investigate the expression of all known G-protein bg subunits in the olfactory epithelium of mice using reverse transcriptase PCR (RT-PCR) analysis. Our data confirmed the expression of G-protein b1, g8 and g13 in the mouse olfactory epithelium found previously by other investigators. Additionally, we found the presence of four of the seven known g subunits (g2, g3, g5 and g12) and three of the five known b subunits (b2, b4 and b5) in the olfactory epithelium. Further, we have used RNA In situ Hybridization (RISH) to study the expression of these Gbg subunits. We have so far confirmed in RISH analysis that mRNA transcripts of b4, g2, g5 and g12 subunits are present in the olfactory epithelium. We have also observed positive labeling of these subunit mRNAs in the VNO as well as in the septal organ. Our results demonstrate that multiple Gbg subunits are expressed in olfactory sensory epithelia. Acknowledgements: Supported by NIH/NIDCD DC009269 to WL. #P52 POSTER SESSION II: OLFACTORY PHYSIOLOGY & CELL BIOLOGY; TASTE MOLECULAR GENETICS; CHEMESTHESIS & TRIGEMINAL Odor fear conditioning effects on piriform cortical odor processing in awake rats Chien-Fu F. Chen 1,2 , Donald A. Wilson 1,2,3 1 EBI, NKI Orangeburg, NY, USA, 2 University of Oklahoma Norman, OK, USA, 3 NYU Medical School New York, NY, USA Odors that we encounter everyday are usually very complex. While the olfactory system is capable of discriminating complex yet similar odors (e.g. mocha and latte) with practice, the underlying mechanisms are not clear. As more data have been reported in anesthetized animals, data from awake animals are few. This experiment was therefore designed to investigate two related questions in awake rats: 1) odor coding of complex mixture in the anterior piriform cortex (aPCX) and 2) fear conditioning effects on odor coding in the aPCX. To record activity from awake animals, Long-Evans hooded rats were chronically implanted with movable bundles of microwires aimed at the aPCX. Up to 7 units were recorded simultaneously, and the electrode bundle was moved over time to sample additional cells. Odor-shock conditioning was performed to induce odor-related aversive experience on the rats, with a complex 10-odorant mixture as the conditioned stimulus (CS). The CS odor, along with overlapping odor mixtures and limonene were presented to the animals before the conditioning trials and for several days post-training. The results (n = 206 units) showed a slight decrease in percentage of units that showed excitation after conditioning, and a significant increase in suppression. A significant decrease in average spontaneous activity was observed after conditioning. Finally, an analysis of single-unit responsiveness revealed a late suppressive response after conditioning to all three mixtures overlapping with the CS but not limonene. Interestingly, while responsiveness to control odors decreased after conditioning, responses to the CS became temporally focused, with a more narrow range of onset and offset latencies. Together, odor fear conditioning should enhance signal:noise and CS coding acuity in aPCX. Acknowledgements: NIDCD to DAW #P53 POSTER SESSION II: OLFACTORY PHYSIOLOGY & CELL BIOLOGY; TASTE MOLECULAR GENETICS; CHEMESTHESIS & TRIGEMINAL Physiological Roles of MOB CCKergic Neurons Shaolin Liu, Michael T. Shipley Department of Anatomy & Neurobiology, Program in Neuroscience, University of Maryland School of Medicine Baltimore, MD, USA Axons from olfactory sensory neurons (OSN) expressing the same odorant receptor target a pair of glomeruli on the lateral and medial sides of each olfactory bulb (OB). These two “mirror glomeruli” are inter-connected via an intra-bulbar association (IA) system, which predominantly arises from superficial and middle tufted cells in the external plexiform layer (EPL). These IA cells: (1) exclusively contain CCK, indicating this peptide as their major or co-neurotransmitter; (2) have primary dendrites extending into glomerular layer where each glomerulus is surrounded by numerous juxtaglomerular (JG) cells. The vast majority of JG cells are GABAergic periglomerular (PG) and short axon (SA) cells; (3) have axons projecting to the contralateral internal plexiform layer (IPL) and synapsing onto the dendrites of local granule cells. Thus, these CCKergic IA cells are well suited to modulate both glomerular inhibitory circuits engaged by GABAergic PG cells and infraglomerular inhibitory circuits involving granule cells and mitral cells. We tested this hypothesis and found that: (1) CCK enhanced sIPSCs in ET and PG/SA cells and presynaptic inhibition of ON terminals by depolarizing and increasing GABA release from PG/SA cells via CCK-2 receptors. This suggests that CCK enhances intraglomerular inhibition of mitral/tufted cells and thus regulates sensory processing in glomeruli. (2) CCK enhanced sIPSCs in mitral cells. This could be due to the enhancement of the glomerular inhibition or the infraglomerular inhibition or both. Both possibilities are under investigation. In summary, our findings support the hypothesis that the CCKergic superficial/middle tufted cells shape the OB output to the olfactory cortex by modulating intraglomerular and possibly infraglomerular inhibitory circuits. Acknowledgements: Supported by NIH NIDCD DC005676 44 | AChemS Abstracts 2010 Abstracts are printed as submitted by the author(s)
#P54 POSTER SESSION II: OLFACTORY PHYSIOLOGY & CELL BIOLOGY; TASTE MOLECULAR GENETICS; CHEMESTHESIS & TRIGEMINAL Mitral Cell Responses to Sensory Input Under Tonic Inhibition Zuoyi Shao, Adam C. Puche, Michael T. Shipley Department of Anatomy & Neurobiology, Program in Neuroscience, University of Maryland School of Medicine Baltimore, MD, USA Olfactory signals are initially processed in glomeruli, where olfactory nerve (ON) axons form excitatory synapses onto principal output neurons, mitral/tufted (MT) cells. MT cells are generally thought to be regulated mainly by inhibition at their lateral dendrites from GABAergic granule cells (GC). Less is known about inhibition occurring at their glomerular tuft by GABAergic periglomerular (PG) cells. We recently reported that the intrinsic bursting of ET cells results in strong spontaneous activation of most GABAergic PG cells to produce tonic presynaptic inhibition of ON terminals (Shao et al 2009). Since MT cells receive IPSCs from PG cells in response to ON input, we hypothesized that MT cells may also receive tonic postsynaptic inhibition. To test this hypothesis we measured spontaneous IPSC frequency in MT cells before and after restricted intraglomerular puff of gabazine (GBZ). GBZ significantly reduced the rate of sIPSCs and dramatically increased spontaneous spiking in MT cells. This indicates that tonic inhibition is of glomerular origin and potently regulates MT cell firing. To determine if tonic intraglomerular postsynaptic inhibition is due to ET cell drive of PG cells, we puffed L/T type calcium channel blockers into the glomerulus to block spontaneous ET cell bursting (Liu and Shipley 2008). As predicted, this significantly reduced spontaneous IPSCs in MT cells. These results, taken with our previous findings show that MT cell responses to ON sensory input are strongly regulated by tonic pre- and postsynaptic inhibition mediated by the ET-PG-MT cell circuit. Tonic intraglomerular pre- and postsynaptic inhibition may operate to set the gain and offset of the glomerular input-output function. Acknowledgements: Supported by NIDCD DC005676 #P55 POSTER SESSION II: OLFACTORY PHYSIOLOGY & CELL BIOLOGY; TASTE MOLECULAR GENETICS; CHEMESTHESIS & TRIGEMINAL Ethanol Reduces Olfactory Bulb Output by Reducing Excitatory Drive to Mitral/Tufted Cells Feras Jeradeh-Boursoulian, Abdallah Hayar Univ. of Arkansas for Medical Sciences Little Rock, AR, USA In alcoholics, the smell of ethanol may be an important determinant of its acceptance because the drug’s reinforcing properties could be associated with its chemosensory attributes. Moreover, it is possible that chronic alcohol abuse could make ethanol smell and taste better. While the effects of ethanol have been extensively investigated in many brain circuits, its effects on neuronal processing within the olfactory bulb are still unknown. In this study, we have used extracellular and whole-cell patchclamp recordings in olfactory bulb slices to determine the acute effects of ethanol on output neurons of the olfactory bulb. Mitral and tufted cells appeared to be more responsive to ethanol application (50-100 mM) than external tufted cells. The most prominent effect of ethanol was a decrease in the amplitude and frequency of spontaneous EPSCs. Moreover, olfactory nerveevoked EPSCs exhibited a decrease in amplitude and electric charge. These effects of ethanol persisted in the presence of the GABA-A receptor blocker, gabazine, but were attenuated in the presence of the NMDA receptor blocker, APV. Extracellular recordings revealed that ethanol decreased the firing frequency and the number of spikes per burst in most mitral and tufted cells. In the olfactory bulb, NMDA receptors have been implicated in synaptic plasticity, dendro-dendritic inhibition, self-excitation, and glutamate spillover. The attenuation of NMDA receptor activity by ethanol is therefore expected to reduce neuronal interactions and as a consequence attenuate olfactory bulb synchronous output activity in response to odor stimulation. This study provides insight into the mechanisms by which ethanol exposure could modulate olfactory bulb neuronal interactions, which may lead to an alteration in the sensory perception of ethanol odor. Acknowledgements: PHS grants: DC007123, DC007876, RR020146. #P56 POSTER SESSION II: OLFACTORY PHYSIOLOGY & CELL BIOLOGY; TASTE MOLECULAR GENETICS; CHEMESTHESIS & TRIGEMINAL Lateral interactions in the in vivo olfactory bulb network of the rat show heterogeneous distance dependences and vary strongly with respect to respiratory phase Matthew E Phillips 1,2 , Gordon M Shepherd 1 , David C Willhite 1 1 Yale University School of Medicine, Department of Neurobiology New Haven, CT, USA, 2 Yale University, Department of Physics New Haven, CT, USA The lateral connectivity of inhibitory granule cells in the mammalian olfactory bulb (OB) was previously shown to be sparse and distributed using viral tracers (Willhite et al. 2006). However, electrophysiological evidence of this distribution has not previously been shown in the in vivo network. To investigate this possible network organization we performed intracellular recordings of Mitral cells (MC) in vivo paired with focal electrical stimulations of the caudal olfactory nerve layer (ONL). This preparation allows for the activation of distant posterior (hypothetical “surround”) glomeruli while avoiding presynaptic stimulation of the recorded cell (hypothetical “center”). Evoked inhibitory post-synaptic potentials (IPSPs) were recorded in MCs in response to posterior electrical ONL stimulations at varying distances from the recording location. IPSP amplitudes showed a heterogeneous distribution as a function of the distance between the stimulus and recording locations. This result suggests that the lateral network of the OB is not organized in a classical centersurround, distance dependent manner. However, there was a general tendency for more distant ONL stimuli to evoke smaller amplitude IPSPs than proximal stimuli. But, stimulus location alone could not predict the evoked IPSP amplitude – for example, the distance dependence nature could vary as a function of the stimulating current. The evoked IPSP amplitudes depended strongly on when the ONL stimulation was triggered with respect to the respiratory phase of the freely breathing animal. Taken together, these results imply that the OB network is highly distributed – within which there is a weak center-surround distance dependence as a function of stimulus strength relative to the respiratory phase. P O S T E R S Abstracts are printed as submitted by the author(s) Abstracts | 45
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Page 37 and 38: TGI. The present study investigated
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#P204 POSTER SESSION IV: CHEMOSENSO
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familiarity and cultural difference
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#P265 is found on page 128. #P266 P
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perception of purine 5’-ribonucle
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#P278 POSTER SESSION VI: PERIPHERAL
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(CT), the greater superficial petro
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were significantly different from o
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MSG on NaCl is evidently highlighte
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consisting of motors and IFT comple
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wing. Philip Callahan exposed insec
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seem to indicate that total nasal v
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possibly suggesting non-apoptotic m
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#P325 POSTER SESSION VII: OLFACTORY
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of 7/10, and causing eyes to water
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showed that N1/P2 latencies were lo
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differentiated patients with AD (M=
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pleasantness 3)of mixtures (A,B), A
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Index Aarts, H - P328 Abe, K - P88,
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Haase, L - P3, P4, P29, P355 Haddad
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Murata, Y - P272 Murphy, C - P3, P4
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Veldhuizen, M - P7, P24, P25, P242,
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Registration 7:30 am to 1:00 pm, 6:
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See you next year! AChemS 33rd Annu
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Abstracts - Association for Chemoreception Sciences

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