1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

253 Poster Central Olfaction and Chemical EcologyIONIC MECHANISMS REGULATING INTRINSIC BURSTINGIN MOUSE OLFACTORY BULB EXTERNAL TUFTED CELLSLiu S. 1 , Shipley M.T. 1 1 Anatomy and Neurobiology, University ofMaryland at Baltimore, Baltimore, MDExternal tufted (ET) cells in olfactory bulb glomeruli receivemonosynaptic olfactory nerve (ON) input and excite periglomerular andshort axon cells thus forming the basic glomerular local circuit. ET cellsexhibit spontaneous bursting at the range of frequency (1-8 Hz) whichspans the range of rodent sniffing frequencies. Thus ET cellsspontaneously drive the glomerular circuit in a range of frequenciesideally matched to the periodic sampling of odorant stimuli. ET cellbursting is mediated by intrinsic conductances. A persistent Na + current(I NaP ) active near resting membrane potential is required for burstgeneration but the mechanisms that regulate the duration of a burst, itstermination and the inter-burst interval are unknown. The threshold foraction potentials in mouse ET cells is ~-44 mV. When the membrane isdepolarized to intermediate levels (~ -38 mV) a Ca 2+ spike is generated.NiCl 2 (1 mM) and NNC55-0396 (50 µM), a selective T-type calciumchannel blocker, completely abolished this low-voltage activatedcalcium spike and Ca 2+ current. We hypothesized that activation of T-type Ca 2+ channels might activate Ca 2+ -activated K current, whichterminates bursts by re-polarizing the membrane. Consistent with this,ET cells exhibit large-conductance calcium-dependent potassium (BK)currents which were blocked by iberiotoxin (IBTX, 200 nM), a selectiveBK channel blocker. Furthermore, IBTX significantly broadens theevoked burst duration. These results support the hypothesis that the T-type calcium channel plays a critical role in the burst firing activity ofET cells by activating BK channels, which contribute to the terminationof the burst. Supported by NIH NIDCD DC 36940 & DC 02173.254 Poster Central Olfaction and Chemical EcologyBINARAL INTERACTION MODULATES OLFACTORY BULBRESPONSES TO ODORANT HISTORYSinger B. 1 , Kim S. 2 , Zochowski M. 2 1 Neuroscience Graduate Program,University of Michigan, Ann Arbor, MI; 2 Department of Physics,University of Michigan, Ann Arbor, MIWhile odorant-evoked oscillations in the vertebrate olfactory bulbhave been studied extensively, information about which neural circuitsgenerate and modulate them has been missing. In particular, it is unclearto what extent oscillations are a product of the olfactory bulb alone, or ifthey reflect coactivation of the olfactory bulb and other central odorprocessingregions. Using voltage-sensitive dye imaging, we show thatpaired-pulse odorant presentations with interstimulus intervals of 2-5 shad dramatic and diverse effects on the DC depolarization andoscillations that occur in the turtle olfactory bulb. If the same odorant ispresented on each pulse, the DC depolarization is depressed while thepower of the low-latency 14 Hz oscillation is enhanced in response tothe second stimulation. If different odorants are presented on the firstand second pulse, then all components of the response are depressed.These effects are present if both pulses are delivered to the same naris,or if the first pulse is delivered contralaterally to the second. Thesimilarity of uninaral and binaral effects suggest that the historydependentmodulation of the olfactory bulb response is mediated bybrain structures sending bilateral projections to both olfactory bulbs.This work was supported by a UM Research Incentives Grant (M.Z.).B.H.S is supported by NIH T32-GM007863 and T32-DC00011.255 Poster Central Olfaction and Chemical EcologyMULTI-SINGLE UNIT AND LOCAL FIELD OSCILLATORYDYNAMICS FROM IN-VIVO BRAIN STIMULATIONFOCUSED ON PARALLEL CONNECTIONS BETWEEN THEANTERIOR AND POSTERIOR PIRIFORM CORTICES ANDTHE ENTORHINAL CORTEXHermer-Vazquez R. 1 , Hermer-Vazquez L. 1 1 Psychology, University ofFlorida, Gainesville, FLA major question in neuroscience concerns the computationaladvantages of parallel processing in the brain. The olfactory-limbiccircuitry contains multiple examples of parallel inputs from multipleareas onto a single upstream center. The current study was undertakento determine the neural correlates of olfactory information flow betweentwo output sites in the piriform to the medial entorhinal cortex. Thisposter focuses on stage 1 of these ongoing experiments, conducted inthe anesthetized preparation. Our prior results from recordingsimultaneously from multiple nodes within the olfactory-motor circuitduring a GO/NO-GO olfactory task found the importance of transientfrequency modulation and spike inhibitory activity in predicting trialoutcome. Our hypothesis states that specific frequency bands from thetato gamma facilitate both the transfer of an artificial stimulus pulse or astimulus odor, in a site-specific manner, from the posterior and anteriorpiriform to distinct laminar layers of the medial entorhinal cortex. Weused grid microelectrode wires for anterior and posterior piriformstimulation and vertical silicon multisite electrodes for recording currentsources in the entorhinal cortex layers. Results currently indicate wehave detected layer-specific long lasting complex waveforms generatedby one or both piriform sites to the entorhinal, with distinct frequencydepedendent modulation. These results will aid in characterizing howthe flow of information from the periphery, influences feedfowarddynamics as exemplified by the parallel inputs from the piriform to theentorhinal cortices.256 Poster Central Olfaction and Chemical EcologyNEUROMODULATORY ROLE FOR POST-SYNAPTICDENSITY 95 (PSD-95) IN THE OLFACTORY BULBMarks D.R. 1 , Fadool D. 2 1 Neuroscience, Florida State University,Tallahassee, FL; 2 Biological Science, Neuroscience, and MolecularBiophysics, Florida State University, Tallahassee, FLPrevious work by our laboratory has demonstrated a pivotal role forthe voltage-gated Shaker potassium channel (Kv1.3) highly expressedin the olfactory bulb (OB) in acuity, threshold, and odorantdiscrimination. The insulin receptor (IR) kinase and the adaptor protein,PSD-95, are expressed at high levels in the OB whereby PSD-95disrupts insulin-evoked Kv1.3 current suppression in an activitydependantmanner. We now show that all three proteins are co-localizedin the OB, with PSD-95 showing heavy labeling across all neurolaminaincluding the glomeruli. We found that PSD-95 coimmunoiprecipitateswith Kv1.3 as well as the IR kinase, demonstrating a multiple proteinproteininteraction. PSD-95 clusters Kv1.3 in HEK293 cells, as well asclusters the IR kinase, but only in the presence of Kv1.3. A PSD-95mutant lacking the SH 3 and guanylate kinase (GK) domain (PSD-95SH 3 ) was constructed, as well as use of previous mutants created by A.El-Husseini (2002) to dissect the interaction of these three proteins.PSD-95 PM (palmitoylation) was also used to demonstrate that PSD-95may be involved in the trafficking and distribution of Kv1.3. Wepropose a model of interaction of Kv1.3, IR kinase, and PSD-95 whereKv1.3 channels are bound by PDZ domains 1 & 2 of PSD-95 and the IRkinase is bound by the SH 3 domain. These data demonstrate that PSD-95 may influence the excitability of synaptic connections in the OB viaK channel interaction and subsequent modulation. Supported by NIHDC03387 (NIDCD).64