1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

45 Poster Peripheral Olfaction and Peripheral TasteBURSTING WITH ODOR: INTRINSICALLY OSCILLATINGOLFACTORY RECEPTOR NEURONSAche B.W. 1 , Bobkov Y.V. 1 1 Whitney Laboratory for Marine Bioscienceand Center for Smell and Taste, University of Florida, St. Augustine, FLPacemaker and/or intrinsically oscillating neurons are fundamental toneuronal network function but generally have not been considered in thecontext of primary sensory signaling. Here, we report a novelsubpopulation of lobster primary olfactory receptor neurons (ORNs)that exhibit spontaneous, rhythmic bursts of action potentials between0.02 to 0.9 bursts/sec. The bursting is intrinsic: the structure of thebursts and the inherent frequency of bursting are consistent for anygiven cell, bursting is sensitive to membrane potential and Ca 2+ , andpharmacological treatement presumably targeting HCN channels thatfrequently underlie neural oscillations (ZD7288, 200M) disruptsbursting. The ORNs can be entrained by odorants. Odorants transientlyapplied to the cells evoke bursts similar to the spontaneous bursts inphase-dependent manner. The efficacy of entrainment is concentrationdependent: more intense stimuli cause the cell to discharge earlier in thecycle. Synchronization of the bursting ORN ensemble by periodicstimulus acquisition such as sniffing would effectively enhance thedetection and amplification of weak signals, generally assumed to beone of the hallmarks of olfaction. Supported by the NIDCD throughDC001655.46 Poster Peripheral Olfaction and Peripheral TasteUSE OF CILIARY BEAT FREQUENCY FOR MEASURINGCHEMORESPONSE IN PARAMECIUMBell W.E. 1 , Hallworth R.J. 2 , Wyatt T.A. 3 , Sisson J.H. 3 1 Biology,Virginia Military Institute, Lexington, VA; 2 Biomedical Sciences,Creighton University, Omaha, NE; 3 Internal Medicine, University ofNebraska Medical Center, Omaha, NESwimming behavior in Paramecium is dependant on the directionand frequency of ciliary beating. When Paramecium encounter achemoattractant, the membrane hyperpolarizes and ciliary beatfrequency increases, while the frequency of action potentials decreases.Chemorepellants cause a depolarization and can increase the frequencyand/or duration of action potentials that cause a reversal of ciliary beat.Chemoresponse in Paramecium is measured by population-based assayssuch as the T-Maze or the capillary tube assay or by scoring thebehavior of individual cells in backward-swimming or avoidancereaction tests. Analog videotape has been analyzed by various means toquantify swimming speed and turning or to measure ciliary beatfrequency (CBF). We have utilized a novel digital analysis system toaccurately quantify CBF in immobilized Paramecium. This systemyields data similar to analog systems at beat frequencies less than 15 hz,but is significantly more accurate at faster beat rates (Sisson et. al2002). This digital system also reduces data analysis time from hours tominutes. Our immobilization method, adherence to coverslips using abiological adhesive, resulted in low mortality and CBF in unstimulatedcells similar to that collected by analog video analysis. When cells wereexposed to the chemoattractant molecules acetate and ammonia, CBFincreased significantly. Hyperpolarizing the membrane by reducingexternal potassium ion concentration also increased CBF, as expected.Acetate concentrations that caused measurable changes in CBF aresimilar to the minimal concentrations required to detect populationbasedattraction in T-Maze assays.47 Poster Peripheral Olfaction and Peripheral TasteIMPLANTABLE NEURAL INTERFACES FORCHARACTERIZING POPULATION RESPONSES TOODORANTS AND ELECTRICAL STIMULI IN THE NURSESHARK, GINGLYMOSTOMA CIRRATUMLehmkuhle M.J. 1 , Vetter R.J. 2 , Parikh H. 1 , Carrier J.C. 3 , Kipke D.R. 11 Biomedical Engineering, University of Michigan, Ann Arbor, MI;2 NeuroNexus Technologies, Inc., Ann Arbor, MI; 3 Biology, AlbionCollege, Albion, MIThe objective of this study is to develop short- and long-termimplantable neural interfaces within the central nervous system ofsharks. Nurse sharks were wild-caught in the Florida Keys and kept inholding facilities at Albion College. Animals were placed in a customstereotaxic tank and anesthetized with MS-222 (Sigma,100 mg/kg) inartificial seawater (Instant Ocean, Aquarium Systems, Inc.), the gillscontinuously perfused. A surgical access of ~5 cm by ~2.5 cm wasmade to expose the right olfactory rosette, bulb, tract, and lobe.Following surgical access, animals were paralyzed (pancuroniumbromide, 0.9 mg/kg, IM in elasmobranch ringer´s), anesthesia removed,and vital signs monitored. Two arrays of 16 microelectrodes wereplaced in the olfactory bulb and lobe, and two Ag|AgCl electrodesplaced within the olfactory rosette through the inlet naris. Single-unitand local field potential (LFP) activity was recorded in the olfactorylobe. The median single-unit spontaneous activity in the lobe was 0.4imp/s in the awake animal. Electrical stimulation (monophasic, bipolar,300 µA) of the seawater space within the rosette produced electricallydrivenLFP and single-unit spike activity in the olfactory lobe with alatency of 300–450 msec. A five channel odorant delivery system willallow us to characterize odorant responses simultaneously in theolfactory bulb and lobe. Support provided by DARPA Bio-inspiredundersea sensors program HR0011-05-C-0018.48 Poster Peripheral Olfaction and Peripheral TasteRESPONSES OF SPONTANEOUSLY INACTIVE OLFACTORYRECEPTOR NEURONS CORRELATE WITH EOG IN BLACKBULLHEAD CATFISH (AMEIURUS MELAS)Dolensek J. 1 , Valentincic T. 1 1 Biology, University of Ljubljana,Ljubljana, SloveniaWe investigated electrophysiological responses of the olfactory organof black bullhead catfish to amino acids in water with low ionconcentrations (R>10 6 Ωcm). Prior to stimulation, olfactory receptorneurons (ORNs) were either spontaneously active or inactive. Inprevious studies, single spontaneously active ORNs' responses to aminoacids were unpredictable over successive tests and did not correlate withthe relative magnitude of the EOG response. In the present study, thenumber of spontaneously inactive ORNs responding to amino acidscorrelated highly with the amplitude of EOG (Pearson R = 0.9, p