2009 Abstracts - Association for Chemoreception Sciences

#P30 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsSpatial Representations of Natural Odor Objects Acrossthe Glomerular Layer of the Rat Olfactory BulbBrett A. Johnson, Joan Ong, Michael LeonDept. of Neurobiology & Behavior, UC Irvine Irvine, CA, USAWe previously have determined glomerular responses to 365monomolecular odorants, using uptake of 2-deoxyglucose toquantitatively assess activity across the entire rat olfactory bulb.To determine how these response patterns compare to responsesevoked by more natural odor stimuli, we now have mappeduptake during exposures to vapors arising from a variety ofobjects that might be important to rodents in the wild. Sixteendistinct stimuli ranging from possible food sources such as fruits,vegetables, and meats to environmental objects such as grass,herbs, and tree leaves were chopped or homogenized and thentheir vapors introduced into an air stream in the same manner aswe used previously for pure odorant chemicals. The natural odorobjects evoked robust and surprisingly focal patterns of 2-deoxyglucose uptake that in some cases were closely related topatterns evoked by known major monomolecular componentsthat are represented in our archive, but that in other cases weremore simple than might have been predicted given the multiplicityof components that must have been present in the vapors. Thesedata suggest the possibility of important mixture responseinteractions and provide a foundation for understanding theneural coding of natural odor stimuli.#P31 Poster session I: Chemosensory disorders, modelsand aging/Central chemosensory circuitsAnalysis of responses to musk odorants in olfactory sensoryneurons and in the main olfactory bulbMika Shirasu, Kazushige TouharaDepartment of Integrated Biosciences, The University of TokyoChiba, JapanMusk odorants are widely utilized in various perfumes because oftheir fascinating aminalic note. They exhibit similar odorcharacters despite their different chemical structures such asmacrocyclic, nitro and polycyclic moieties. To elucidate themechanism of musk odor perception, we investigated the responsepatterns of mouse olfactory sensory neurons (OSNs) and themain olfactory bulb (MOB) to musk odorants. In Ca 2+ imaging,68 neurons out of ~3000 dissociated OSNs responded to eugenol,whereas only 4 neurons responded to muscone, one ofmacrocyclic musk odorants. We next examined responses to muskodorants in the MOB using OMP-spH mice. No responsiveglomerulus was found in the dorsal and lateral regions of MOB.Then, we performed unilateral bulbectomy to image responses inthe medial region of MOB. This surgical technique enabled us toobserve a large part of the medial region of MOB, the area thathad not been imaged previously. Interestingly, only a fewglomeruli in the medial region showed responses to muscone.The muscone-responsive glomeruli did not respond to nitromusks, polycyclic musks and other classes of odorants such asaldehydes, acetates and benzenoid compounds. Using c-Fosexpression as a marker for odor-induced neuronal activity in theglomerular layer of the MOB, we analyzed spatial patterns of c-Fos positive glomeruli that were stimulated with musk odorants.c-Fos induction by muscone was observed around only a fewglomeruli that were located in a region very similar to thoseobtained by the bulbar imaging. Our findings indicate thatmuscone appears to be recognized by a few narrowly-tuned ORsand muscone activates a few glomeruli in the restricted region ofthe medial MOB in mice.#P32 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsInput Driven Synchrony of Oscillating OlfactoryReceptor Neurons: A Computational Modeling StudyIl Park 1 , Yuriy V. Bobkov 2 , Kirill Ukhanov 2 , Barry W. Ache 2,3 ,Jose C. Principe 11Department of Biomedical Engineering, University of FloridaGainesville, FL, USA, 2 Whitney Laboratory, Center for Smelland Taste, and McKnight Brain Institute, University of FloridaGainesville, FL, USA, 3 Departments of Zoology and NeuroscienceGainesville, FL, USATemporally structured activity in bursting and/or oscillatingneurons can be utilized to embed the temporal structure ofsensory input into an instantaneous population code. Wehypothesize that spontaneously bursting olfactory receptorneurons (ORNs) reported earlier by our group can extracttemporal features of the odor signal. We showed that, at least inlobster, each such ORN responds to a narrow range of stimulusfrequencies based on their spontaneous bursting discharge andphase dependent response to odor stimulation. A heterogeneouspopulation of such ORNs could encode a wide spectrum ofstimulus intermittency and also increase the reliability ofencoding. Computational model based on a modified renewalprocess was extrapolated from experimental recordings fromsingle lobster ORNs, and used to generate population responsesto a stimulation pattern. Simulation and analytical methods wereused to obtain the probability of various temporal patterns ofresponse. A homogeneous population showed synchronizationdynamics which changed in a stimulus frequency dependentmanner and could be enhanced, maintained, or depressed. In theabsence of stimulation, the population quickly approached theasymptotic pattern. To test if the heterogeneous population couldactually encode stimulus intermittency, a neural decoder was builtusing machine learning. We suggest a biologically plausible neuraldecoder based on a simple integrating neuron.#P33 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsIncrease in Number of Androgen Receptor ImmunoreactiveCells in the Medial Amygdala of Male Hamsters in Responseto Chemosensory InputCamille B Blake, Michael MeredithFlorida State University, Department of Biological Science,Program in Neuroscience Tallahassee, FL, USAIn many species, including hamsters, mating behavior isdependent on integration of chemosensory and hormonal cues.Chemosensory stimuli are detected by vomeronasal system,which projects to many regions that contain steroid receptors,including the medial amygdala (Me). Sexual behavior is alsofacilitated in male hamsters by direct action of testosterone withinthe medial amygdala. Me can be subdivided into anterior (MeA)36 | AChemS Abstracts 2009