2009 Abstracts - Association for Chemoreception Sciences

including the olfactory epithelium, olfactory bulbs and the medialamygdala. These results are the first step towards showing that T.gondii cysts directly influence the olfactory system leading to analtered behavioral response to predator odors.#P27 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsSexual dimorphism in olfactory bulb structureWilli Bennegger 1 , Elke Weiler 21Maria-von-Linden-Schule, Heckentalstraße 86 D-89518Heidenheim, Germany, 2 Faculty of Medicine, Institute ofPhysiology, Department of Neurophysiology, Ruhr-UniversityD-44780 Bochum, GermanySexual dimorphism in mammals is often observed in the accessoryolfactory system, however, this system is rudimentary in speciessuch as the American mink. Thus, we were interested, if sexdependentstructural differences exist in the main olfactorysystem. Olfactory bulbs of adult American minks color-variety“standard” (Neovison vison var. atratus) were processedhistologically and always the right bulb analyzed with amorphometric system using weight/volume correction factors.The olfactory bulb is significantly bigger in males (152mm 3 )compared to females (107mm 3 ), however, females are muchsmaller than males and so is their absolute brain weight (m 11.51g;f 8.43g). Thus, the bulb-portion on the whole brain is similar(m 1.37%; f 1.32%). On the other hand, the brain relative to thebody mass is much bigger in females (0.85%) compared to males(0.55%), resulting in significantly different bulb/body ratios (m0.0076%; f 0.0112%). Sex-dependent differences exist also in theproportion of the neuronal layers: In males, the olfactory filacomprise the major portion of all layers (26.9%) but only 17.7%in females, where the majors are granule cell (GCL 28.8%) andexternal plexiform layer (EPL 22.8%) overwhelming theproportions in males (GCL 21.7%; EPL 19.2%) significantly.The mitral cell layer is significantly thicker in males (4.7%) thanfemales (3.5%).This indicates that the fila layer is related more tooverall body size (increase in the olfactory sheet / axon numbers)whereas the information processing GCL and EPL is related tothe brain size. This suggests also, that information processing ismuch more complex in females and to sustain the extended GCLthere might be a higher neurogenesis. Therefore, a significantsexual dimorphism in the main olfactory bulb exists, notreported before.#P28 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsHeterogeneous Sensory Innervation of IndividualNecklace GlomeruliRenee E. Cockerham, Adam C. Puche, Steven D. MungerDepartment of Anatomy and Neurobiology, University ofMaryland School of Medicine Baltimore, MD, USAThe mammalian nose employs several olfactory subsystems torecognize and transduce diverse chemosensory stimuli. Thesesubsystems differ in their anatomical position within the nasalcavity, their targets in the olfactory forebrain, and thetransduction mechanisms they employ. Here we report thatthey can also differ in the strategies they use for stimulus coding.Necklace glomeruli are the sole main olfactory bulb (MOB)targets of an olfactory sensory neuron (OSN) subpopulationdistinguished by its expression of the receptor guanylylcyclase GC-D and the phosphodiesterase PDE2, and by itschemosensitivity to the natriuretic peptides uroguanylin andguanylin and the gas CO 2 . In stark contrast to the homogeneoussensory innervation of canonical MOB glomeruli from OSNsexpressing the same odorant receptor (OR), we find that eachnecklace glomerulus of the mouse receives heterogeneousinnervation from at least two distinct sensory neuron populations:one expressing GC-D and PDE2, the other expressing olfactorymarker protein (OMP). In the main olfactory system it is thoughtthat odor identity is encoded by a combinatorial strategy andrepresented in the MOB by a pattern of glomerular activation.This combinatorial coding scheme requires functionallyhomogeneous sensory inputs to individual glomeruli byOSNs expressing the same OR and displaying uniform stimulusselectivity; thus, activity in each glomerulus reflects thestimulation of a single OSN type. The heterogeneous sensoryinnervation of individual necklace glomeruli by multiple,functionally distinct, OSN subtypes precludes a similarcombinatorial coding strategy in this olfactory subsystem.Instead it suggests that the necklace glomeruli could serve ascoincidence detectors for multiple chemosensory stimuli.#P29 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsSpatial analysis of olfactory bulb activity in the sea lampreyWarren W Green 1 , Sana Ahmed 1 , Dominique Derjean 2 ,Réjean Dubuc 2 , Barbara S Zielinski 11Department of Biological Sciences, University of WindsorWindsor, ON, Canada, 2 Centre de Recherche en SciencesNeurologiques, Département de physiologie, Université deMontréal Montréal, QC, CanadaThe sea lamprey (Petromyzon marinus) uses olfaction todetect a variety of odours that induce movement and searchingbehaviours. The peripheral olfactory organ of sea lamprey iscomprised of the main olfactory epithelium (MOE) and theaccessory olfactory organ (AOO). Neural connections from theAOO project solely to the medial region of the olfactory bulb(OB) while projections from the MOE are distributed to allglomerular regions. Our goal is to examine odour input specificityand processing in the OB of sea lamprey as it relates to behaviour.To that effect, we examined the morphological characteristics ofthe MOE and AOO as well as the organization of odourprocessing in the OB. The peripheral olfactory organ ofmetamorphic, parasitic, and migratory adult lamprey wasdissected, sectioned, and the relative area of the MOE andAOO was calculated. The proportion of AOO in the peripheralolfactory organ increased from 22% in metamorphic lamprey toupwards of 30% in parasitic and migratory adult sea lampreyindicating an increase in input from the AOO to the OB duringadult life stages. Additionally, multi-unit action potentials inresponse to odours were recorded in the OB of the live ex vivobrain of parasitic and migratory adult sea lampreys. Actionpotential frequency increased in the medial OB in response to bileacids and the lamprey pheromone 3KPZS. Action potentialfrequency also increased in the lateral and ventral-lateral OB inresponse to basic amino acids and 3KPZS, respectively. Theseresults indicate that odour input and processing in the medialOB is important for responding to behaviourally-relevant odours.Funding provided by the GLFC and NSERC.P O S T E R SAbstracts | 35