1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

49 Poster Peripheral Olfaction and Peripheral TasteCULTURED OLFACTORY RECEPTOR NEURONS SHOWSUMMATION, ADAPTATION, AND AGE-RELATEDDIFFERENCES IN EOG RESPONSE KINETICSViswaprakash N. 1 , Josephson E.M. 1 , Vodyanoy V.J. 2 1 Anatomy,Physiology, and Pharmacology, Auburn University, Auburn, AL;2 Biosensor Laboratory, Auburn University, Auburn, ALWe investigated EOG responses of olfactory receptor neurons inorganotypic olfactory epithelium (OE)-olfactory bulb (OB) cultures. Weexposed cultures to charcoal-filtered air, individual odorants, and amixture of (+) and (-) carvone, eugenol, and ethyl butyrate and recordedEOG potentials. We characterized OMP and β-tubulin expression in thesame cultures with fluorescence immunochemistry. EOG responses ofcultured OE were similar to those of acutely dissected OE. Cultures 3-4days old (n = 8) showed rapid rise times but prolonged decay times.Cultures 13-15 days old (n = 8) showed both rapid rise and decay times.All cultures responded to the four odorants when presented individually,but their responses were variable; ethyl butyrate elicited the strongestresponse on average. At high frequency stimulation with aninterstimulus interval (ISI) of 200 ms, the EOG responses summated.With a longer ISI of 800 ms, adaptation occurred with the second andsucceeding responses of lower amplitude than the first. The responseamplitude only fully recovered when the duration of the ISI reached 20seconds. The cultures contained cells positive for OMP, a marker formature olfactory receptor neurons in situ, and other cells positive for β-tubulin, a protein found in maturing neurons. These results suggest thatOE passes through an immature stage in the week followingexplantation. This likely reflects development of olfactory receptorneurons immature at the time of culturing. Supported by AetosTechnologies Inc.51 Poster Peripheral Olfaction and Peripheral TasteRESPONSES OF THE RAT OLFACTORY EPITHELIUM TOREVERSED AIR FLOWScott J.W. 1 , Humberto A.P. 1 , Sherrill L. 1 1 Cell Biology, EmoryUniversity, Atlanta, GAWe tested electroolfactogram (EOG) during inspiration (odorized airdrawn through the external nares by a vacuum applied to the trachea) orexpiration (odorized air pushed through the nose from the trachea) in 5rats. Two micropipettes were placed in the dorsomedial and lateralrecesses of the nasal cavity. Responses were tested to methyl benzoate,phenyl acetate, anisole, isoamyl acetate, limonene, vinyl cyclohexane,and heptane (listed in order of calculated water solubility) with astimulus duration of two seconds. Concentrations were selected toroughly match the sizes of the response at the better of the two sites foreach odorant. The same concentrations were used in all animals and theelectrodes remained in place throughout the experiment. Dorsomedialresponses were greatest to the soluble odorants, while lateral responseswere greatest to the insoluble odorants. These odorants were then testedduring expiration at the same concentrations using a longer stimulus (5seconds) to provide maximal opportunity for diffusion into the olfactoryarea. Responses to the insoluble odorants were roughly the size ofresponses during inspiration. Responses in the dorsomedial region werevery small during the stimulus, but for odorants in the midrange ofsolubility (e.g., anisole and isoamyl acetate) there was usually (in 4 ofthe 5 rats) a strong response when the flow was turned off, suggesting abackflow into the dorsomedial recess after expiration ceased. Retestwith inspiratory stimuli showed the original responses. These datasupport the concept that the physical chemical properties of odorants areimportant in determining response. They suggest that these propertiesmay be important in retronasal olfaction. Supported by NIH grantDCD00113.50 Poster Peripheral Olfaction and Peripheral TasteSTRUCTURE AND FUNCTION OF A TRACE DETECTORSYSTEM: CANINE OLFACTORY SYSTEMMorrison E. 1 , Josephson E. 1 , Viswaprakash N. 1 , Dennis J.C. 1 , Wang K. 2 ,Denny T. 2 , Vodyanoy V. 3 1 Anatomy, Physiology and Pharmacology,Auburn University, Auburn, AL; 2 Electrical Engineering, AuburnUniversity, Auburn, AL; 3 Auburn University, Auburn, ALStudies of the canine olfactory system are important for dogs, knownto be one of the best odorant trace detection systems, are utilized byhumans in tracking, rescue, explosive and drug detection missions.Canine detection offers the most powerful and cost effective programsavailable to law enforcement agencies. In the present study we utilizedimmunocytochemistry, electro physiology and computer modeling toexamine the canine olfactory system. Our results show that the mainand accessory olfactory system was positive for several specific neuralmarkers, NCAM, BT and OMP. Olfactory receptor neurons werelabeled for GAP-43 suggesting neurogenic activity is persistent in theadult canine olfactory system. In addition G protein subunits Gi and Gowere expressed in the sensory epithelium. Electrophysiological resultsshow that endogenous Gi protein negatively regulates odorant evokedintracellular signaling. This suggests a mechanism for controlling theactivities of adenyl-cyclases which could contribute to the ability ofolfactory neurons to discriminate odors. The complex canine nasalcavity was CT serially examined and combined with EOG data toproduce a one dimensional linear response model. Our results showedthat a sniff frequency of 7 Hz yields an optimal response. Thiscorresponded well with the normal 8Hz level recorded from workingdetector dog sniff rates. Currently, three dimensional reconstruction ofhuman and canine olfactory nasal cavity regions and steady airflowdynamics are underway. Supported in part by FAA G01-6-02, DARPAMDA 972-00-1-0 and Aethos Tech Inc52 Poster Peripheral Olfaction and Peripheral TasteOLFACTORY AND OTHER CHEMOSENSORY RECEPTORCELLS IN THE NASAL CAVITY OF THE AMERICANALLIGATORHansen A. 1 1 Rocky Mountain Taste and Smell Center, University ofColorado Health Sciences Center at Fitzsimons, Aurora, COCrocodilians including alligators possess the chemosensory systemsof olfaction and taste but unlike other reptiles, do not have avomeronasal organ. Alligators lead a semi-aquatic life and detect bothwater- and airborne chemical cues (Weldon et al., 1990, Ethology85:191-198). Little is known about the morphology of the olfactorysystem in this group of reptiles. The present study examined theepithelium of the nasal cavity of the American alligator (Alligatormississipiensis). Light and electron microscopic techniques wereutilized to establish the types of olfactory receptor neurons (ORNs) andtheir distribution in the nasal cavity. Furthermore, the possible presenceof solitary chemosensory cells (SCCs), a chemosensory cell found invarious epithelia of fish and in the respiratory epithelium of rodents,was investigated. The results indicate a scenario different from that inother vertebrates. Almost the entire nasal cavity is lined with olfactorysensory epithelium. However, the ORNs are more widely spaced than inother groups of vertebrates and the density of ORNs varies from rostralto caudal. Additionally, scattered cells occur in the olfactory epithelium,which are morphologically similar to SCCs as described for fishes androdents. The reason for the different distribution of ORNs and SCCsneeds further investigation. This study was supported by NIH grantsRO1 DC-06070 to T. E. Finger and P30 DC-04657 to Diego Restrepo.13