2009 Abstracts - Association for Chemoreception Sciences

animals over the age of P24 were given solutions using a drinkingtube. Animals were sacrificed 2 days after their last treatment toobserve immediate effects of the treatment. Contrary to whatmight be expected given previous research, adult rats’ taste budswere more susceptible to capsaicin than neonates. Specifically,adults treated with CAP had significantly smaller taste buds 2days post treatment than adults treated with SUC. Such an effectwas not observed in neonates. Tongues were also analyzed 50 dayspost treatment to identify any possible regeneration of volumes,and surface analyses were performed at both 2 and 50 day timepoints to determine papillae count and morphology.#P295 Poster session VI: Chemosensory developmentand Psychophysics ICompetitive Effects of GSP and IX Nerve Transection onthe Maturation of CT Terminal Field Volume in theNucleus of the Solitary TractSara L Dudgeon, David L HillUniversity of Virginia Charlottesville, VA, USANeural competition among multiple inputs can affect theorganization of circuits in many sensory systems; however, thishas not been examined in the developing gustatory system. Thedegree of overlap among the greater superficial petrosal (GSP)nerve, the glossopharyngeal (IX) nerve, and the chorda tympani(CT) nerve terminal fields in the rostral nucleus of the solitarytract (NTS) is greatest early in development and decreases asanimals age to adulthood. To assess the effects of lack ofcompetition from the GSP and IX on the development of the CTterminal field, we sectioned the GSP and the IX at postnatal day15 (P15), P25 or P65. At 35 days post nerve section, the CT waslabeled and its terminal field was subsequently imaged andanalyzed. The results show that sectioning GSP and IX at P15results in a CT terminal field volume at adulthood that is similarto P15 controls and much greater than that of adult, uncutanimals. Therefore, the CT terminal field does not reorganize andprune back as it does in normal development when competitiveinfluences from GSP and IX are removed. Animals in which GSPand IX were cut at P25 or P65 also have CT terminal fieldvolumes comparable to P15 controls. This indicates that the CTnerve remains plastic into adulthood and is still subject to theeffects of competition. Preliminary evidence shows no changes inperipheral function of the CT nerve prior to GSP and IXregeneration, and significant loss (or absence) of palatal andposterior tongue taste buds at 30 days post nerve section. Thesestudies provide evidence that competition between individualinputs to the gustatory system plays a role in organizing theterminal fields.#P296 Poster session VI: Chemosensory developmentand Psychophysics IPostnatal development of trigeminal neuronal sensitivity tocapsaicin, nicotine, and innocuous coolingJiang Xu 1 , Valery Audige 2 , Nancy Rawson 3 , Bruce Bryant 11Monell Chemical Senses Center Philadelphia, PA, USA,2University of Pennsylvania Philadelphia, PA, USA, 3 Wellgen, Inc.North Brunswick, NJ, USAChanges in behavioral repertoire that occur over the course ofmaturation may reflect changes in peripheral neuronalpopulations. We examined trigeminal neuronal sensitivity inneonatal (2-3 day) and adult (5 week) rats to capsaicin (CAP,200nM), nicotine (NIC,100uM) and cooling (31.5 to 18C) usingintracellular calcium responses as an index of neuronalsensitivity. The overall proportions of neurons sensitive to each ofthe stimuli remained the same over 5 weeks of development.However, the proportion of different subtypes of neonatal andadult neurons sensitive to 1, 2 or 3 of the stimuli changed.Percentages were calculated on the basis of total number ofneonate or adult neurons tested (n=304 and 580) and sorted intosubtypes responsive to none,1,2, or 3 stimuli. In nicotine-sensitiveneurons, the proportion of CAP-sensitive cells was similar inneonates and adults. However, the proportion of cells sensitive toboth cooling and nicotine was higher in neonates than adults. Thisdifference between neonates and adults was most pronounced inthe proportion of cool-sensitive neurons also responsive tocapsaicin (8.5% vs 4.4%, respectively). Consistent with neonatalbehavioral aversion to cooling, these neurons are likelynociceptors that are also sensitive to innocuous cooling. Thecapsaicin dose-response function differed insignificantly ( t-test,p=0.12) in terms of EC50 in the two age groups (adult, 72.5±4nM,n=137; neonate, 55.6±10.9nM, n=112), while the S-nicotineconcentration (0.1-1000uM) response function was nearlyidentical in neonatal and adult trigeminal neurons. Our datasuggest that changes in neuronal subtypes may account forchanges in behavioral phenotype and for some purposes, neonataltrigeminal neurons may not be a good model for neuronalresponse patterns of the adult.#P297 Poster session VI: Chemosensory developmentand Psychophysics IDevelopment of the olfactory organ in fish: a comparisonAnne Hansen 1 , Peter Bartsch 2 , Eckart Zeiske 31University of Colorado Denver, CO, USA, 2 HumboldtUniversity Berlin, Germany, 3 University of Hamburg Hamburg,GermanyLocation and shape of the olfactory organ as well as structure anddevelopment of the olfactory epithelium (OE) vary greatly in rayfinnedfish (Actinopterygii). There is still considerable lack ofinformation regarding the development of the olfactory organ inmany basal taxa. This information is crucial for reconstruction ofthe evolution of this sensory system and the phylogeny ofosteognathostomes (the monophyletic group of osteichthyanfishes and tetrapods). In this study we examined the developmentof the olfactory organ in “primitive” groups that are close to thedichotomy of ray-finned fishes and lobe-finned fishes andtetrapods. We employed LM, TEM and SEM methods andcompared the development of the olfactory organ in Polypterus(bichir) to that of Acipenser (sturgeon) and teleosts. Our resultsindicate the following plesiomorphic (primitive) character statesin bichirs: The primary olfactory pit is formed by invagination ofP O S T E R SAbstracts | 119