2009 Abstracts - Association for Chemoreception Sciences

and 2) the number of CT neurons with regenerated peripheralaxons. Transgangionically transported fluorescent label allows usto compare the volume of vestigial and functional CT nerveterminal field post-CTX. Our results indicate that CT cells do notdie following CTX, despite attenuated regeneration of peripheralaxons. In addition, measures of labeled CT terminal fields in therNTS indicate 1) a lack of degeneration, and 2) a reduction incentral axons that are functionally connected to peripheraltargets. Such measures will be useful for understanding injuryinducedchanges seen in experimental animal populations andtaste abnormalities seen in human patients after CT nerve injury.#P43 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsA Network Model of Taste Processing in the Nucleus of theSolitary TractA.M. Rosen 1 , H. Sichtig 2 , J.D. Schaffer 2,3 , P.M. Di Lorenzo 11Dept. of Psychology, Binghamton University Binghamton, NY,USA, 2 Dept. of Bioengineering, Binghamton UniversityBinghamton, NY, USA, 3 Philips Research, North Am.Briarcliff Manor, NY, USAThough the functional architecture of many primary sensorynuclei has been well characterized, the organization of the nucleusof the solitary tract (NTS), the first central relay for gustation,remains a mystery. Here, we used electrophysiological datarecorded from single cells in the NTS to inform a network modelof taste processing. Previous studies have revealed that stimulationof the chorda tympani (CT) nerve initiates two forms ofinhibitory influences in separate groups of NTS cells. These formsof inhibition differed in time course and were correlated withdistinct NTS taste response properties. That is, one inhibitoryinfluence peaked early, decayed rapidly and was associated withshort latency responses to CT stimulation and narrow tuningacross tastants. Conversely, the second inhibitory influencepeaked late, decayed slowly and was seen in cells with longlatency responses to CT stimulation and broad tuning. Based onthese data, we designed a model of the NTS consisting of discretecell assemblies with a projection neuron and two different typesof inhibitory interneuron. Each cell assembly is reciprocallyconnected to every other and is characterized by a distinct profileof sensitivity across tastants. Input to the network of integrateand-firemodel neurons was based on recordings from the CTnerve. Responses to taste stimulation as well as paired-pulse CTstimulation were simulated. The network dynamics of the NTSmodel operated in a “winner-take-all” fashion, where differencesin the stimulus sensitivities between assemblies enhanceddiscrimination between taste qualities. We propose that suchdynamics may account for the coherence in across neuronpatterns of NTS responses between similar tastants.#P44 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsLinoleic acid does not enhance chorda tympani nerveresponses to sucrose, citric acid and quinine hydrochlorideJennifer M Stratford, Robert J ContrerasFlorida State University Department of Psychology and Programin Neuroscience Tallahassee, FL, USAPrevious studies suggest that the chorda tympani nerve (CT) isimportant in carrying fat taste information to the central nervoussystem, as bilateral transection of the CT (CTX) raises the tastediscrimination threshold for the free fatty acid, linoleic acid (LA).Surprisingly, the CT is unresponsive to lingual application of LAalone. However, electrophysiological studies of isolated tastereceptors have shown that LA inhibits delayed rectifyingpotassium channels, presumably broadening action potentials,and augmenting responses to other taste stimuli (Gilbertson et al,1997). Thus, the contribution of the CT in this process maydepend upon the presence of other taste stimuli. In this regard,we previously found that co- application of LA and eithermonosodium glutamate (MSG) or sodium chloride (NaCl)elicited greater CT responses than did either MSG or NaClpresented alone (Stratford et al, 2008). In the present study, werecorded CT electrophysiological activity in response to tastemixtures of LA and sucrose (SUC), citric acid (CA), or quininehydrochloride (QHCl) in anesthetized male rats. Unlike theeffects observed with MSG and NaCl, we found that the additionof LA did not alter CT responses to SUC, CA and QHCl.However, CT is weakly responsive to SUC, CA and QHCl inrats. Therefore, CT whole nerve recordings may lack thesensitivity to detect small changes in CT responses to these tastestimuli. It is more probable, however, that LA may affect CTresponses to MSG and NaCl only, perhaps by specificallymodulating gustatory processing of Na+- which is found in bothMSG and NaCl. This possibility may be explored in futurestudies using a pharmacological antagonist of epithelial sodiumchannels or a non sodium salt, such as potassium chloride.#P45 Poster session I: Chemosensory disorders,models and aging/Central chemosensory circuitsImprovement of olfactory function in patients treatedfor chronic rhinosinositis is related to increasing olfactorybulb volumeVolker Gudziol, Dorothee BuschhüterSmell and Taste Centre Dresden, GermanyAim of the present study was to investigate whether the humanolfactory bulb (OB) volume increases after short-term treatmentof olfactory function. Nineteen patients with chronicrhinosinositis with polyps were investigated. All patients receivedfunctional endoscopic sinus surgery. In addition, 18 volunteerswithout history and endoscopic signs of chronic rhinosinositiswere also investigated. Measurements were performed on 2occasions separated by 3 months in patients and 4 month incontrols. Olfactory function was evaluated in great detailseparately for each nostril; MR scans of the OB wereperformed. Volumetric measures of the OB were based onplanimetric manual contouring. In healthy controls the OBvolume was not significantly different between the twomeasurements. In contrast, OB volume in patients increasedsignificantly from initial 64.5 ± 13.9mm³ to 70.0 ± 15.3mm³40 | AChemS Abstracts 2009