1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

397 Poster Central Taste and Chemosensory BehaviorINJECTION OF CHOLECYSTOKININ INTO THE WAISTAREA OF THE PARABRACHIAL NUCLEUS INCREASESTASTE REACTIVITY RESPONSES TO INTRA-ORALINFUSION OF QUININE IN RATSKing M.S. 1 , Delmond J. 1 , Maddox L.C. 2 1 Biology, Stetson University,DeLand, FL; 2 Daytona Beach Community College, Daytona Beach, FLNeurons in the waist area of the parabrachial nucleus (W) processtaste input and project to medullary regions that generate taste reactivityresponses. Cholecystokinin (CCK) is a gut-brain peptide that has beenimplicated in satiation. Since CCK and its receptors are located in W,we hypothesized that this peptide influences the processing of tasteinformation thereby altering the oromotor responses to taste input. Totest this hypothesis, 10 mM CCK (400 nl) was injected into the ponsthrough implanted guide cannula (Plastics One) in 12 male Wistar ratsimmediately before intra-oral infusion of 0.01 M NaCl, 0.01 M sucroseand 0.003 M quinine HCl. The injection of CCK into W increased thenumber of gapes and tongue protrusions performed following intra-oralinfusion of quinine as compared to when vehicle was injected on thefollowing day (n = 5, p < 0.05). Although there was a trend for feweringestive behaviors following intra-oral infusion of NaCl when CCKwas present, this effect was not statistically significant (p = 0.098).Taste reactivity responses to sucrose were not altered by CCKinjections. Indicating that these effects of CCK were due to actionwithin or near W, injections just dorsal, medial and rostral to W did notalter oromotor responses to the intra-oral infusion of any tastant used.These preliminary results suggest that CCK may act within the waistarea of the parabrachial nucleus to alter oromotor behaviors to tasteinput. [Supported by NSF RUI 0090641 and NIH R01 DC07854-01].398 Poster Central Taste and Chemosensory BehaviorALTERED PARABRACHIAL TASTE PROCESSING IN OBESEOLETF RATSLundy R. 1 , Hajnal A. 2 1 Anatomical Sciences & Neurobiology,University of Louisville, Louisville, KY; 2 Neural & Behavioral Sciences,Pennsylvania State University, Hershey, PAOtsuka-Long-Evans-Tokushima-Fatty rats (OLETF) lack functionalCCK-1 receptors, are hyperphagic, and gradually develop obesity anddiabetes during their life span. Recently we have reported a greaterpreference for sucrose in prediabetic OLETF compared to age-matched,lean controls (LETO). This study investigated sucrose taste processingin the pontine parabrachial nucleus using a semi-chronic preparationthat allowed data collection over several recording sessions (e.g. 12, 13,15, 16, 19, and 20 wks of age). Forty-four taste neurons were tested and,using cluster analysis, categorized based on response profile to 0.1 MNaCl, 0.01 M citric acid, 0.003 M QHCl, and six sucrose concentrations(0.01, 0.03, 0.1, 0.3, 1.0, and 1.5 M). These neurons were furtherdivided into Block 1 (wks 12&13) and Block 2 (wks 15–20)representing different stages of glucose tolerance. For NaCl-best cells,the Block 2 response rates to 0.1, 0.3, 1.0, and 1.5 M sucrose were 21%to 47% smaller relative to Block 1 sessions in OLETF, but not LETOrats. Sucrose-best cells (S-best), on the other hand, were 15% to 69%more responsive to these concentrations of sucrose during Block 2sessions relative to Block 1 sessions both for OLETF and LETO rats.The net effect was to alter the across-neuron pattern evoked by sucrose.That is, advancing age in OLETF rats, but not LETO rats, increased thepercentage of sucrose information carried by S-best cells. This effectmay contribute to the increased behavioral sensitivity to palatable mealsin this strain. Supported by NIH grants DK065709 and DC006698.399 Poster Central Taste and Chemosensory BehaviorTHE PROPERTIES OF INHIBITORY TASTE NEURONS INTHE PARABRACHIAL NUCLEUS OF RATSLei Q. 1 , Yan J. 1 , Yang X. 1 , Shi J. 1 , Chen K. 1 1 Physiology &Pathophysiology, Xi'an Jiaotong University Medical Center, Xi'an,Shaanxi, ChinaIn rodents, the parabrachial nucleus (PBN) is the second relay of thetaste system, that receives projection from the gustatory portion in thenucleus solitary. Our earlier study found that there was some tasteneurons with inhibitory response to taste stimuli in addition to themajority of taste neurons with excitatory response in PBN. The aim ofthe present study was to characterize the spontaneous and evokedactivities of the inhibitory gustatory neurons of PBN . The single PBNneurons were recorded extracellularly and identified by the responses ofthe neurons to taste stimuli including 0.3 M NaCL, 0.01 M HCL, 0.003M QHCL and 0.5 M Sucrose in the anesthetized rat. A total of 19inhibitory neurons were studied. The spontaneous firing rates of theseneurons were in the range of 0.5-30 Hz and were depressed remarkablyand quickly, from 3.89 ± 1.85 Hz to 0.46 ± 0.09Hz, by application oftaste stimuli. The inhibition lasted about 5-80s. Most of them respondedto more than one of the tastants. On the basis of their largest inhibitoryresponses to the four basic stimuli. these inhibitory taste neurons wereclassified as follows: NaCL-best (56.3%); HCL-best (12.5%); QHCLbest(12.5%) Sucrose-best (18.7%).These findings suggest that there areinhibitory taste neurons in PBN that may play role in modulation ofgustatory information. Supported by the National Natural ScienceFoundation of China(No. 30270454 and 30300111)Correspondingauthor: Janqun Yan.400 Poster Central Taste and Chemosensory BehaviorEFFERENT PROJECTION FROM THE BED NUCLEUS OFTHE STRIA TERMINALIS SUPPRESSES ACTIVITY OFTASTE-RESPONSIVE NEURONS IN THE HAMSTERPARABRACHIAL NUCLEILi C. 1 , Cho Y.K. 2 1 Anatomy, Southern Illinois University, Carbondale,IL; 2 Physiology & Neuroscience, Kangnung National UniversityCollege of Dentistry, Kangnung, Kangwon-do, South KoreaAlthough the reciprocal projections between the bed nucleus of thestria terminalis (BNST) and the gustatory parabrachial nuclei (PbN)have been demonstrated neuroanatomically, there is no direct evidenceshowing that the projections from the PbN to the BNST carry tasteinformation or that descending inputs from the BNST to the PbNmodulate the activity of PbN gustatory neurons. In the present study, werecorded from 105 taste-responsive neurons in the PbN and examinedtheir responsiveness to electrical stimulation of the BNST bilaterally.Twelve neurons (11.4%) were antidromically invaded from the BNST,mostly from the ipsilateral side (11 cells), indicating that a subset oftaste neurons in the PbN project their axons to the BNST. The BNSTstimulation induced orthodromic responses on most of the PbN neurons:103 out of 105 (98.0%), including all projection units that weremodulated by BNST stimulation. This descending modulation on thePbN gustatory neurons was exclusively inhibitory. We also confirmedthat activation of this efferent inhibitory projection from the BNSTreduces taste responses of PbN neurons in all units tested. The BNST isknown to be involved in sodium appetite and taste aversion learning.The BNST is also participates in the neural circuits that involve stressassociatedfeeding behavior. Therefore, this neural substrate may beimportant in taste aversion learning and sodium appetite as well as thestress-elicited alteration in ingestive behavior. Supported byNIDCD006623100