2009 Abstracts - Association for Chemoreception Sciences

#P112 Poster session III: Cortical chemosensoryprocessing/Receptor genomics and molecular biologySubnuclear organization of parabrachial taste neuronsprojecting to reward-related forebrain structures inC57BL/6J miceKenichi Tokita, John D. BoughterUniversity of Tennessee Health Science Center Memphis,TN, USASensations elicited by taste involve not only qualitative, but alsohedonic evaluation of stimuli. In fact, feeding and drinkingbehaviors of animals including humans are largely based on thisaffective evaluative outcome. Although the neural pathwaysunderlying these processes have not yet been well clarified, it isthought that taste information is conveyed to the reward systemof the brain, whose essential components are the ventral tegmentalarea (VTA) and nucleus accumbens. Neurons in the pontineparabrachial nucleus (PbN), the second taste relay in rodents,send axons to the ventral tegmental area as well as to the forebraingustatory areas such as the gustatory thalamus (VPMpc), centralnucleus of the amygdala, bed nucleus of the stria terminalis andinsular cortex. However, it is not clear whether 1) VTA-projectingneurons in the PbN also send axon collaterals to forebraingustatory areas, and 2) these neurons are taste-responsive. In thecurrent study, we performed functional neuroanatomicalexperiments combining c-Fos immunochemistry and retrogradetracing techniques to understand how the taste system interactswith the reward system in the mouse, an animal model withincreasing importance in various fields of neuroscience. Theretrograde tracers Fluorogold (FG) and cholera toxin subunit b(CTB) were iontophoretically injected into the VTA and VPMpcrespectively, and retrogradely-labeled neurons and sucroseevokedc-Fos expression in the PbN were visualized withimmunofluorescence. Some neurons were double labeled with FGand c-fos or triple labeled with FG, CTB, and c-fos. These resultssuggest that taste neurons in the PbN project both to the taste andreward systems. This work was supported by DC000353.#P113 Poster session II: Cortical chemosensoryprocessing/Receptor genomics and molecular biologyCloning and Localization of Four Putative SerotoninReceptors in the Primary Olfactory Pathway of theMoth Manduca sextaWujie Zhang 1 , Mike A. Miller 1 , Akshay Muralidhar 1 , Joel B.Dacks 2 , Andrew M. Dacks 1 , Alan J. Nighorn 11Arizona Research Laboratories, Division of Neurobiology,University of Arizona Tucson, AZ, USA, 2 Department of CellBiology, University of Alberta Edmonton, AB, CanadaSerotonin (5-hydroxytryptamine, or 5HT) functions as aneuromodulator in the antennal lobes (ALs; the primary olfactorycenter) of the moth Manduca sexta. To elucidate the molecularand cellular mechanisms behind the physiological effects of 5HTin the AL, and to further our understanding of its modulatoryrole, we are studying 5HT receptors in the primary olfactorypathway of Manduca. We previously reported the cloning of twoputative 5HT receptors from Manduca, Ms5HT1A andMs5HT1B. We cloned a third putative 5HT receptor, Ms5HT7,and partially cloned a fourth putative 5HT receptor, Ms5HT2.Using sequence analysis, we demonstrate that the full length andpartial clones exhibit high similarity to characterized 5HT7 and5HT2 receptors (respectively) from other insects. Using RT-PCR,we have determined that all four putative 5HT receptors areexpressed in both the AL and antenna of adult moth. We havegenerated antisera against Ms5HT1A and Ms5HT1B; Westernblots of AL tissue using the Ms5HT1A and Ms5HT1B antiseraproduced single bands at 51kDa and 48kDa, respectively. Inaddition, we have generated riboprobes for Ms5HT1A,Ms5HT1B, and Ms5HT7 for in situ hybridization. Using thesereagents, we are investigating the cellular expression patterns ofthe receptors in the AL through immunohistochemistry and insitu hybridization to identify specific AL cells or cell types wherethe receptors may mediate the effects of serotonin.#P114 Poster session III: Cortical chemosensoryprocessing/Receptor genomics and molecular biologyOR37 - receptors: a unique subfamily of olfactory receptorsHeinz Breer, Hoppe Rainer, Zhang Yongquan, Strotmann JörgUniversity Hohenheim, Institute of Physiology Stuttgart,GermanyOlfactory sensory neurons (OSNs) which express the sameodorant receptor (OR) gene are generally widely dispersedthroughout the olfactory epithelium. In contrast, OSNsexpressing a receptor of the OR37 family are assembled in asmall central patch. Besides the unique topographic expressionpattern, OR37 receptors display several other special features. Allmembers of the subfamily share a considerable sequence identity,moreover, they all have an insertion of six amino acids in the thirdextracellular loop. Based on this unique structural feature it isconceivable that the OR37 receptors may be tuned to a definedgroup of ligands. This notion is supported by comparative studiesindicating that orthologous receptors also exist in diversemammalian species, e.g. mouse, dog, primates. Even in humans,this group of receptors exists, with a surprisingly high fraction ofpotentially functional genes, a scenario that is against the generaltrend of pseudogenization for OR genes in humans. Whencomparing the coding sequence of OR37 genes an unexpectedhigh degree of sequence conservation across species borderemerged. The bioinformatic data strongly suggest that the OR37genes apparently are under a negative selective pressure, which isuntypical for OR genes but supports the idea that the OR37receptors are tuned to unique odorous ligands. Also the axonalprojection pattern of OR37 expressing neurons was found to beunique. All neuron populations of the various OR37 subtypesproject their axons onto a small, distinct area of the bulb, whereeach population formed a single glomerulus; all of them located inclose vicinity. During development, from E15 to P0, axons ofdifferent subpopulations terminate in a common area; in a shortpostnatal period (P3) the formation of distinct glomeruli isaccomplished.62 | AChemS Abstracts 2009