2009 Abstracts - Association for Chemoreception Sciences

#P103 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyPerception of Threshold and Suprathreshold Taste Stimuli inObese and Normal-Weight WomenM. Yanina Pepino 1,2 , Susana Finkbeiner 1 , Gary K. Beauchamp 1 ,Julie A. Mennella 11Monell Chemical Senses Center Philadelphia, PA, USA,2Washington Univerisity in St. Louis, School of Medicine St. Louis,MO, USAThe goal of the present study was to determine whether obesewomen exhibit altered umami and sweet taste perception whencompared to normal weight women. To this end, each of 56subjects participated in a two-day study separated by one week.Half of the women were evaluated using mono sodium glutamate(MSG; prototypical umami stimulus) on the first test day andsucrose on the second test day; the order was reversed for theremaining women. We used two-alternative forced-choicestaircase procedures to measure taste detection thresholds, aforced-choice tracking technique to measure preferences, thegeneral Label Magnitude Scale to measure perceived intensity ofsuprathreshold concentrations and a triangle test to measurediscrimination between 29mM MSG from 29mM NaCL. We findthat although obese women required a higher concentration ofMSG to detect a taste, their perception of MSG at suprathresholdconcentrations, their ability to discriminate MSG from salt, andtheir preference for MSG and sweets were similar to that observedfor normal-weight women. Regardless of their body weightcategory, 28% of the women did not discriminate 29 mM MSGfrom 29 mM of NaCl (Non Discriminators). Surprisingly, wefound that Non Discriminators at suprathreshold MSGconcentrations had similar MSG detection thresholds thanDiscriminators. Taken together, these data suggest that differentmechanism may be involved in the perception of threshold andsuprathreshold MSG concentrations.#P111 Poster session II: Cortical chemosensoryprocessing/Receptor genomics and molecular biologyGroup III metabotropic glutamate receptors modulatetransmission of taste information in primary taste afferentsRobert M HallockUniversity of Colorado School of Medicine Aurora, CO, USAPrimary afferent taste fibers use glutamate as the majortransmitter at their central terminals in the nucleus of the solitarytract (nTS). We investigated the role of metabotropic glutamatereceptors (mGluR) in regulating transmission in the primarygustatory nucleus of goldfish, the vagal lobe (homologous to thevagal gustatory portion of the nTS in mammals). We used an invitro slice preparation of the vagal lobe to determine the effects ofmGluR agonists/antagonists in transmission of gustatoryinformation. In this preparation, primary gustatory afferents wereelectrically stimulated, while evoked dendritic field potentials(fEPSP) were recorded in the sensory layers of the vagal lobewhere the afferents terminate. We have previously shown that anmGluR agonist (L-AP4) attenuates synaptic components of thefEPSP to electrical stimulation of the primary taste afferent fibers.Here, we extended these findings by examining responses to anmGluR antagonist, MAP4. In Experiment I, we confirmed thatL-AP4 significantly depressed the fEPSP. Then, the addition ofMAP4 reversed the inhibitory effects of L-AP4 (p