2009 Abstracts - Association for Chemoreception Sciences

These findings demonstrate the capacity of EX-4, a GLP-1agonist to reduce preference for palatable sucrose solutions, andsuggest diminished sensitivity to the postoral component of thiseffect in DIO rats maintained on high fat diet. These observationstogether with data showing an attenuated GLP-1 release after ameal and an increased preference for sweet in obese individualssuggest a causal link between diminished intestinal GLP-1feedback and orosensory sensitivity to sweet, and may also helpwith promoting a novel application for GLP-1 agonists to combatsweet cravings and overeating.#P83 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyState-dependent Yeast Intake in Drosophila melanogasterOsama Ahmed, Beth Gordesky-Gold, Paul A. S. BreslinMonell Chemical Senses Center Philadelphia, PA, USASpecific hungers may arise as a result of metabolic stress. Forinstance, it has been shown that protein-malnourished humanbabies prefer soups that are high in protein over plain or sucrosefortifiedsoups. We aim to utilize the fruit fly as a genetic model ofthe human nutritional need and appetite for protein. Mostinfamously, female mosquitoes require a blood meal prior to egglaying. In the current study, we sought to determine if nutrientintake of Drosophila melanogaster is affected in a similar way.Mated, virgin, and male wild type Drosophila melanogaster weregiven a choice between equivalent concentrations of yeast andsucrose solutions. Mated flies showed greater consumption ofyeast than virgin females or male flies, while sucrose ingestionremained similar among all three groups. The increase in yeastintake indicates an initial preference for yeast over sucrose.However, yeast preference was not stable throughout theexperiment but rose and fell, behavior consistent with egg laying.These results suggest a state-dependent protein appetite in matedDrosophila, which may result from alterations in nutritional needsas the organism prepares for oviposition.#P84 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyA Behavioral Assay using Drosophila to Test forChemesthetic Irritants Activating TRPA1 ChannelsWayne L. Silver, Matthew W. Greene, Paige M. Roe, Erik C.JohnsonWake Forest University Winston-Salem, NC, USAChemesthesis is the sense of irritation produced by chemicals. Inmammals, the trigeminal nerve mediates chemesthesis in the headand face. Chemical irritants stimulate the trigeminal nervethrough a variety of receptor proteins, including TRPA1 which isactivated by over 90 compounds. Fruit flies, Drosophilamelanogaster, possess a painless gene which is the homolog ofmammalian TRPA1. We compared behavioral responses toirritants in wild-type and painless mutant flies in a feeding choiceassay (Al-Anzi et al, 2006) to determine whether irritants whichactivate trigeminal nerve responses in mammals also stimulate flyTRPA1. A 96-well plate served as the test arena with half the wellscontaining sucrose and blue dye and the other half containingsucrose plus irritant and red dye. In half of the tests, the color ofthe food choice was reversed to eliminate color preference.Fifty flies were starved for 24 hours, and then released into thetest arena. After one hour of feeding, the flies were examinedunder a microscope to determine what they ate. Flies were scoredfor blue, red or purple abdomens. The number of flies consumingeach food choice was quantified and a preference index was usedto determine which chemicals the flies avoided. Elevencompounds were tested at a concentration of 5mM. Eight of thesecompounds elicited significantly different responses in the wildtypeand painless mutant. These included allyl-isothiocyante,eugenol, nicotine, a-terpineol, amyl acetate, benzaldehyde, andd-limonene. Acetic acid, toluene, and cyclohexanone did notproduce significantly different responses. These results are similarto descriptions of the chemical sensitivity of mammalian TRPA1.Thus, this fruit fly assay might serve as a useful screen fortrigeminal nerve irritants which activate TRPA1.#P85 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyIntake of Fructose and Sucrose Solutions as aFunction of ConcentrationJennifer A. Cassell, James C. Smith, Thomas A. HouptProgram in Neuroscience, The Florida State UniversityTallahassee, FL, USAThere have been few direct comparisons of fructose (F) andsucrose (S) intake to determine differences in drinking patternsacross multiple isocaloric concentrations. Adult male SD rats(275-300g) were divided into S and F groups (n=8/group), andindividually housed in “hotel” cages which continuouslymonitored rats’ access to powdered chow (3.6 kcal/g) and numberof licks at each of 2 drinking bottles in 6-s bins. Drinking bottlesand chow were weighed and replenished daily. Each week, ratswere given access to water, a single concentration of sugar (S or F)and chow for 5 days, followed by a 2 day break with chow andwater only. Rats were tested with S (0-1.0M) or F (0-2M)solutions in ascending order. Water intake was negligible whensugar was available. Sugar intake was significantly greater thanbaseline water intake at or above 0.03M S or 0.06M F. Intake as afunction of concentration peaked at 0.25M S (136±15g/d) and0.5M F (138±12g/d). When expressed as caloric density, theconcentration-intake curves for S and F were not significantlydifferent, with a peak at 0.34kcal/g. While S and F intake wassimilar, there was a significant effect of sugar type on chow intakeand lick rate. Sucrose rats decreased chow intake as S increasedabove 0.03M (0.04kcal/g). Fructose rats did not significantlydecrease chow intake compared to baseline and ate significantlymore chow than S rats when drinking 0.08 kcal/g solutions andabove. Thus, cumulative caloric intake was much greater in F rats(3607±63 kcal) than S rats (2025±107 kcal, p