2009 Abstracts - Association for Chemoreception Sciences

elationship in the characteristic response (pheromone searchingbehavior) of male moths to pheromone called bombykol releasedby conspecific females. However, little is known about the precisetemporal characteristics of peripheral input in relation to theinitiation of pheromone searching behavior because the difficultyin controlling and administering olfactory stimuli still remain tobe solved. To address the problem, we generated a transgenicsilkmoth expressing channelrhodopsin-2 (ChR2), a blue lightgatedion channel identified in green algae, under the control of aputative promoter sequence of BmOR1, the bombykol receptorgene in silkmoth. ChR2 expressing male displayed typicalpheromone searching behavior in response to a single pulsed bluelight stimulation. Probability of behavioral response wasdependent on duration of stimulation, and response thresholdtime was 3 ms that evoked a single spike in bombykol receptorneurons in single sensillum recordings. When input informationwas decreased by covering a half region of antennae, probabilityof behavioral response was significantly reduced, which recoveredto a normal level by a second stimulation given within a timewindow of approximately 120-240 ms. These results suggest thatthe triggering of behavior is simply determined by the collectiveamount of spiking information summated within few hundredmilliseconds.#P97 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyOlfactory Thresholds of ElasmobranchsTricia L Meredith, Stephen M KajiuraFlorida Atlantic University Boca Raton, FL, USAOlfactory capabilities of elasmobranchs are legendary. Althoughreputed to demonstrate remarkable odor sensitivities, thisperception is based on surprisingly little empiricalevidence. Olfaction plays an important role in the localization ofprey, and amino acids in particular are effective odorants forelasmobranchs. However, olfactory sensitivity has been assessedfor only four elasmobranch species using a handful of aminoacids. Literature values for these species indicate thresholds to beapproximately 10 -7 to 10 -8 M. The aim of this study was to surveythe olfactory thresholds of five phylogenetically diverseelasmobranch species (Dasyatis sabina, Urobatis jamaicensis,Raja eglanteria, Negaprion brevirostris, and Sphyrna tiburo) inorder to develop a representative picture of their olfactorycapabilities. The electro-olfactogram (EOG) technique was usedto assay the sensitivities of these species to a suite of twentyproteinogenic amino acids. Both the relative stimulatoryeffectiveness of the tested amino acids and their estimatedthresholds (~10 -7 to 10 -9 M) across all five tested elasmobranchspecies were similar. These results indicate that elasmobranchspecies do not demonstrate greater olfactory sensitivity thanteleost fishes.#P98 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyCycloheximide: an effective taste aversion UCSBradley K Formaker, Kumudini Chintalapati, Thomas PHettinger, Marion E FrankUniversity of Connecticut Health Center Farmington, CT, USAA single oral exposure to 0.5 mM cycloheximide (Cyx) results inan increased aversive behavioral potency towards Cyx (Hettingeret al., 2007). To test if this increased potency is the result of denovo taste receptor induction or the ability of Cyx to act as anunconditioned stimulus in aversion learning, we behaviorallytested 4 groups (n=6) of golden hamsters (Mesocricetus auratus)and electrophysiologically recorded from 2 groups. All behavioralanimals were maintained on a restricted water drinking schedulethroughout the experiment. One group drank 100 mM sucrosebefore injection with 0.5 mM Cyx (mixed in 154 mM NaCl; 12.4ml/kg bw; ip). This dose approximates the amount of 0.5 mM Cyxnaïve hamsters ingest in 1 hr. A control group drank 100 mMsucrose before injection with 154 mM NaCl. A second controldrank distilled water before injection with Cyx and the last groupdrank 0.5 mM Cyx before injection with NaCl. Hamsters exposedto sucrose and injected with Cyx showed robust behavioralavoidance to sucrose (~80% suppression) compared to all othergroups, which did not differ from each other. The sucroseaversion remained robust through 4 weeks of testing. Chordatympani (CT) responses were recorded in 2 groups (n=3) ofhamsters culled from the 4 behavioral groups. One group wasorally exposed to 0.5 mM Cyx and the other group was notexposed to Cyx at all. Cyx failed to activate the CT atconcentrations up to 1 mM, regardless of Cyx exposure.These results suggest that the increased aversive behavior towardsCyx, following initial exposure, is due to the effectiveness ofCyx as an unconditioned stimulus in aversion learning.#P99 Poster session II: Chemosensory response to,and control of, feeding/NeuroethologyEnantioselective Odorant Receptor in the Yellow FeverMosquito, Aedes aegyptiJonathan D. Bohbot, Joseph C. DickensUSDA, ARS, BARC, PSI, IIBBL Beltsville, MD, USAEnantiomers, non-superimposable mirror image molecules, havebeen shown to drive important behaviors of a wide range oforganisms from insects to humans. Enantiomer recognition ispredicated on the organism’s capability to discriminate thesechiral olfactory signals. The existence of enantiomer-specificreceptors in other molecular recognition processes and theextensive body of physiological evidence for such mechanisms inolfaction have long argued for the existence of enantiomer-specificodor receptors. Using the two-microelectrode voltage clamptechnique with Xenopus oocytes expressing the mosquito Aedesaegypti OR8 (AaOR8), we were able to show for the first timedirect evidence that an insect receptor discriminates the twoenantiomers of 1-octen-3-ol. Not only is AaOR8 enantioselective,but proper chain length and degree of unsaturation are alsoimportant chemical features necessary for its full activation. Thisenantioselective odorant receptor provides a molecular basis forthe chiral specificity exhibited by insect olfactory sensoryneurons. This work was supported in part by a grant to J.C.D.P O S T E R SAbstracts | 57