1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

21 Slide Ecology and Social ChemicalsCHEMICALS AND ECOLOGY: MULTITROPHIC PREDATORPREY INTERACTIONS MEDIATED BY CHEMISTRYFerrer R.P. 1 , Zimmer R. 1 1 Ecology and Evolutionary Biology,University of California, Los Angeles, CADuring development, sensory systems undergo changes in cellreceptor machinery. Such modifications may alter the way an animalperceives its olfactory environment. Here we investigate a cannibalisticinteraction between two discrete life history stages of the Californianewt (Taricha torosa). The defense compound tetrodotoxin (TTX), inadult newt skin is recognized by conspecific larvae as an avoidancesignal. Yet, antipredator behavior is suppressed when TTX is mixedwith odors from alternative adult prey. In laboratory assays, newt larvaewere exposed to TTX alone, or in binary mixtures with test compoundsisolated from invertebrate prey tissues. The larval escape response toTTX (0.1 µM) was significantly reduced when Arg (0.1 to 0.01 µM)was added. Free-ranging adult newts were exposed to components ofprey tissue extracts in the field. Arg was the most attractive compoundtested, evoking plume-tracking behavior at concentrations as low as 10nM. A comparable array of Arg analogs and TTX/Arg analog mixtureswas tested on adults and larvae, respectively. Adult responses wereeliminated by even slight alterations to Arg, such as the addition of asingle carbon to the side chain or esterification of the α-carboxyl group.In contrast, larval responses to TTX were inhibited by Arg as well as byanalogs with the guanidinium group. Thus, adults were more narrowlytuned than larvae to Arg analogs. These results show that Arg hasopposing effects (inhibitory/stimulatory) on larval/adult newts, andapparently acts on different suites of olfactory receptors for individualsof the two, distinct, life history stages.22 Slide Ecology and Social ChemicalsENANTIOMERIC PHEROMONE BLENDS IN MAMMALS:ASIAN ELEPHANTS AND BARK BEETLES SHARE CHIRALCHEMISTRYGreenwood D. 1 , Rasmussen L. 2 1 School of Biological Sciences,University of Auckland, Auckland, New Zealand; 2 Environmental &Biomolecular Systems (EBS), Oregon Health & Science University,Portland, ORFrontalin (1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane) a bicyclicketal of terpene origin can exist in two chiral or mirror image forms.Our recent finding that both enantiomeric forms of frontalin are presentin the temporal gland secretions of male Asian elephants during musth(Greenwood et al., Nature 438:1097-8, 2005) mirrors that seen in anumber of bark beetle species. Moreover changes in the ratio of the twoforms has implications for chemical signalling in both diverse phyleticgroups as important behavioral consequences are dependent on this. Ourresults suggest that stereochemical control of the enantiomeric ratioimplemented during biosynthesis involving a putative dihydroxylationstep provides modulation of the pheromonal message. This modulationis likely translated into a differential message at the level of pheromonereception based on the inherent chiral selectivity of receptor proteins.Supported by ISAT.23 Slide Ecology and Social ChemicalsBEHAVIORAL EVIDENCE THAT GOLDFISH DISCERNMOSAICS OF PHEROMONAL ODORANTS THAT INCLUDEBOTH SEX HORMONE DERIVATIVES AND BILE ACIDSSorensen P.W. 1 , Fine F. 2 , Murphy C. 2 , Bjerselius R. 2 , Kihslinger R. 31 University of Minnesota, St. Paul, MN; 2 Fisheries, Wildlife, andConservation Biology, University of Minnesota, St. Paul, MN;3 Neurobiology, Physiology and Behavior, University of California,Davis, Davis, CAAlthough behavioral studies have established that many species ofteleost fish employ species-specific pheromonal odors to mediatereproduction, all cues identified to date are common hormonal productsincapable of imparting species-specific information. A possibleexplanation for this phenomenon is that fish discern mixtures or`mosaics´ of odorants which include compounds such as bile acids(taxon-specific steroids released via the fish gut). Here, we tested thispossibility for the goldfish. Examining bile acid release, we found thatwhile most fish release similar suites of bile acids, their ratios differ.Thus, goldfish release mostly cyprinol sulfate (a bile acid specific tominnows), trout release mostly taurocholic acid, and gouramis releasemostly cholic acid (see Thwaits et al., this conference). Examining theolfactory sensitivity and specificity of the goldfish olfactory system toseveral dozen bile acids using EOG recording, we next found thatcyprinol sulfate is especially potent with a detection threshold of 10-11M. Cross-adaptation studies found sensitivity to be highly specific.Finally, we found that behavioral responses of male goldfish to 15 ketoprostaglandinF2a (a pheromonal cue released by female goldfish) wasstrongly suppressed by the addition of bile acids only released by otherspecies. In conclusion, odor mixtures seem important to naturalpheromone function in fish. (NSF 9723798).24 Slide Ecology and Social ChemicalsPHEROMONAL RECOGNITION MEMORY INDUCED BYTRPC2-INDEPENDENT VOMERONASAL SENSINGKelliher K.R. 1 , Spehr M. 1 , Li X. 1 , Zufall F. 1 , Leinders-Zufall T. 11 Anatomy and Neurobiology, University of Maryland at Baltimore,Baltimore, MDOne of the best known examples of olfactory imprinting in adultvertebrates is the selective pregnancy block (or Bruce effect) in themouse, which depends on the formation and maintenance of apheromonal recognition memory by the vomeronasal system. Peptideligands of major histocompatibility complex (MHC) molecules are thefirst identified vomeronasal stimuli that can mediate the Bruce effect,but the molecular mechanisms underlying this effect remain to beexplored. The cation channel gene TRPC2 plays a critical role in thesignal transduction mechanism of vomeronasal sensory neurons (VSNs)and TRPC2 -/- mice constitute an important genetic model forinvestigating the role of the vomeronasal organ (VNO) in mammalianpheromonal sensing. By using mice with a homozygous deficiency inTRPC2, we tested whether TRPC2 is essential for a pheromonalrecognition memory. Surprisingly, the loss of the TRPC2 channel genedoes not significantly influence the establishment of this memory,whereas, surgical lesions of the VNO do. Furthermore, field potentialand single cell patch-clamp recordings show that TRPC2 is dispensablefor the transduction of MHC peptide ligands by sensory neurons in thebasal zone of the VNO. This indicates that a previously unrecognizedTRPC2-independent signal transduction mechanism in the VNOunderlies the formation of this pheromonal recognition memory.Supported by grants from NIH/NIDCD (to K.R.K, F.Z., and T.L.-Z.)and the Emmy Noether Program of the DeutscheForschungsgemeinschaft (to M.S.).6