1 1 Symposium Chemosensory Receptors Satellite DEVELOPMENT ...

293 Poster Central Olfaction and Chemical EcologyRECONSTITUTION OF A CHEMICAL DEFENSE SIGNALINGPATHWAY IN A HETEROLOGOUS SYSTEMPadove S.A. 1 , Kubanek J. 2 , Hatt H. 3 , McCarty N.A. 1 1 School of Biology,Georgia Institute of Technology, Atlanta, GA; 2 School of Biology,School of Chemistry & Biochemistry, Georgia Institute of Technology,Atlanta, GA; 3 Cell Physiology, Ruhr-University Bochum, Bochum,GermanyBecause marine sponges are sessile and cannot physically escapepredators, many contain chemical defense compounds that deterpredation by reef fishes; however, it is unknown how these fishphysiologically detect these chemicals. The objective of this study wasto determine if a signaling pathway for chemical defense compoundscould be reconstituted in a heterologous expression system. Zebrafish(Danio rerio) rejected foods laced with some sponge chemical defensecompounds, including sceptrin, previously shown to deter a generalistmarine predator (Thalassoma bifasciatum). Therefore, clones from awhole zebrafish cDNA library were expressed in Xenopus oocytes. Thelibrary-expressing oocytes were tested by electrophysiological methods,using the CFTR chloride channel and the endogenous calcium-activatedchannel as reporters for chemoreceptor activation. Control experimentsshowed that CFTR activity can be a good indicator of OR-I7 receptoractivation in oocytes injected with cRNA for that receptor. Octanal andisoproterenol both activated currents in oocytes co-expressing thezebrafish library and CFTR. Furthermore, oocytes expressing libraryand CFTR, but not uninjected oocytes, showed an electrophysiologicalresponse to sceptrin. Therefore, we conclude that zebrafish can detectmarine sponge-derived chemical defense compounds, and oocytes canreconstitute the sceptrin-activated signaling pathway. Funding: NSF-IGERT fellowship.294 Poster Central Olfaction and Chemical EcologyGENETIC MODEL OF HIGH RESPONSIVENESS TOPREDATOR ODORVoznessenskaya V. 1 , Krivomazov G. 1 , Voznesenskaia A. 1 ,Klyuchnikova M. 1 1 Institute of Ecology & Evolution RAS, Moscow,RussiaRisk of predation may significantly affect the behavior of potentialprey. Chemosensory detection may be an important aspect of predatoravoidance strategy for many mammals. New genetic model has beendeveloped using rats of heterogeneous laboratory population. Thephenotype of interest is high responsiveness to predator odor. In ourearlier studies we examined the influence of predator chemical cuesderived from feral cat urine on reproductive output of rodents: rats,mice and voles. Animals responded to predator chemical cues withreduced litter size and skewed sex ratio. The reduction in litter size inrodents exposed to predator urine was attributable to suppressedprogesterone levels affecting the implantation of embryos. During eightyears (1997-2005) we selected rats of heterogeneous laboratorypopulation for high embryo resorption rate (over 20%, H-line) andaccordingly for low resorption rate (less then 10%, L-line) underpredator odor exposures. Currently we have 14-th generation of rats ofH-line. Rats of H-line have significantly (p < 0.001) higher percent offemales with 100% resorption rate of embryos under predator odorexposures relative to rats of L-line and rats of heterogeneouspopulation. Also there are significant (p < 0.001) differences in littersize between animals of H and L line under predator odor exposures.Developed genetic model may be a useful tool for chemical analysis ofpredator chemical signals. Supported by RFBR 04-04-48723 and byRussian Academy of Sciences, Program “Biological Resources” #3.1.7.295 Poster Central Olfaction and Chemical EcologyTHE ROLE OF THE VOMERONASAL ORGAN IN ALARMPHEROMONE PERCEPTIONKiyokawa Y. 1 , Kikusui T. 2 , Takeuchi Y. 2 , Mori Y. 2 1 Japan Society forthe Promotion of Science, Tokyo, Japan; 2 Laboratory of VeterinaryEthology, University of Tokyo, Tokyo, JapanWe previously reported that alarm pheromone in male Wistar ratswas released from their perianal region and aggravated stress-inducedhyperthermia, known as the indices of animal's anxiety status, inpheromone recipient rats. In addition, we found that this pheromonecould be trapped in water. Although alarm pheromone had increasedFos expression in the accessory olfactory bulb of recipients, we stillhave no clear evidence whether this pheromone is perceived by themain olfactory system or by the vomeronasal system. In the presentstudy, we assessed this issue by exposing alarm pheromone to the threetypes of the recipients, i.e., intact male, vomeronasal organ excised(VNX) male and VNX-sham male. As was done in our previous studies,alarm pheromone-containing water was prepared by the electricalstimulation to the perianal reigon of an anesthetized donor rat in a smallbox containing water droplets on the ceiling. The odor released fromneck region of the donor was used as control odor. After the watercollection, the filter papers containing one type of the water samplewere placed on the wall of the recipient's home cage, and autonomicresponses were monitored for the subsequent 30 min. Alarm pheromonesignificantly aggravated stress-induced hyperthermia in intact andVNX-sham (p < 0.05, ANOVA) recipient as compared to those seen incontrol odor and vehicle control groups. However, the VNX recipientdid not show this autonomic response to alarm pheromone. Theseresults strongly suggest that alarm pheromone in male rats is perceivedby the vomeronasal organ. This study was supported by the JapanSociety for the Promotion of Science (JPSP) and by ResearchFellowships of the JSPS for the Promotion of Science for YoungScientists.296 Slide Peripheral OlfactionCONTEXT-DEPENDENT MODULATION OF OLFACTORYEPITHELIAL ACTIVITY BY THE TERMINAL NERVE INAXOLOTLS (AMBYSTOMA MEXICANUM)Polese G. 1 , Eisthen H.L. 1 1 Zoology, Michigan State University, EastLansing, MIActivity in the vertebrate olfactory epithelium appears to bemodulated by peptides released from the terminal nerve, which containsGnRH as well as another peptide that displays NPY-likeimmunoreactivity. In previous studies we have shown that GnRHmodulates odorant responsiveness in the olfactory epithelium and Na +and K + currents in olfactory receptor neurons. To determine whetherNPY also exerts modulatory effects, we obtained synthetic axolotl NPYfor use in physiological experiments. NPY is involved in manyactivities in the central nervous system, but most attention has focusedon its role in regulating appetite and hunger. We therefore examined theeffects of NPY on the olfactory epithelium in axolotls that were fedeither 1 or 10 days prior to testing ("well-fed" and "hungry",respectively). Using electro-olfactogram recordings, we found that bathapplication of 1 µM NPY increased the magnitude of odorant responseselicited by L-glutamic acid (100 µl at 10 mM) in hungry animals but notin well-fed animals. Using whole-cell recordings from olfactoryreceptor neurons in epithelial slices, we found that bath application of0.1 - –1 µM NPY resulted in an increase in the magnitude of the TTXsensitiveNa + current in more than 50% of olfactory receptor cells inhungry axolotls, but none in well-fed animals. Taken together with ourprevious results indicating that the effects of GnRH vary across thebreeding season, these data suggest that modulation of activity in theolfactory epithelium by the terminal nerve depends on the animal´sphysiological context. Supported by NIH (RO1 DC05366).74