Association for Chemoreception Sciences (AChemS) 41ST Annual Meeting:
Smell and Taste: Our Link to the Environment
Press Abstracts

How To Bug A Spider:
Chemesthesis and TRP Channels in the Wolf Spider, Tigrosa georgicola.
Cecil J. Saunders, Hayden M. Graser, Nandan J. Patel, Glen S. Marrs, Erik C. Johnson
Wake Forest University, Department of Biology, Winston-Salem, NC, United States

Spiders primarily prey on other arthropods—including each other—and many arthropods produce chemical defenses to avoid predation. Many of these chemical defenses guard against vertebrate predation by modulating Transient Receptor Potential (TRP) channels. Thus, it seems probable that these chemical defenses may act to deter predation via activation of spider TRP channels as well. However, little is known regarding the identity or function of spider TRP channel homologs. In the present study, we present both behavioral assays and molecular data establishing the TRP-relevant chemesthestic repertoire of the wolf spider Tigrosa georgicola. Spiders reject prey crickets coated with allyl isothiocyanate (AITC) and menthol but consumed crickets treated with capsaicin normally. Additionally, we applied canonical chemesthetic compounds (AITC, methanol, capsaicin) to individual spider limbs. Stereotypical grooming behavior was immediately apparent after exposure to AITC and persisted for some time, in contrast to vehicle applications that showed no responsiveness. To determine the identity of TRP channel homologs, we extracted and sequenced RNA from the brains of T. georgicola (n=3). A de nova assembly of this neural transcriptome was then preformed with Trinity and annotated with Trinotate. Transcripts predicted to code for protein homologs of TRPA1, TRPC4, TRPC5, TRPM1, TRPM2 and TRPV4 were identified in the T. georgicola transcriptome and confirmed via RT-PCR.

How Parasitic Worms Hunt Down and Infect Hosts:
Deciphering the responses of skin-penetrating nematodes to carbon dioxide.
Navonil Banerjee, Spencer Gang, Elissa Hallem
University of California Los Angeles, Los Angeles, CA, United States

Skin-penetrating nematodes are gastrointestinal parasites that infect nearly one billion people worldwide. They respond robustly to a wide range of sensory cues. However, the specific roles of host-associated chemosensory cues in driving parasite-host interactions are poorly understood and the mechanisms underlying detection of such cues have not been investigated. We are studying the role of carbon dioxide (CO2) in promoting host-parasite interactions using the human-skin-penetrating threadworm Strongyloides stercoralis. Specifically, we are elucidating the role of CO2 in mediating three crucial steps of the parasite-host interaction: (a) host seeking, (b) development inside the host after skin penetration (activation), and (c) migration within hosts to complete the parasitic life cycle and establish an infection (intra-host navigation). We show that behavioral responses to CO2 differ across life stages. While infective larvae (iL3s) are repelled by CO2, activated iL3s are attracted and free-living adults are neutral to CO2. CO2 is also critical for triggering activation. CO2 repulsion by iL3s may function as a dispersal cue, driving them off host feces and into the soil to host seek. Once inside the host, CO2 attraction may direct activated iL3s to the host small intestine. We are now using CRISPR/Cas9-mediated targeted mutagenesis to identify genes required for CO2response in parasitic nematodes. We have found that the receptor guanylate cyclase GCY-9 mediates CO2-evoked responses in S. stercoralis, and that the S. stercoralis BAG neurons detect CO2. We are now investigating the neural mechanisms that enable S. stercoralis to generate life-stage-specific responses to CO2. Our results will provide insight into the chemosensory mechanisms that drive host-parasite interactions.

Restoring The Sense Of Smell:
Restoring the Sense of Smell: The Development of an Olfactory Implant System
Daniel H Coelho^1,2 & Richard M Costanzo^1,2
1Department of Otolaryngology Head & Neck Surgery, Virginia Commonwealth University, Richmond, VA, United States ²Department of Physiology and Biophysics, Virginia Commonwealth Univerisity, Richmond, VA, United States

Despite its prevalence and impact on quality of life, no viable treatments exist for the treatment of anosmia. To address this, our lab has been exploring the use of direct electrical stimulation of the olfactory bulb as a novel method to bypass damaged olfactory nerves to restore olfactory function. The ability to directly stimulate areas of the brain to activate losses of sensory percept is not without precedent. Cochlear, auditory brainstem, and retinal implants are only some of the increasingly common treatment options for those with loss of a special sense. The Olfactory Implant System (OIS) prototype consists of gas sensors, a microprocessor and an electrode array for direct stimulation of the olfactory system. Preliminary data using a rat olfactory nerve injury model shows that stimulation at different positions along the ventral surface of the bulb generates different patterns of evoked potentials activity recorded at the dorsal surface. By programming varying simulation patterns within the electrode array (similar to that used with cochlear implants), it should be possible to selectively activate different regions of the olfactory bulb, generating unique patterns of neural activity that lead to smell perception. Although in the early stages of development, the Olfactory Implant System (OIS) may ultimately do for acquired anosmia what the cochlear implant has done for sensorineural hearing loss.

Smell Tests May Predict Anxiety And Depression After A Concussion:
Evaluation and evolution of the olfactory dysfunctions within 24 hours after a mild traumatic brain injury (mild TBI)
Fanny Lecuyer Giguere^1,2,3, Andreas Frasnelli⁴, Elaine de Guise ^1,2,5, Johannes Frasnelli^1,3,6
1Department of Psychology, University of Montreal, Montreal, QC, Canada ²Centre de recherche interdisciplinaire en réadaptation du Montréal métropolitain (CRIR), Montreal, QC, Canada ³Hôpital du Sacré-Cœur de Montréal, Montreal, QC, Canada ⁴Emergency Department, Spitalzentrum Oberwallis, Visp, Switzerland ⁵Research Institute-McGill University Health Centre, Montreal, QC, Canada ⁶Department of Anatomy, Université du Québec à Trois-Rivières (UQTR), Trois-Rivieres, QC, Canada

Objective: This study aimed to evaluate olfaction 24 hours (baseline) and one year (follow-up) after a mild traumatic brain injury (TBI). We further evaluated the influence of the cognition and affective state on olfactory function. Method: At baseline, olfactory function, neuropsychological and affective state were assessed in 42 patients (20 mild TBI; 22 orthopedic injury). At follow-up, 12 patients with mild TBI and 7 controls could be included and we assessed olfactory function, affective states and post-concussion symptoms. Results: At baseline, patients with mild TBI demonstrated significantly reduced olfactory function, compared to controls, with more than 55% of the patients presenting sings of hyposmia. At follow up, no significant differences in olfactory scores between cases and controls were observed. However, patients with mild TBI who had exhibited hyposmia at baseline exhibited significantly higher anxiety levels and more post-concussion symptoms than patients with mild TBI with normal olfactory function at baseline. Conclusions: In the acute phase of mild TBI a majority of patients has impaired olfactory function. Further patients with olfactory dysfunction are more likely to exhibit post-concussion and anxious symptoms at follow-up. Olfactory testing in the acute phase may therefore serve as a screening tool for long term outcome.

A Novel Salty Taste Receptor In Mice:
TMC6: A Novel Salt Taste Receptor in Mice Takami Maekawa¹, Koki Kamiya², Tooru Takahashi^1,3, Kentaro Kaji^1,3, Yukio Tezuka ^1,3, Toshihisa Osaki², Shoji Takeuchi^2,4, Takashi Kondoh^1
1Ajinomoto Co., Inc., Kawasaki, Japan ²Kanagawa Institute of Industrial Science and Technology, Kawasaki, Japan ³WDB Co., Ltd., Tokyo, Japan ⁴Institute of Industrial Science, The University of Tokyo, Tokyo, Japan

Mechanism of amiloride-insensitive salt taste perception remains unclear. To find novel salt taste receptors, we investigated gene and protein expression in taste cells. Among them, it was found that transmembrane channel-like 6 (TMC6), a protein with unknown functions, was expressed in taste cells by single cell PCR and immunohistochemistry analysis. To perform functional analysis of TMC6, we generated Tmc6 knockout mice with C57BL/6J background and found that NaCl preference of the Tmc6 (-/-) mice, in the presence of amiloride, was largely decreased compared to the wild-type mice. Interestingly, the Tmc6 (-/-) mice showed normal preferences to sweet, sour, bitter and umami solutions. The results suggested that Tmc6 gene relates specifically to salt taste perception. By calcium imaging of CHO-K1 cells transfected withTmc6 gene, we found that the cells responded to NaCl stimulus. Finally, we embedded a purified TMC6 protein in an artificial lipid bilayer membrane and observed single ion channel-like currents under NaCl application. These results suggest that TMC6 is a novel ion channel that functions as a novel salt taste receptor in mouse taste cells.

Children’s Preference And Ability To Detect Sugars Differ From Adults:
Sweet Taste Detection and Preference in Children vs. Adults
Sara Petty¹, Clara Salame¹, Julie A. Mennella², M. Yanina Pepino^{1 1}University of Illinois Urbana-Champaign, Champaign, IL, United States ²Monell Chemical Senses Center, Philadelphia, PA, United States

Adults and children might live in different sensory worlds. In particular, children prefer sweeter substances than adults do. This may be related to their increased energy need in periods of maximal growth and development. However, there is limited published data that uses the same methods to compare the taste worlds of children and adults, particularly with respect to taste sensitivity. Here we compared data collected from children aged 7-18yrs. (n=182) to data collected from several studies in adults aged 21-67yrs. (n=117) using identical, validated, methods. We assessed sucrose detection thresholds by using a two-alternative, forced-choice paired comparison tracking procedure, and sucrose preference with the Monell 2-series, forced-choice tracking method. We found that sucrose detection thresholds were higher in children than adults (log means of -2.04±0.03 vs. -2.18±0.04 in children vs. adult respectively; ~9.2mM vs. 6.7mM sucrose; p<.01). As expected, children preferred higher sucrose concentrations than adults (595 ±22 mM vs. 433 ±27 mM; p<.0001). Sucrose detection threshold were not correlated to sucrose preference in either group (children, r=0.013; adults, r=0.166 both P’s>0.05). Our results indicate that children are less sensitive to detect sucrose than adults are, and confirms previous findings that children prefer higher concentrations of sucrose. However, sucrose detection thresholds did not predict preference, and therefore children's preference for heightened sucrose concentrations cannot be explained by a reduced sucrose sensitivity at detection levels. Further understanding of children’s taste perception world can help to contribute to the understanding of the motivations behind food choices made by children and their potential nutritional implications.

Undetected Olfactory Loss Has No Major Impact On Your Functioning:
Presence of undetected olfactory loss in the general population - based on a large sample of 9139 subjects
Anna Oleszkiewicz^1,2, Ilona Croy¹, Valentin Schriever¹, Antje Haehner¹, Thomas Hummel^1
1TU Dresden, Dresden, Germany ²University of Wroclaw, Wroclaw, Poland Presented data were analyzed to provide up-to-date and more detailed normative data based on a large-scale sample to increase validity of the diagnosis by creating the possibility to refer individuals to more narrow age-groups. Previous normative values lacked higher sample sizes especially in the group of older subjects. Data was obtained from 9139 subjects, of whom 4928 were females aged 5 – 96 years (M=31.8, SD=18.9) and 4211 were males aged 5 - 91 years (M=30.7, SD=17.7). All subjects were healthy. They were tested with a standard “Sniffin’ Sticks” test comprising Threshold, Discrimination and Identification subtests. With this extended sample, we found hyposmia to be defined as less than 30.75 points of the TDI score. We confirmed age-related changes in each domain, but it was most pronounced for threshold. Individuals aged 20-30 years showed the highest values, while children below the age of 10 and adults above the age of 71 performed only half as well. Sex-related differences were in favor for women. Importantly, in this sample of relatively young and healthy people we found a meaningful proportion of subjects scoring in the range of hyposmia or functional anosmia, who seem not to be aware of the olfactory dysfunction or seem not to be bothered by it. Their demographical characteristic will be presented together with detailed olfactory scores.

Roses Make Life Sweeter, But Only In The Lab :
Interaction of taste and smell on perception of sweetness in honey bees
Allyson V. Pel, Stephanie R. Hathaway, Susan E. Fahrbach
Department of Biology, Wake Forest University, Winston-Salem, NC, United States

Perception of sweetness depends on sugar content of foods, but organic volatiles produced by certain fruits result in an overestimation of sweetness by humans. It is unknown if this phenomenon occurs in other species. This project focuses on how the interaction of smell and taste modulate perception of sweetness in honey bees (Apis mellifera). Honey bees are generalist foragers that forage for nectar of varying sweetness at different flowering plants; it is well-documented that they readily discriminate different concentrations of sucrose and show a strong preference for higher concentrations. Honey bees also experience floral odors as they forage, creating the possibility that the combination of taste and odor might modulate perception of sweetness. Linalool, geraniol, and 6-methyl-5-hepten-2-ol were used as odorants that may enhance the perception of sweetness by honey bees found in some of the flowering plants honey bees forage upon; limonene and no odorant were used as controls. Bees were tested using proboscis extension response (PER) laboratory assays and gustatory acceptance score (GAS) field assays. In the PER assays, only geraniol enhanced sweetness perception in honey bees compared with the limonene and no odor treatments. By contrast, there was no difference in responses to any compounds in the field studies. In the laboratory, the effect of these odorants on sweetness perception was age-dependent. To our knowledge, this is the first demonstration of the modulation of the perception of sweetness in an insect by simultaneous olfactory input.