title: Olfactory sensitivity to amino acids in the blackspot sea bream (Pagellus bogaraveo): a comparison between olfactory receptor recording techniques in seawater.
abstract: The current study investigated the olfactory sensitivity of the blackspot sea bream to amino acids, odorants associated with food detection in fish, and compared the efficacy of two different experimental methods: multi-unit recording from the olfactory nerve and the electro-olfactogram (EOG). Twenty essential amino acids plus L-DOPA evoked clear, concentration-dependent olfactory responses using both methods, with estimated thresholds of 10(-8.5)-10(-6.2) M (nerve recording) and 10(-7.5)-10(-4.8) M (EOG). The most potent amino acids were L-cysteine, L-methionine (both sulphur-containing), L-alanine, L-leucine (both neutral), L-glutamine (amide-containing) and L-serine (hydroxyl-containing). The least potent were L-proline (secondary α-amino group), the aromatic amino acids and glycine (simplest). Although the rank order of olfactory potency was similar for the two methods used, and the calculated thresholds given by the two methods were positively correlated, the sensitivity of the EOG was consistently lower than multi-unit recording by approximately one order of magnitude, presumably due to the electrical shunting effect of seawater. As in freshwater, the EOG could be a valid method for comparing olfactory potency of different odorants in stenohaline marine fish; however, for absolute 'biological' thresholds, a more invasive recording technique, such as multi-unit recording from the olfactory nerve, should be used.
authors.affiliation: Centro de Ciências do Mar, Universidade do Algarve, Campus de Gambelas, 8005-139, Faro, Portugal. phubbard@ualg.pt
authors.forename: Peter C
authors.initials: PC
authors.lastname: Hubbard
authors.forename: Eduardo N
authors.initials: EN
authors.lastname: Barata
authors.forename: Rodrigo O A
authors.initials: RO
authors.lastname: Ozório
authors.forename: Luisa M P
authors.initials: LM
authors.lastname: Valente
authors.forename: Adelino V M
authors.initials: AV
authors.lastname: Canário
mesh_terms: D000596:Amino Acids / Q000145:classification / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D055724:Electrophysiological Phenomena / Q000187:drug effects; D016014:Linear Models; D009812:Odorants; D009832:Olfactory Nerve / Q000187:drug effects / Q000502:physiology; D018034:Olfactory Receptor Neurons / Q000187:drug effects* / Q000378:metabolism; D021541:Sea Bream / Q000502:physiology*; D012623:Seawater; D012680:Sensitivity and Specificity; D012684:Sensory Thresholds / Q000187:drug effects; D012903:Smell / Q000502:physiology*
chemical_list: D000596:Amino Acids