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- Olfactory transduction pathways in the Senegalese sole Solea senegalensisPublication . Velez, Zélia; Hubbard, Peter; Barata, E. N.; Canario, Adelino V. M.This study tested whether differences in sensitivity between the upper and lower olfactory epithelia of Solea senegalensis are associated with different odorant receptors and transduction pathways, using the electro-olfactogram. Receptor mechanisms were assessed by cross-adaptation with amino acids (L-cysteine, L-phenylalanine and 1-methyl-L-tryptophan) and bile acids (taurocholic acid and cholic acid). This suggested that relatively specific receptors exist for 1-methyl-L-tryptophan and Lphenylalanine (food-related odorants) in the lower epithelium, and for taurocholic acid (conspecificderived odorant) in the upper. Inhibition by U73122 [a phospholipase C (PLC) inhibitor] suggested that olfactory responses to amino acids were mediated mostly, but not entirely, by PLC-mediated transduction (IC50; 15–55 nM), whereas bile acid responses were mediated by both PLC and adenylate cyclase–cyclic adenosine monophosphate (AC–cAMP) (using SQ-22536; an AC inhibitor). Simultaneous application of both drugs rarely inhibited responses completely, suggesting possible involvement of non-PLC and non-AC mediated mechanisms. For aromatic amino acids and bile acids, there were differences in the contribution of each transduction pathway (PLC, AC and non-PLC and non-AC) between the two epithelia. These results suggest that differences in sensitivity of the two epithelia are associated with differences in odorant receptors and transduction mechanisms.
- Evidence for functional asymmetry in the olfactory system of the senegalese sole ( solea senegalensis )Publication . Velez, Zélia; Hubbard, Peter; Barata, E. N.; Canario, Adelino V. M.The two olfactory epithelia of flatfish of the family Soleidae are essentially in contact with two distinct environments; the upper (right) side samples open water while the lower (left) side samples interstitial water. This study assessed whether there are differences in the responsiveness of the two epithelia by use of the electro‐olfactogram in the Senegalese sole (Solea senegalensis). The upper epithelium was significantly more responsive to the basic amino acids (l‐lysine and l‐arginine), glycine, and l‐threonine than the lower epithelium. The lower epithelium was significantly more responsive to aromatic amino acids (l‐tryptophan, l‐tyrosine, l‐DOPA, and l‐phenylalanine), l‐leucine, and l‐asparagine than the upper. Both epithelia had similar responsiveness to the sulphur‐containing amino acids (l‐cysteine and l‐methionine), l‐alanine, l‐serine, and l‐glutamine. Neither side was responsive to the acidic amino acids (l‐aspartate and l‐glutamate) or the D‐isomers of any amino acid tested. The upper olfactory organ was much more responsive to conspecific‐derived stimuli (bile and intestinal fluid) than the lower organ. We suggest that these differences in responsiveness may be related to different functional roles of the upper and lower epithelia in feeding and chemical communication.
- Anatomy of the olfactory system and potential role for chemical communication in the sound‐producing lusitanian toadfish, halobatrachus didactylusPublication . Modesto, Teresa; Gregório, Beatriz Neves; Marcelino, Gonçalo; Marquet, Nathalie; Costa, Rita; Guerreiro da Costa Guerreiro, Pedro Miguel; Velez, Zélia; Hubbard, PeterThe current study investigated the structure and function of the olfactory system of the Lusitanian toadfish, Halobatrachus didactylus, using histology and electrophysiology (electro-olfactogram [EOG]), respectively. The olfactory system consists of a digitated anterior peduncle, of unknown function, containing the inhalant nostril. This then leads to a U-shaped olfactory chamber with the olfactory epithelium-identified by G(alpha olf)-immunoreactivity-on the ventral surface. A large lacrimal sac is connected to this tube and is likely involved in generating water movement through the olfactory chamber (this species is largely sedentary). The exhalent nostril lies by the eye and is preceded by a bicuspid valve to ensure one-way flow of water. As do other teleosts, H. didactylus had olfactory sensitivity to amino acids and bile acids. Large-amplitude EOG responses were evoked by fluid from the anterior and posterior testicular accessory glands, and bile and intestinal fluids. Anterior gland and intestinal fluids from reproductive males were significantly more potent than those from non-reproductive males. Male urine and skin mucus proved to be the least potent body fluids tested. These results suggest that chemical communication-as well as acoustic communication-may be important in the reproduction of this species and that this may be mediated by the accessory glands and intestinal fluid.