title: Evidence that olfactory sensitivities to calcium and sodium are mediated by different mechanisms in the goldfish Carassius auratus.
abstract: The current study investigated whether the olfactory sensitivity to Ca2+ and Na+ is mediated by the same mechanism in the goldfish, a freshwater teleost. The olfactory responses, as assessed by recording the electro-encephalogram (EEG) from the olfactory bulb, to changes in external [Ca2+] and to [Na+] were recorded in the absence and presence of increasing concentrations of the other ion. Low concentrations of Na+ (0-1.0mM) had no significant effects on the olfactory response to changes in [Ca2+] in terms of EC50, Imax or Hill co-efficient (n=8). A relatively high concentration of Na+ (10mM) significantly reduced the Imax and increased the EC50. One hundred millimolars Na+ reduced the olfactory response to Ca2+ to undetectable levels. Conversely, low concentrations of Ca2+ (0.1 and 1.0mM) significantly attenuated the olfactory response to changes in environmental [Na+], reducing the amplitude of response and increasing the threshold of detection (n=7). However, a high concentration of Ca2+ (10mM) failed to attenuate the olfactory response to Na+ completely. Taken together, these results suggest that, at normal environmental concentrations of these ions, Ca2+ and Na+ are detected by distinct and separate cellular mechanisms. However, there seems to be a degree of overlap between the two mechanisms. The exact mechanisms involved, and their biological roles, remain to be established.
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: Adelino V M
authors.initials: AV
authors.lastname: Canário
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004569:Electroencephalography / Q000187:drug effects; D006054:Goldfish / Q000502:physiology*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology; D009830:Olfactory Bulb / Q000187:drug effects / Q000378:metabolism*; D009831:Olfactory Mucosa / Q000187:drug effects / Q000378:metabolism*; D009832:Olfactory Nerve / Q000187:drug effects / Q000378:metabolism*; D012684:Sensory Thresholds / Q000187:drug effects / Q000502:physiology; D012903:Smell / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D012964:Sodium; D002118:Calcium