The effect of Cu(II) on the electro-olfactogram (EOG) of the Atlantic salmon ( Salmo salar L) in artificial freshwater of varying inorganic carbon concentrations

Abstract

The effect of inorganic copper species was studied by recording the receptor potential, electro-olfactogram (EOG), from the olfactory epithelium of Atlantic salmon ( Salmo salar L). In a series of experiments, the olfactory organ was irrigated with aqueous copper solutions with concentrations of the free cupric ion (Cu 2+) ranging from 0.2 to 9.7 μ M. The diverse copper species were created by varying the amount of bicarbonate (NaHCO 3) in artificial freshwater solutions of equal total copper concentrations. In general, these copper solutions induced a slow depolarization of the baseline followed by a hyperpolarization. The amplitudes of these variations in baseline potentials increased with increasing concentrations of Cu 2+ ion, i.e., decreasing concentrations of NaHCO 3. Stimulating the olfactory epithelium with l-alanine during the copper exposure evoked atypical EOG responses. The amplitudes and form of the EOGs changed drastically with increasing Cu 2+ concentrations, with significant correlation between the reduction in EOG amplitudes and the Cu 2+ concentration. The results indicate that among the copper species tested the toxic effect is caused mainly by the dissolved Cu 2+ ion. The results also suggest that the Cu 2+ ion exerts its toxic effects on the transduction mechanisms of the olfactory receptor cells. The different EOG profiles obtained in response to varying Cu 2+ concentrations indicate that this ion affects the transduction mechanisms at different stages.