Summary
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1.
Threshold currents as function of temperature were determined on the isolated Lorenzinian ampullae of the dogfish. Currents were applied via microelectrodes in the orifice of the ampullary canal. Response frequencies of single afferent units were averaged for at least 100 successive identical stimulus pulses by means of autocorrelation functions and periodograms. The threshold was defined by a 10% change of response frequency caused by the stimulus.
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2.
The lowest threshold current for the single ampulla was found to be about 0.01 nA at temperatures between 13 °C and 19 °C. This current corresponded to a current density of ca. 8 nA/cm2, or to a potential difference of 2 μV between the ampullary canal and the grounded exterior.
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3.
There was a strong temperature dependence of electrosensitivity of the ampulla: the threshold currents increased with lower (7 °C) and higher temperatures (25 °C) by a factor of about 10.
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4.
The threshold currents found by computer averaging were smaller by a factor of at least 10 than those given up to now for the single isolated ampulla, and corresponded well to the values estimated in behavioural experiments on the living animal. This fact might be explained by spatial summation in the electrosensory system.
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A preliminary report was given by Bromm, Hensel, and Tagmat 1975
Supported by the Deutsche Forschungsgemeinschaft
The experiments were performed at the Biologische Anstalt Helgoland. We wish to thank Prof. Dr. O. Kinne for his hospitality and support, Mr. J.-K. Holtmann for his help during the adaptation procedure, and Mrs. v. Rehren and Miss Walter for technical assistance.
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Bromm, B., Hensel, H. & Tagmat, A.T. The electrosensitivity of the isolated ampulla of lorenzini in the dogfish. J. Comp. Physiol. 111, 127–136 (1976). https://doi.org/10.1007/BF00605528
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DOI: https://doi.org/10.1007/BF00605528