Catfish electroreceptor organ functioning during five days exposure to different calcium environments |
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| Authors: | RC Peters RHS Westerink |
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| Institution: | (1) Comparative Physiology, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands (Fax;(2) Research Institute of Toxicology (RITOX), Utrecht University, Yalelaan 2, 3508 TD Utrecht, The Netherlands (Fax: + 31.30.2535077, E-mail: R.Westerink@ritox.vet.uu.nl) |
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| Abstract: | Catfish, Ictalurus melas, were pre-adapted to artificial tap water with 1.2 mM Ca2+ for two weeks, and subsequently transferred to artificial tap water with 0.6, 1.2, or 2.2 mM Ca2+ for one week in order to investigate the effect of the environmental Ca2+-concentration on stimulus encoding and the frequency characteristics in ampullary electroreceptor organs. Within 30 minutes after transfer, the spontaneous activity of the primary afferents, as well as gain and phase of the stimulus induced responses changed transiently corresponding to the Ca2+-concentration. One day after transfer the Ca2+-induced changes of the spontaneous activity had disappeared as well as the differences between the sensitivities at frequencies of 2, 8, 12, 16 and 20 Hz in 0.6 and 1.2 mM Ca2+, whereas at 16 and 20 Hz in 2.2 mM Ca2+ the sensitivity was still elevated. The Ca2+-induced phase shift was strongly frequency dependent. At 2 Hz no Ca2+ effect on the phase was observed, whereas at 12, 16 and 20 Hz significant effects could be demonstrated up till three days after transfer. The latency was not affected by the transfer.The Ca2+-induced effects on the primary afferent spontaneous activity are probably related to a Na+/Ca2+-exchanger at the basal faces of the receptor cells. The frequency dependent effects on gain and phase are concluded to relate to properties of the apical membrane, most likely to Ca-dependent K-channels. These findings further support the concept that ampullary electroreceptor might serve as chemoreceptor organs. |
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| Keywords: | chemoreception electroreception hair cells homeostasis Ictalurus Saffan stanniocalcin stimulus transduction synaptic efficacy |
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