Fresh-water Fish Chemoreceptors Responsive to Dilute Solutions of Electrolytes

Abstract

The existence of the palatal chemoreceptors responding specifically to dilute solutions of salts with monovalent cations was demonstrated in carp. The distilled water effect (a response produced by the application of distilled water after chemoreceptors had been rinsed out with hypertonic salt solutions) was assigned to the activity of the same receptor. Intensity of the response to dilute solutions of salts depended on the valency of the anion: the larger the valency, the greater the response. Positively charged sites of the receptor responsive to dilute salt solutions were suggested by previous treatments with acid and alkali, and dye salts. Increase in the ionic strength of the stimulating solution by the addition of supporting electrolytes caused a depression of response. In particular, strong depression of response was caused by the addition of a supporting electrolyte with a divalent cation. Effects of polarizing current on the chemoreceptor activity were investigated. Based upon the findings in this paper, a hypothesis is presented, which explains mechanisms underlying chemoreceptor responses to dilute solutions of electrolytes in terms of an interfacial electrokinetic process.

On the Stimulation of Fish Chemoreceptors by Dilute Solutions of Polyelectrolytes

“…A high sensitivity of fish chemoreceptors to dilute electrolyte solutions has previously been reported (Komsm and NIWA, 1964: KONISHI, 1966, 1967KONISHI and HIDAKA, 1967). The recorded response vs. concentration curve displays a convex shape having a maximum at extremely low concentration.…”

“…The procedure for obtaining the palatine nerve preparation was the same as that previously described (KONISHI and NIWA, 1964;KONISHI, 1966). The electrical response from the entire nerve was recorded by means of an integrator (cf.…”

“…The recorded response vs. concentration curve displays a convex shape having a maximum at extremely low concentration. KONISHI (1966) suggested a hypothetical explanation for the mechanism of the specific receptor stimulation, in terms of an interfacial physiochemical model. The explanation was that the change of the electrokinetic potential of the receptor membrane, caused by adsorption of stimulus ions by the membrane, might determine the activity of the receptor system.…”

Chemoreception of the Lateral-Line Organ of an Aquatic Amphibian, Xenopus Laevis

“…of Xenopus. KONISHI (1966) later reported that Na+ solutions at much more dilute concentrations than those used in the present experiment affected the taste receptors in the mouth. The threshold concentration found in the ordinary frog was not very different from our results (KusANO, 1960).…”

“…Suppression by Na salts has already been observed in taste receptors in vertebrates: in fish (KONISHI, 1966), in frog (ZOTTERMAN, 1949;ANDERSON and ZOTTERMAN, 1950;KUSANO and SATO, 1957;SATO and KUSANO, 1960;YAMASHITA, 1963), and in mammals (PFAFFMANN, 1941;COHEN et al, 1955;PFAFFMANN, 1955). These results have been described as the effect of water, and the afferent fibers concerned are usually called water fibers.…”