Biomedical subjects
Publications and source records attributed to F Sakudo.
Stimulation of the frog tongue with various salts produced changes in epithelial potential of the tongue, accompanied by changes in gustatory nerve activity. Both changes varied similarly according to the stimulus. The results indicate that cation transport in the lingual epithelium is involved in gustation.
1. Open-circuit potential difference and short-circuit current across the frog tongue epithelium in response to glycinamide and glycylglycinamide were investigated. 2. Response to both of these amides were larger than the responses produced by glycine, glycylglycine and NaCl, and were independent of Na+ in the mucosal medium but dependent on H+ in the stimulus. 3. The relationships of the magnitudes of both response to the stimulus were similar to that in the taste nerve. 4. The results indicate that H+-dependent transport of these amides is related to taste reception in frogs.
Isolated dorsal epithelium of the frog tongue elicited transepithelial NaCl and water responses across the tissue when NaCl was added to or removed from the adapting Ringer solution in the mucosal surface, respectively. The NaCl response which was a negative polarization in the mucosa with respect to the serosa was associated with a decrease in resistance across the tissue, whereas the water response which was a positive polarization was associated with an increase in the resistance. The decrease and increase in the tissue resistance remained unchanged by various polarizations of the transepithelial potential difference across the tissue. Characteristics of the NaCl and water responses were similar in many respects to those in the taste cells and nerves of frogs. Thus the NaCl and water responses may relate to taste reception.
Electrical properties of the frog tongue epithelium were compared to those of skin and bladder, which have active sodium transport. During perfusion with Ringer solution, the potential difference across the tongue epithelium was negligible, unlike those of the skin and bladder. NaCl stimulation of the tongue epithelium produced a response with a polarity opposite to that of the skin and bladder. The response profile of the tongue epithelium except for the polarity resembled that of other tissues. In conclusion, the NaCl response of the tongue epithelium is independent of active sodium transport and instead occurs by passive transport, which may influence taste reception.
This study demonstrated the electrophysiological characteristics of the dorsal surface of the frog tongue in vivo. The results were as follows: 1. Epithelial potential of the tongue surface was abolished with respect to the grounded leg muscle when the tongue was adapted to 30 mM NaCl solution among various NaCl concentrations. In the 30 mM NaCl-adaptation, magnitude of integrated impulse discharges simultaneously obtained from the glossopharyngeal nerve was lowest. Thus, this solution was mainly used as the adapting solution during the experiments. 2. Stimulation of the tongue with NaCl, acetic acid, quinine-HCl, and sucrose produced changes in the epithelial potential and the integrated impulse discharges (epithelial and neural response, respectively). Both responses showed inherent patterns to the stimulus quality and concentration. 3. The epithelial response to NaCl was negative to the ground, and its magnitude was increased with decreasing NaCl in the adapting solution and decreased with increasing NaCl. These influences were similar to those of the neural response. 4. The relationship between the epithelial response and the stimulus NaCl was in approximate agreement with that of the neural response. 5. Characteristics of the epithelial response to NaCl coincided with those obtained from the isolated dorsal epithelium of the tongue in vitro, which were associated with a decrease in resistance across the tissue. 6. Ouabain had no influence on both the epithelial and neural responses to NaCl, but local anesthetics reversibly inhibited them. The inhibition by local anesthetics was slower and smaller in the epithelial response than in the neural response. 7. Salts similar to NaCl also produced epithelial and neural responses, but their magnitudes inversely depended on an inherent hydrated cation size of the salts in aqueous solution. Based on the results, it is concluded that the epithelial response to NaCl is produced by sodium transport across the dorsal epithelium of the tongue, and the transport may relate to the mechanism of salty sensation.
Transepithelial response across frog tongue epithelium induced by NaCl was compared with that induced by other salts and saccharides. All responses to salts including NaCl were negative in the mucosa to the grounded serosa and were associated with decreased tissue resistance, whereas those to saccharides were positive with increased tissue resistance. The response to salts varied in pattern and magnitude with variation in stimulus quality. The results indicate that the salt induced response is mediated by cation movement through the tissue and is implicated in taste reception.
1. Dorsal epithelium of the frog tongue produced a change in potential difference across the tissue in response to removal of NaCl from the adapting Ringer solution on the mucosa. 2. The response was not caused by an osmotic decrease in the stimulus, and its profile was in many respects similar to that of the receptor potential in frog taste cells. 3. In conclusion, the response may influence or modify water reception in frogs.
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Stimulation with hypotonic NaCl Ringer solution produced a change in potential across the epithelium, which was not caused by decreased osmotic pressure. The potential profile resembled the receptor potential of frog taste cells and so may be related to water reception.
Application of NaCl to the frog tongue produced a sodium influx through the dorsal epithelium. The flux was distinctly faster through those of the palatal epithelium and the skin, and may influence taste reception in frogs.
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Acid stimulation produced a change in trans-epithelial potential difference across isolated dorsal epithelium of frog tongue. The responses to acetic acid, tartaric acid and citric acid were significantly greater than those to hydrochloric acid and nitric acid at the same pH. Metabolic inhibitors had no effect on the response, but local anaesthetics reversibly depressed it. The induced response was associated with a decrease in tissue resistance. Positive polarization on the mucosa increased the response, which was decreased or reversed under negative polarization. These responses may be caused by diffusion of H-ions through the tissue, and may influence sour reception in the frog.
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Explore the source record for details and available documents.
Explore the source record for details and available documents.
Stimulation of the bullfrog tongue with taste chemicals produced a slow change in transepithelial potential difference across the dorsal epithelium. The potential profile was in many respects similar to that of the intracellularly recorded potential changes in taste cells and to the activity of taste fibers in frogs.