カエル舌咽神経のNa塩味覚刺激に対する相動性応答の性質

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The frog glossopharyngeal nerve responds transiently to relatively high concentrations of Na-salts after rinsing the tongue with 1mM NaCl. In the present study, the properties of the phasic responses of the frog glossopharyngeal nerve to Na-salts were investigated. Cross-adaptation experiments between NaCl and LiCl indicate that NaCl and LiCl were very similar to each other. This is in agreement with the fact that LiCl also gives rise to a good salty in humans. The order of effectiveness of Na-salts was NaCl≒Na acetate (NaAc)>Na gluconate (NaGlu). We found that gluconate^- weakly inhibited the phasic response to Na^+. The modulation by gluconate^-was specific to the phasic response to Na^+, because NaAc and NaGlu have a similar effect on phasic responses to quinine-HCl. Amiloride, an epithelial sodium channel broker, did not affect phasic responses to NaCl at 1.5 min after application of amiloride to the tongue, suggesting that amiloride-sensitive Na^+ channels in the apical membrane are not involved in phasic reponses to Na-salts in the frog glossopharyngeal nerve. Unitary impulses from single sensory units were recorded using the suction electrode method (Kitada, 1978). The latency between onset of stimulation and appearance of the first impulses elicited by 100mM NaCl was average 100 msec. Since the time required for antidromic conduction from the impulse initiation site to the recording site was very short, about 2.4 msec (Sato et al., 1987), it was suggested that the latency obtained here was close to the time between the arrival of the chemical stimulus to the apical membrane and the first impulse in taste fibers. The long latency of impulses in responses to NaCl suggests that cation-channels in the apical membrane are not involved in NaCl taste reception responsible for the phasic response.
2007-12-20

カエル舌咽神経のNa塩味覚刺激に対する相動性応答の性質

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