Lundy R F, Pittman D W, Contreras R J
Department of Psychology, Florida State University, Tallahassee 32306-1270, USA.
Am J Physiol. 1997 Dec;273(6):R1923-31. doi: 10.1152/ajpregu.1997.273.6.R1923.
The effects of the epithelial Na+ channel antagonists amiloride and benzamil and the Na+/H+ exchange antagonist 5-(N,N-dimethyl)-amiloride (DMA)-Cl on the integrated responses of the chorda tympani nerve to 30, 75, 150, 300, and 500 mM concentrations of NaCl, KCl, and NH4Cl were assessed in male Sprague-Dawley rats. Based on evidence from other systems, 1 and 25 microM amiloride and benzamil were chosen to selectively inhibit epithelial Na+ channels and 1 microM DMA was chosen to selectively inhibit Na+/H+ exchange. When added to stimulating salt solutions, amiloride, benzamil, and DMA were each effective in inhibiting responses to all three salts. The degree of inhibition varied with drug, salt, and salt concentration, but not drug dose. Amiloride suppressed NaCl responses to a greater degree than KCl and NH4Cl responses, whereas DMA suppressed NH4Cl responses to a greater degree than NaCl and KCl responses. In all but one case (25 microM amiloride added to KCl), drug suppression of taste nerve responses decreased with an increase in salt concentration. The present results suggest that 1) epithelial Na+ channels in rat taste receptor cells may play a role in KCl and NH4Cl taste transduction; 2) a Na+/H+ exchange protein may be present in taste receptor cells, representing a putative component, in addition to epithelial Na+ channels, in salt taste transduction; and 3) salt taste detection and transduction may depend on the utilization of a combination of common and distinct transcellular pathways.
在雄性斯普拉格-道利大鼠中，评估了上皮钠离子通道拮抗剂阿米洛利和苄米洛利以及钠氢交换拮抗剂5-(N,N-二甲基)-阿米洛利（DMA）-Cl对鼓索神经对30、75、150、300和500 mM浓度的氯化钠、氯化钾和氯化铵的综合反应的影响。基于其他系统的证据，选择1和25 microM的阿米洛利和苄米洛利来选择性抑制上皮钠离子通道，选择1 microM的DMA来选择性抑制钠氢交换。当添加到刺激性盐溶液中时，阿米洛利、苄米洛利和DMA均能有效抑制对所有三种盐的反应。抑制程度随药物、盐和盐浓度而变化，但与药物剂量无关。阿米洛利对氯化钠反应的抑制程度大于对氯化钾和氯化铵反应的抑制程度，而DMA对氯化铵反应的抑制程度大于对氯化钠和氯化钾反应的抑制程度。除一种情况（将25 microM阿米洛利添加到氯化钾中）外，药物对味觉神经反应的抑制作用随盐浓度的增加而降低。目前的结果表明：1）大鼠味觉受体细胞中的上皮钠离子通道可能在氯化钾和氯化铵味觉转导中起作用；2）味觉受体细胞中可能存在钠氢交换蛋白，这是除上皮钠离子通道外盐味觉转导中的一个假定成分；3）盐味觉检测和转导可能取决于共同和不同的跨细胞途径的组合的利用。
