Giza B K, Scott T R
Department of Psychology, University of Delaware, Newark 19716.
Brain Res. 1991 Jun 7;550(2):247-56. doi: 10.1016/0006-8993(91)91325-u.
Amiloride is an inhibitor of passive sodium transport. Its application to taste receptors blocks inward sodium current, suppresses sodium-induced neural activity and reduces the perceived intensity of NaCl. We recorded taste-evoked responses of single neurons in the nucleus tractus solitarius (NTS) of the rat before and after the lingual application of amiloride to determine which neurons would be affected, the degree of the effect and the subsequent form of the neural code for sodium. Responses to all 7 stimuli that contained Na+ or Li+ were suppressed by amiloride. Activity evoked by the 8 other stimuli was unaltered. NTS neurons could be divided into 4 subsets according to their response profiles: Group 1 (salt-sugar), Group 2 (salt), Group 3 (salt-acid) and Group 4 (acid-salt-bitter). The entire effect of amiloride was discharged on cells in Groups 1 and 2; those in Groups 3 and 4 were unaffected. Following amiloride application, the neural code for sodium and lithium salts was highly similar to those for acids, bitter salts and quinine. Thus the activity of neurons in Groups 1 and 2 may be responsible for the distinction between 'saltiness' and sour-bitter tastes. The results imply that specific receptors are responsible for the recognition and transduction of sodium salts and that this specificity is maintained in the peripheral taste nerves to be manifested in the NTS.
氨氯吡咪是一种被动钠转运抑制剂。将其应用于味觉感受器可阻断内向钠电流，抑制钠诱导的神经活动，并降低对氯化钠的感知强度。我们记录了大鼠孤束核（NTS）中单个神经元在舌部应用氨氯吡咪前后的味觉诱发反应，以确定哪些神经元会受到影响、影响程度以及随后钠的神经编码形式。对所有7种含有Na+或Li+的刺激的反应均被氨氯吡咪抑制。其他8种刺激诱发的活动未改变。根据其反应特征，NTS神经元可分为4个亚组：第1组（盐 - 糖）、第2组（盐）、第3组（盐 - 酸）和第4组（酸 - 盐 - 苦）。氨氯吡咪的全部作用在第1组和第2组的细胞上释放；第3组和第4组的细胞未受影响。应用氨氯吡咪后，钠盐和锂盐的神经编码与酸、苦盐和奎宁的神经编码高度相似。因此，第1组和第2组神经元的活动可能是“咸味”与酸 - 苦味之间区别的原因。结果表明，特定的受体负责钠盐的识别和转导，并且这种特异性在外周味觉神经中得以维持，并在NTS中表现出来。
