The sodium glucose cotransporter 1 (SGLT1) has been proposed as a non-T1R glucosensor contributing to glucose taste. Studies have shown that the addition of NaCl at very weak concentrations to a glucose stimulus can enhance signaling in the gustatory nerves of mice and significantly lower glucose detection thresholds in humans. Here, we trained mice with (wild-type; WT) and without (knockout; KO) a functioning T1R3 subunit on a two-response operant detection task to differentially respond to the presence or absence of a taste stimulus immediately after sampling. After extensive training (∼40 sessions), KO mice were unable to reliably discriminate 2 M glucose+0.01 M NaCl from 0.01 M NaCl alone, but all WT mice could. We then tested WT mice on a descending array of glucose concentrations (2.0–0.03 M) with the addition of 0.01 M NaCl vs. 0.01 M NaCl alone. The concentration series was then repeated with glucose alone vs. water. We found no psychophysical evidence of a non-T1R taste transduction pathway involved in the detection of glucose. The addition of NaCl to glucose did not lower taste detection thresholds in WT mice, nor did it render the stimulus detectable to KO mice, even at 2 M. The proposed pathway must contribute to functions other than sensory-discriminative detection, at least when tested under these conditions. Detection thresholds were also derived for fructose and found to be 1/3 log lower than for glucose, but highly correlated ( = 0.88) between the two sugars, suggesting that sensitivity to these stimuli in this task was based on a similar neural process.

中文翻译：

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添加低钠不会增加野生型小鼠对葡萄糖的敏感性，或导致 T1R3 敲除小鼠检测到部分葡萄糖味觉

钠葡萄糖协同转运蛋白 1 (SGLT1) 已被提议作为一种有助于葡萄糖味觉的非 T1R 葡萄糖传感器。研究表明，在葡萄糖刺激物中添加极弱浓度的氯化钠可以增强小鼠味觉神经的信号传导，并显着降低人类的葡萄糖检测阈值。在这里，我们训练了具有（野生型；WT）和不具有（敲除型；KO）功能性 T1R3 亚基的小鼠进行双响应操作检测任务，以在采样后立即对味觉刺激的存在或不存在做出不同的反应。经过大量训练（~40 次）后，KO 小鼠无法可靠地区分 2 M 葡萄糖+0.01 M NaCl 与单独的 0.01 M NaCl，但所有 WT 小鼠都可以。然后，我们对 WT 小鼠进行了葡萄糖浓度递减排列 (2.0–0.03 M) 的测试，其中添加了 0.01 M 氯化钠，对比单独添加 0.01 M 氯化钠。然后用单独的葡萄糖与水重复该浓度系列。我们没有发现非 T1R 味觉转导途径参与葡萄糖检测的心理物理学证据。在葡萄糖中添加 NaCl 并不会降低 WT 小鼠的味觉检测阈值，也不会使得 KO 小鼠能够检测到刺激，即使在 2 M 下也是如此。所提出的途径必须有助于除感觉辨别检测之外的功能，至少在测试时是这样在这些条件下。还得出了果糖的检测阈值，发现其比葡萄糖低 1/3 log，但两种糖之间高度相关 (= 0.88)，表明在此任务中对这些刺激的敏感性基于类似的神经过程。