Yokota Tatsuko, Katakura Nubuo, Morita Takumi, Matsunaga Tomoko, Hiraba Katsunari
Department of Physiology, School of Dentistry, Aichi-Gakuin University, Nagoya, Japan.
Physiol Rep. 2020 May;8(10):e14443. doi: 10.14814/phy2.14443.
It is crucial for animals to discriminate between palatable (safe) and aversive (toxic) tastants. The mechanisms underlying neuronal discrimination of taste stimuli remain unclear. We examined relations between taste response properties (spike counts, response duration, and coefficient of variation [CV]) and location of taste-sensitive neurons in the pontine parabrachial nucleus (PBN). Extracellular single units' activity in the PBN of Wistar rats was recorded using multibarrel glass micropipettes under urethane anesthesia. Forty taste-sensitive neurons were classified as NaCl (N)-best (n = 15), NaCl/HCl (NH)-best (n = 14), HCl (H)-best (n = 8), and sucrose (S)-best (n = 3) neurons. The net response to NaCl (15.2 ± 2.3 spikes/s) among the N-best neurons was significantly larger than that among the NH-best (4.5 ± 0.8 spikes/s) neurons. The response duration (4.5 ± 0.2 s) of the N-best neurons to NaCl was significantly longer than that of the NH-best (2.2 ± 0.3 s) neurons. These differences in the spike counts and the response durations between the two neuronal types in the PBN were similar to that previously reported in the rostral nucleus of the solitary tract (rNST). The CVs in the N-best and the NH-best neurons were significantly smaller in the PBN than those in the rNST. Histologically, most N-best neurons (12/13, 92%) were localized to the medial region, while NH-best neurons (11/13, 85%) were primarily found within the brachium conjunctivum. These results suggest that NaCl-specific taste information is transmitted by two distinct neuronal groups (N-best and NH-best), with different taste properties and locations within rNST to PBN tractography. Future studies on the higher order nuclei for taste could reveal more palatable and aversive taste pathways.
动物区分美味（安全）和厌恶（有毒）味觉刺激至关重要。神经元对味觉刺激进行区分的潜在机制仍不清楚。我们研究了味觉反应特性（峰计数、反应持续时间和变异系数[CV]）与脑桥臂旁核（PBN）中味觉敏感神经元位置之间的关系。在乌拉坦麻醉下，使用多管玻璃微电极记录Wistar大鼠PBN中细胞外单个单位的活动。40个味觉敏感神经元被分类为对氯化钠（N）反应最佳（n = 15）、对氯化钠/盐酸（NH）反应最佳（n = 14）、对盐酸（H）反应最佳（n = 8）和对蔗糖（S）反应最佳（n = 3）的神经元。N反应最佳神经元对氯化钠的净反应（15.2±2.3个峰/秒）显著大于NH反应最佳神经元（4.5±0.8个峰/秒）。N反应最佳神经元对氯化钠的反应持续时间（4.5±0.2秒）显著长于NH反应最佳神经元（2.2±0.3秒）。PBN中这两种神经元类型在峰计数和反应持续时间上的差异与先前在孤束吻侧核（rNST）中报道的相似。PBN中N反应最佳和NH反应最佳神经元的CV显著小于rNST中的CV。组织学上，大多数N反应最佳神经元（12/13，92%）位于内侧区域，而NH反应最佳神经元（11/13，85%）主要位于结合臂内。这些结果表明，氯化钠特异性味觉信息由两个不同的神经元群体（N反应最佳和NH反应最佳）传递，它们在rNST到PBN的神经束造影中具有不同的味觉特性和位置。未来对味觉高阶核的研究可能会揭示更多美味和厌恶味觉通路。
