Sour taste is detected by type III taste receptor cells that generate membrane depolarization with action potentials in response to HCl applied to the apical membranes. The shape of action potentials in type III cells exhibits larger afterhyperpolarization due to activation of transient A-type voltage-gated K⁺ currents. Although action potentials play an important role in neurotransmitter release, the electrophysiological features of A-type K⁺ currents in taste buds remain unclear. Here, we examined the electrophysiological properties of A-type K⁺ currents in mouse fungiform taste bud cells using in-situ whole-cell patch clamping. Type III cells were identified with SNAP-25 immunoreactivity and/or electrophysiological features of voltage-gated currents. Type III cells expressed A-type K⁺ currents which were completely inhibited by 10 mM TEA, whereas IP₃R3-immunoreactive type II cells did not. The half-maximal activation and steady-state inactivation of A-type K⁺ currents were 17.9 ± 4.5 (n = 17) and − 11.0 ± 5.7 (n = 17) mV, respectively, which are similar to the features of Kv3.3 and Kv3.4 channels (transient and high voltage-activated K⁺ channels). The recovery from inactivation was well fitted with a double exponential equation; the fast and slow time constants were 6.4 ± 0.6 ms and 0.76 ± 0.26 s (n = 6), respectively. RT-PCR experiments suggest that Kv3.3 and Kv3.4 mRNAs were detected at the taste bud level, but not at single-cell levels. As the phosphorylation of Kv3.3 and Kv3.4 channels generally leads to the modulation of cell excitability, neuromodulator-mediated A-type K⁺ channel phosphorylation likely affects the signal transduction of taste.

酸味由 III 型味觉感受器细胞检测到，这些感受器细胞响应施加于顶膜的 HCl 产生膜去极化和动作电位。^{由于瞬态 A 型电压门控 K +}电流的激活，III 型细胞中的动作电位形状表现出更大的超极化后。尽管动作电位在神经递质释放中发挥重要作用，但味蕾中A 型 K ^{+电流的电生理特征仍不清楚。}在这里，我们使用原位全细胞膜片钳检查了小鼠蕈状味蕾细胞中 A 型 K ^{+电流的电生理特性。}III 型细胞被鉴定为具有 SNAP-25 免疫反应性和/或电压门控电流的电生理学特征。III 型细胞表达 A 型 K ⁺电流，该电流被 10 mM TEA 完全抑制，而 IP ₃ R3 免疫反应性 II 型细胞则不然。^{A型K +}电流的半最大激活和稳态失活分别为17.9 ± 4.5 (n = 17) 和− 11.0 ± 5.7 (n = 17) mV，与Kv3.3的特征相似和 Kv3.4 通道（瞬态和高电压激活的 K ⁺通道）。灭活后的回收率很好地符合双指数方程；快和慢时间常数分别为 6.4 ± 0.6 ms 和 0.76 ± 0.26 s (n = 6)。RT-PCR 实验表明，Kv3.3 和 Kv3.4 mRNA 在味蕾水平上检测到，但在单细胞水平上未检测到。由于Kv3.3和Kv3.4通道的磷酸化通常会导致细胞兴奋性的调节，因此神经调节剂介导的A型K ⁺通道磷酸化可能会影响味觉的信号转导。