The rostral nucleus of the solitary tract (rNST) serves as the first central relay in the gustatory system. In addition to synaptic interactions, central processing is also influenced by the ion-channel composition of individual neurons. For example, voltage-gated K⁺ channels such as I_A can modify the integrative properties of neurons. I_A currents are prevalent in rNST projection cells but are also found to a lesser extent in GABAergic interneurons. However, characterization of the kinetic properties of I_A, the molecular basis of these currents as well as the consequences of I_A on spiking properties of identified rNST cells is lacking. Here we show that I_A in rNST GABAergic (G+) and non-GABAergic (G-) neurons share a common molecular basis. In both cell types, there was a reduction in I_A following treatment with the specific Kv4 channel blocker AmmTX3. However, the kinetics of activation and inactivation of I_A in the two cell types were different with G+ neurons having significantly more negative half-max activation and inactivation values. Likewise, under current clamp, G- cells had significantly longer delays to spike initiation in response to a depolarizing stimulus preceded by a hyperpolarizing pre-pulse. Computational modeling and dynamic clamp suggest that differences in the activation half-max may account for the differences in delay. We further observed evidence for a window current under both voltage clamp and current clamp protocols. We speculate that the location of Kv4.3 channels on dendrites, together with a window current for I_A at rest, serves to regulate excitatory afferent inputs.

中文翻译：

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GABA 能和非 GABA 能 rNST 神经元中的 Kv4 通道表达和动力学

孤束的延髓核 (rNST) 是味觉系统的第一个中枢。除了突触相互作用之外，中央处理还受到单个神经元的离子通道组成的影响。例如，电压门控 K ⁺通道如 I _A可以修改神经元的综合特性。I _A电流在 rNST 投射细胞中很普遍，但在 GABA 能中间神经元中也发现较少。然而，缺乏I _A的动力学特性、这些电流的分子基础以及 I _A对已识别 rNST 细胞的尖峰特性的影响的表征。这里我们证明 I _A在 rNST 中 GABA 能 (G+) 和非 GABA 能 (G-) 神经元共享一个共同的分子基础。在两种细胞类型中，用特定的 Kv4 通道阻滞剂 AmmTX3 处理后 I _A都有所降低。然而，我的激活和失活的动力学_一在两种细胞类型中，G+ 神经元具有显着更多的负半最大激活和失活值。同样，在电流钳下，G 细胞响应于超极化预脉冲之前的去极化刺激具有明显更长的延迟来启动尖峰。计算建模和动态钳位表明激活半最大值的差异可能是延迟差异的原因。我们进一步观察到电压钳和电流钳协议下窗口电流的证据。我们推测 Kv4.3 通道在树突上的位置，以及静止时I _A的窗口电流，用于调节兴奋性传入输入。