Current injection and receptor-mediated excitation produce similar maximal firing rates in hypoglossal motoneurons.
Current injection and receptor-mediated excitation produce similar maximal firing rates in hypoglossal motoneurons.
复制标题
电流注射和受体介导的兴奋在舌下运动神经元中产生相似的最大放电率。
DOI：
10.1152/jn.00848.2015
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发表时间：
2016
影响因子：
2.5
通讯作者：
Fuglevand,AndrewJ
中科院分区：
文献类型：
--
作者：
Wakefield,HilaryE;Fregosi,RalphF;Fuglevand,AndrewJ
响应突触驱动而激活的运动神经元 (MN) 的最大放电率似乎远低于电流注射引起的放电率。与突触活动增加（但不是电流注入）相关的输入电阻的降低可能会减弱膜去极化的整体变化，从而限制尖峰频率输出。为了测试这个想法，我们在相同的细胞中记录了对电流注射和突触激活的最大放电反应。我们在新生大鼠中制备了 300 μm 的髓质切片，其中含有舌下 MN，并使用全细胞膜片钳电生理学记录其响应三角斜坡电流注射和谷氨酸受体介导的兴奋的最大放电率。高浓度谷氨酸的短暂压力脉冲导致显着的去极化、高发射率以及由于尖峰失活而暂时停止尖峰。在相同的细胞中，我们应用了电流钳方案，该方案近似于与谷氨酸应用相关的膜电位变化的时间过程，并且峰值电流水平足够大以引起尖峰失活。响应谷氨酸盐应用而获得的最大放电率的平均值 (SD) 与响应斜坡电流注入而获得的最大放电率的平均值 (SD) 几乎相同 [谷氨酸盐 47.1 ± 12.0 脉冲 (imp)/s，电流注入 47.5 ± 11.2 imp/s]，尽管与电流注入相比，谷氨酸盐应用期间的输入电阻减少了 40%。因此，这些数据表明，与受体介导的兴奋相关的输入阻力的降低本身并不限制 MN 的最大放电率反应。
The maximum firing rates of motoneurons (MNs), activated in response to synaptic drive, appear to be much lower than that elicited by current injection. It could be that the decrease in input resistance associated with increased synaptic activity (but not current injection) might blunt overall changes in membrane depolarization and thereby limit spike-frequency output. To test this idea, we recorded, in the same cells, maximal firing responses to current injection and to synaptic activation. We prepared 300 μm medullary slices in neonatal rats that contained hypoglossal MNs and used whole-cell patch-clamp electrophysiology to record their maximum firing rates in response to triangular-ramp current injections and to glutamate receptor-mediated excitation. Brief pressure pulses of high-concentration glutamate led to significant depolarization, high firing rates, and temporary cessation of spiking due to spike inactivation. In the same cells, we applied current clamp protocols that approximated the time course of membrane potential change associated with glutamate application and with peak current levels large enough to cause spike inactivation. Means (SD) of maximum firing rates obtained in response to glutamate application were nearly identical to those obtained in response to ramp current injection [glutamate 47.1 ± 12.0 impulses (imp)/s, current injection 47.5 ± 11.2 imp/s], even though input resistance was 40% less during glutamate application compared with current injection. Therefore, these data suggest that the reduction in input resistance associated with receptor-mediated excitation does not, by itself, limit the maximal firing rate responses in MNs.