Westcott S L, Powers R K, Robinson F R, Binder M D
Department of Physiology and Biophysics, University of Washington, School of Medicine, Seattle 98195, USA.
Exp Brain Res. 1995;107(1):1-8. doi: 10.1007/BF00228010.
We applied supramaximal, repetitive stimulation to the lateral vestibular nucleus (Deiters' nucleus, DN) at 200 Hz to evoke stead-state synaptic potentials in ipsilateral triceps surae motoneurons of the cat. The effective synaptic currents underlying these potentials were measured using a modified voltage-clamp technique. The steady-state effective synaptic currents evoked by activating DN were generally small and depolarizing (mean 2.5 +/- 2.6 nA). DN stimulation generated hyperpolarizing synaptic currents in 2 of the 34 triceps motoneurons studied. The effective synaptic currents from DN tended to be larger in putative type F motoneurons than in putative type S cells (type F mean 3.0 +/- 3.1 nA; type S mean 1.8 +/- 1.0 nA). There was a statistically significant difference between the inputs to putative type FF and putative type S motoneurons (mean difference 2.8 nA, t = 2.87, P < 0.01). The synaptic input from DN to medial gastrocnemius motoneurons had approximately the same amplitude as that from homonymous Ia afferent fibers. However, the distribution of DN input with respect to putative motor unit type was the opposite of that previously reported for Ia afferent input. Thus, the synaptic input from DN might act to compress the range of recruitment thresholds within the motoneuron pool and thereby increase the gain of its input-output function.
我们以200 Hz的频率对猫的外侧前庭核（Deiters核，DN）施加超强重复刺激，以诱发同侧腓肠三头肌运动神经元的稳态突触电位。使用改良的电压钳技术测量这些电位背后的有效突触电流。激活DN诱发的稳态有效突触电流通常较小且呈去极化（平均2.5±2.6 nA）。在所研究的34个腓肠三头肌运动神经元中，有2个神经元在DN刺激下产生了超极化突触电流。来自DN的有效突触电流在假定的F型运动神经元中往往比在假定的S型细胞中更大（F型平均3.0±3.1 nA；S型平均1.8±1.0 nA）。假定的FF型和假定的S型运动神经元的输入之间存在统计学上的显著差异（平均差异2.8 nA，t = 2.87，P < 0.01）。从DN到内侧腓肠肌运动神经元的突触输入幅度与来自同名Ia传入纤维的幅度大致相同。然而，DN输入相对于假定运动单位类型的分布与先前报道的Ia传入输入的分布相反。因此，来自DN的突触输入可能起到压缩运动神经元池内募集阈值范围的作用，从而增加其输入-输出功能的增益。
