Shao M, Popratiloff A, Yi J, Lerner A, Hirsch J C, Peusner K D
Department of Anatomy and Regenerative Biology, George Washington University Medical Center, 2300 I Street Northwest, Washington, DC 20037, USA.
Neuroscience. 2009 Jul 21;161(4):988-1007. doi: 10.1016/j.neuroscience.2009.04.027. Epub 2009 Apr 15.
Vestibular compensation refers to the behavioral recovery after a unilateral peripheral vestibular lesion. In chickens, posture and balance deficits are present immediately following unilateral vestibular ganglionectomy (UVG). After three days, most operated chickens begin to recover, but severe deficits persist in others. The tangential nucleus is a major avian vestibular nucleus whose principal cells are vestibular reflex projection neurons. From patch-clamp recordings on brain slices, the percentage of spontaneous spike firing principal cells, spike discharge rate, ionic conductances, and spontaneous excitatory postsynaptic currents (sEPSCs) were investigated one and three days after UVG. Already by one day after UVG, sEPSC frequency increased significantly on the lesion side, although no differences were detected in the percentage of spontaneous spike firing cells or discharge rate. In compensated chickens three days after UVG, the percentage of spontaneous spike firing cells increased on the lesion side and the discharge rate increased bilaterally. In uncompensated chickens three days after UVG, principal cells on the lesion side showed increased discharge rate and increased sEPSC frequency, whereas principal cells on the intact side were silent. Typically, silent principal cells exhibited smaller persistent sodium conductances and higher activation thresholds for the fast sodium channel than spiking cells. In addition, silent principal cells on the intact side of uncompensated chickens had larger dendrotoxin-sensitive potassium conductance, with a higher ratio of Kv1.1 surface/cytoplasmic expression. Increased sEPSC frequency in principal cells on the lesion side of uncompensated chickens was accompanied by decreased Kv1.2 immunolabeling of presynaptic terminals on principal cell bodies. Thus, both intrinsic ionic conductances and excitatory synaptic inputs play crucial roles at early stages after lesions. Unlike the principal cells in compensated chickens which showed similar percentages of spontaneous spike firing cells, discharge rates, and sEPSC frequencies bilaterally, principal cells in uncompensated chickens displayed gross asymmetry in these properties bilaterally.
前庭代偿是指单侧外周前庭损伤后的行为恢复。在鸡中，单侧前庭神经节切除术（UVG）后立即出现姿势和平衡缺陷。三天后，大多数接受手术的鸡开始恢复，但其他鸡仍存在严重缺陷。切向核是鸟类主要的前庭核，其主要细胞是前庭反射投射神经元。通过对脑片进行膜片钳记录，研究了UVG后1天和3天自发放电主细胞的百分比、放电率、离子电导和自发兴奋性突触后电流（sEPSC）。UVG后1天，损伤侧的sEPSC频率显著增加，尽管在自发放电细胞的百分比或放电率方面未检测到差异。UVG后3天，在已代偿的鸡中，损伤侧自发放电细胞的百分比增加，双侧放电率增加。UVG后3天，在未代偿的鸡中，损伤侧的主细胞放电率增加，sEPSC频率增加，而完整侧的主细胞无放电。通常，无放电的主细胞比有放电的细胞表现出更小的持续性钠电导和更高的快速钠通道激活阈值。此外，未代偿鸡完整侧无放电的主细胞具有更大的树突毒素敏感钾电导，Kv1.1表面/细胞质表达比例更高。未代偿鸡损伤侧主细胞中sEPSC频率增加，同时主细胞体上突触前终末的Kv1.2免疫标记减少。因此，内在离子电导和兴奋性突触输入在损伤后的早期阶段都起着关键作用。与已代偿鸡的主细胞不同，其双侧自发放电细胞的百分比、放电率和sEPSC频率相似，未代偿鸡的主细胞在这些特性上双侧表现出明显的不对称。
