Physiological and anatomical observations of the neural integrator in compensations of sensory organs

前庭代偿归因于前庭中枢神经网络的功能和结构重组，但其确切机制尚不清楚。c-Fos蛋白在正常状态下表达非常有限，在外界刺激后迅速出现，因此被用作神经元激活的标志物。先前的报道调查了单侧迷路切除术后大鼠和豚鼠的c-Fos表达，但没有在小鼠脑干中进行。我们发现，小鼠单侧迷路切除后，双侧前庭内侧核（MVe）、双侧脊髓前庭核（SpVe）、对侧前庭舌下核（PrH）和对侧下橄榄核（IO）与其他物种一样被激活。视觉系统的注视机制抑制前庭源性眼震（视觉抑制）是众所周知的。一般认为，浦肯野细胞编码视网膜滑移并控制水平前庭-眼反射的增益。以前的报道表明，小叶的病变消除了视觉抑制。然而，视觉抑制的确切机制尚不完全清楚。我们记录了浦肯野细胞中缺乏谷氨酸受体δ 2亚基的突变小鼠的视觉抑制，以研究谷氨酰胺能系统在VOR控制中的作用。眼球运动被电脑捕捉并分析。将瞳孔拟合为椭圆，并利用椭圆的形状和方向计算眼球水平角运动（Iwashita et al. 2001）。在GluR δ -2（-/-）小鼠中，速度降低很小（10%），在光线下没有变化甚至增加。上述结果提示，离子营养型谷氨酸受体介导的平行纤维输入到絮状浦肯野细胞在前庭眼球震颤的视觉抑制中起重要作用。

Vestibular compensation is attributed to functional and structural reorganization of neural networks in the central vestibular system, but its precise mechanism is still not clear. c-Fos protein is used as a marker of neuronal activation, because of its very limited expression in the normal state and rapid appearance after external stimulation. Previous reports, investigating c-Fos expression after unilateral labyrinthectomy were made in rats and guinea pigs, but not in the mouse brainstem. We elucidated, after unilateral labyrinthectomy in mice, the bilateral medial vestibular nucleus (MVe), bilateral spinal vestibular nucleus (SpVe), contralateral prepositus hypoglossal nucleus (PrH), and contralateral inferior olive nucleus (IO) were activated like in other species.It is well known that the fixating mechanism of visual system suppress nystagmus of vestibular origin(visual suppression). And it is generally assumed that floccular Purkinje cells encodes retinal slip and controls the gain of the horizontal vestibulo-ocular reflex. Previous reports showed that lesions in the flocculus abolish visual suppression. However the precise mechanism of the visual suppression is not completely understood. We recorded the visual suppressions in mutant mice deficient in the delta 2 subunit of the ionotrphhic glutamate receptor (GluR delta-2) in Purkinje cells to investigate the role of glutaminergic system on the control of VOR. Eye movements were captured and analyzed by a computer. The pupil was fitted as an ellipse and the horizontal eye angular movement was calculated using the shape and direction of ellipse (Iwashita et al. 2001). In GluR delta-2 (-/-)mice the velocity was reduced very little (10 %), no change or even increased in light. These results suggest that the parallel fiber input to floccular Purkinje cells mediated by ionotrophic glutamate receptor play important roles in the visual suppression of the vestibular nystagmus.