Behavioral, Electrophysiological and Immunohistochemical Study on the Neuronal Plasticity of the Visual System in the Rat with Monocular Enucleation

在我们的一系列行为学和电生理实验中，我们已经证实，出生后早期的单眼摘除导致白化大鼠通过背外侧膝状体核(LGND)和上丘(SC)到同侧视皮层的扩展的非交叉视觉通路(扩展的UXVP)。在此基础上，本研究的目的是通过评估光栅视力来阐明扩展的UXVP的功能，并通过c-FOG免疫组织化学的方法研究扩展的UXVP的神经机制，得到以下结果。在垂直-水平分辨学习的行为学实验中，出生时单眼摘除(OEB)大鼠的UXVP的栅栏视力为0.73周/度，成熟期单眼摘除(OET)大鼠的UXVP的栅视敏度为0.44周/度，表明扩展的UXVP导致了OEB的高视觉分辨能力。在免疫组织化学实验中，采用图形视觉刺激的方法，探讨了刺激依赖诱导早期基因c-fos在UXVP神经元中表达的可行性。将50亩厚的冠状切片与绵羊Fos蛋白的一抗血清孵育，然后与生物素标记的兔抗羊二抗和亲和素生物素化的辣根过氧化物酶复合体孵育。硫酸镍铵对DAB反应有促进作用。在OEB大鼠扩张的UXVP中，在SC的灰质浅层(SGS)和视皮层(Vc)可见大量的Fos样免疫反应(FLI)细胞，而图形视觉刺激仅在OET大鼠的SGS和Vc中诱导出少量的FLI神经元。

In a series of our behavioral and electrophysiological experiments, it has been demonstrated that monocular enucleation in early postnatal days results in expanded uncrossed visual pathways (expanded UXVPs) to the ipsilateral visual cortex, both via the dorsal lateral geniculate nucleus (LGNd) and via the superior colliculus (SC) in the albino rat. The present study was then aimed to elucidate the function of the expanded UXVPs by evaluating the grating visual acuity and to investigate the neural mechanism of the expanded UXVPs by way of c-fog immunohistochemistry, and the following findings were obtained.1. In the behavioral experimet using a vertical-horizontal discrimination learning, the grating visual acuity of the UXVPs was 0.73 cycles/degree in the rat with monocular enucleation at birth (OEB) and 0.44 in the rat monocularly enucleated at maturity (OET), indicating that the expanded UXVPs results high visual resolution capacity in OEBs.2. In the immunohistochemical experiment, patterned visual stimulation was used to investigate the feasibility of stimulus-dependent induction of the immediate early gene c-fos in neurons of the UXVPs following callosal transection. The 50 mu m-thick coronal sections were incubated with the primary antiserum raised in sheep against the Fos protein, and then with biotinylated rabbit anti-sheep secondary antibody, and with the avidin biotinylated horseradish peroxidase complex. The DAB reaction was intensified with nickel ammonium sulfate. In the expanded UXVPs of the OEB rat, the Fos-like immunoreactive (FLI) cells were substantially detected in the stratum griseum superficiale (SGS) of the SC and the visual cortex (VC), whereas patterned visual stimulation induced only few FLI neurons in the SGS and the VC of the regular UXVPs of the OET rat,