Difference and relationship between plastic synapse of sensitive period and that of after effect in the visual cortex.

自1963年Wiesel和Hubel的开创性工作以来，已经提出(i)活动依赖机制和（ii）神经化学基础参与敏感期观察到的眼优势可塑性的调节。我们已经提出中枢去肾上腺素能系统作为主要的神经化学基础，在调节眼优势可塑性中起着至关重要的作用。最近的电镜研究表明，猫视觉皮层星形胶质细胞表达β -肾上腺素能受体。因此，我们认为去甲肾上腺素（NA）的作用可能部分由星形胶质细胞功能介导，未成熟的星形胶质细胞可能整合了活性依赖机制和神经化学基础。我们已经证明一种胶质毒素抑制了眼优势可塑性。这种神经胶质受累可能是敏感期可塑性所特有的，而不是后遗症。我们用适当的漂移来研究自波光栅的后效。17区50%的细胞出现了后遗症。后遗症发生的频率较低似乎取决于麻醉和麻痹的程度。以前已经证明，眼优势可塑性在麻醉和瘫痪状态下被冻结。虽然这些发现可能是相互关联的，但我们没有发现NA诱导后出现后效的细胞频率增加。对被剥夺单眼的猫的实验表明，被剥夺眼的条件反射没有引起正常眼的后效，说明后效突触在敏感期受到视觉环境的影响。

Since the pioneering work by Wiesel and Hubel in 1963, involvements of (i) the activity-dependent mechanism and (ii) the neurochemical basis, have been suggested in the regulation of the ocular doinance plasticity observed during the sensitive period. We have proposed that the central noradrenergic system plays a crucial role in the regulation of the ocular dominance plasticity as a major neurochemical basis. Recent electron microscopic studies showed that astrocytes in kitten visual cortex express beta-adrenergic receptors. Thus, we consider a possibility that the action of noradrenaline (NA) is partially mediated by the astrocytic function and immature astrocytes may integrate the activity-dependent mechanism and the neurochemical basis. We have shown that a gliotoxin suppressed the ocular dominance plasticity. This glial involvement may be unique for the sensitive period plasticity not for the aftereffect. We studied after effects using adequate drifting since wave grating.Fifty percent of cells in area 17 examined showed aftereffect. The lower frequency of aftereffect seems to depend on the anesthesia and paralysis. It has priviously been demonstrated that ocular dominance plasticity is freezed under anesthetized and paralyzed conditions. Although, these finding may be correlated each other, we could not detect the increase of frequency of cells showing aftereffect by the NA indusion. Experiments with the monocularly deprived kitten showed that the conditioning of the deprived eye never induced aftereffect of the normal eye, suggested that synapses of aftereffect are affected by visual environment during the sensitive period.