Beaulieu C, Colonnier M
Département d'Anatomie, Faculté de Médecine, Université Laval, Québec, Canada.
J Comp Neurol. 1988 Aug 15;274(3):347-56. doi: 10.1002/cne.902740305.
A recent quantitative analysis of cat visual cortex has demonstrated that the numerical density (Nv) of symmetrical synaptic contacts formed by boutons containing flat vesicles (FS synapses) is nearly twice as large in animals raised in isolation (impoverished condition: IC) as in animals raised in a colony (enriched condition: EC). Although some FS synapses have been shown to be cholinergic there is evidence that many, indeed the vast majority, are GABAergic. In order to estimate whether the change in the Nv of FS contacts was accompanied by a change in the number of boutons containing GABA, we have incubated sections of tissue from both groups of animals in an antiserum for GAD. In spite of the large increase in the number of FS contacts in impoverished cortex, we saw no obvious change in the apparent amount of labelled GAD terminals. In retrospect we realized that though the amount of labelled GAD terminals might reasonably be expected to reflect the number of F-boutons, it might not correspond so closely to the number of contacts formed by these boutons (which is what we had measured in the previous study): The richness of the environment could conceivably affect the number of contacts formed by the F-boutons without affecting the number of boutons! We thus extended our study by estimating the number of F-boutons in the two conditions. For the total cortical thickness, the Nv of F-boutons is only 17% lower (P less than .05) in enriched than in impoverished cats. The diameter of the boutons is 6% larger (P less than .001) in the enriched cortex. Because the F-boutons become fewer in number as they become larger in size, the total percentage volume occupied by these boutons does not change between the two experimental conditions. We conclude that this is the reason why there appears to be no change in the general amount of GAD label between the two groups of cats. More importantly, since the Nv of neurons is also 17% lower in enriched cortex, the number of F-boutons per neuron (and presumably the total number of F-boutons in the visual area) actually remains unchanged. In contrast, the previous study showed that the number of FS contacts per neuron is significantly decreased in enriched cortex. It follows that the number of contacts formed by each bouton must be altered.(ABSTRACT TRUNCATED AT 400 WORDS)
最近对猫视觉皮层的一项定量分析表明，由含有扁平囊泡的终扣形成的对称突触接触的数值密度（Nv），在隔离饲养的动物（贫乏条件：IC）中几乎是群体饲养动物（丰富条件：EC）的两倍。尽管一些FS突触已被证明是胆碱能的，但有证据表明，许多（实际上是绝大多数）是γ-氨基丁酸能的。为了估计FS接触的Nv变化是否伴随着含有γ-氨基丁酸的终扣数量的变化，我们用抗谷氨酸脱羧酶（GAD）血清孵育了两组动物的组织切片。尽管贫乏皮层中FS接触的数量大幅增加，但我们并未看到标记的GAD终末的表观量有明显变化。事后我们意识到，虽然标记的GAD终末的量可能合理地预期反映F终扣的数量，但它可能与这些终扣形成的接触数量（这是我们在先前研究中测量的）并不那么紧密对应：可以想象，环境的丰富程度可能会影响F终扣形成的接触数量，而不影响终扣的数量！因此，我们通过估计两种条件下F终扣的数量来扩展我们的研究。对于整个皮层厚度，丰富条件下的猫的F终扣的Nv仅比贫乏条件下的低17%（P小于0.05）。丰富皮层中的终扣直径大6%（P小于0.001）。由于F终扣随着尺寸变大数量减少，这些终扣所占的总体积百分比在两种实验条件下没有变化。我们得出结论，这就是两组猫之间GAD标记的总量似乎没有变化的原因。更重要的是，由于丰富皮层中神经元的Nv也低17%，每个神经元的F终扣数量（大概也是视觉区域中F终扣的总数）实际上保持不变。相比之下，先前的研究表明，丰富皮层中每个神经元的FS接触数量显著减少。由此可见，每个终扣形成的接触数量必定发生了改变。（摘要截选至400字）
