Brandstätter J H, Meinertzhagen I A
Neuroscience Institute, Dalhousie University, Halifax, NS, Canada.
Proc Natl Acad Sci U S A. 1995 Mar 28;92(7):2677-81. doi: 10.1073/pnas.92.7.2677.
When a housefly, Musca domestica, is subject to cold exposure (0 degrees C for 24 hr), a number of obvious changes are seen in the first optic neuropil, or lamina, beneath the compound eye. In particular, the number of afferent photoreceptor synapses declines by about 30%. This loss is dramatically restored after warm recovery at 23 degrees C for 24 hr. Synapses disappear at an average rate of 2-3/hr during cold exposure and reappear at a maximal rate of more than 20/hr during the first 2 hr of warm recovery. Thereafter their number temporarily overshoots control values, to increase at 6 hr of warm recovery to 60% above their cold-exposed minimum. The number subsequently returns more or less to normal. These changes demonstrate the lability of synaptic sites under these conditions, with individual sites forming and disappearing rapidly. The changes also interrupt the close correlation between synaptic number and the surface area of the receptor terminal, a correlation that normally conserves synaptic spacing density. The density is preserved during cold exposure but increases during warm recovery at a time when the addition of newly formed synapses exceeds the slower increase in receptor terminal size.
当家蝇（Musca domestica）遭受冷暴露（0摄氏度，持续24小时）时，在复眼下方的第一视觉神经纤维层，即神经层中会出现一些明显的变化。特别是，传入光感受器突触的数量减少了约30%。在23摄氏度下温暖恢复24小时后，这种损失会显著恢复。在冷暴露期间，突触以平均每小时2 - 3个的速率消失，而在温暖恢复的最初2小时内，突触以超过每小时20个的最大速率重新出现。此后，它们的数量暂时超过对照值，在温暖恢复6小时时增加到比冷暴露时的最小值高出60%。随后数量或多或少恢复正常。这些变化表明在这些条件下突触位点的不稳定性，单个位点迅速形成和消失。这些变化还中断了突触数量与受体末端表面积之间的紧密相关性，这种相关性通常能保持突触间距密度。在冷暴露期间密度得以保持，但在温暖恢复期间，当新形成的突触增加超过受体末端大小较慢的增加时，密度会增加。
