Smith J E, Reese T S
J Exp Biol. 1980 Dec;89:19-29. doi: 10.1242/jeb.89.1.19.
Aldehyde fixation continues to be useful to prepare synapses for freeze-fracture, but it may increase the rate of transmitter release. The effects of different aldehyde fixatives on spontaneous quantal release (m.e.p.p.s), and on the corresponding synaptic vesicle exocytosis at frog nerve-muscle synapses were investigated with the hope of finding a way to minimize side effects of fixation. Increases in m.e.p.p.s of up to 50 S-1 occurred during fixation, despite the species of aldehyde used in the fixative, and this fixative effect decreased only slightly as aldehyde concentration was increased. Increases in m.e.p.p frequency were not blocked by tetrodotoxin, by lowering external calcium and raising external magnesium concentration, or by lowering the total osmotic strength of the fixative. The smallest increase in m.e.p.p. frequency was in 3% glutaraldehyde and corresponded to the lowest level of synaptic vesicle exocytosis seen by freeze-fracture, 0.15 per micrometers of active zone. The effects of aldehyde fixation on m.e.p.p. frequency and synaptic vesicle exocytosis could not be avoided, but this study suggests how its effect on morphological changes in synapses might be minimized.
醛类固定剂对于为冷冻断裂制备突触仍然有用，但它可能会增加递质释放的速率。研究了不同醛类固定剂对青蛙神经-肌肉突触自发量子释放（微小终板电位）以及相应突触小泡胞吐作用的影响，希望找到一种方法将固定的副作用降至最低。在固定过程中，无论固定剂中使用的醛类种类如何，微小终板电位最多增加50%，并且随着醛浓度的增加，这种固定效应仅略有下降。微小终板电位频率的增加不受河豚毒素、降低细胞外钙浓度和提高细胞外镁浓度或降低固定剂的总渗透压强度的影响。微小终板电位频率增加最小的是在3%的戊二醛中，这与冷冻断裂观察到的突触小泡胞吐作用的最低水平相对应，即每微米活性区0.15次。醛类固定对微小终板电位频率和突触小泡胞吐作用的影响无法避免，但这项研究表明了如何将其对突触形态变化的影响降至最低。
