Van Wilgenburg H, Njio K D, Belling G A, Van den Hoven S
Eur J Pharmacol. 1982 Oct 22;84(3-4):129-37. doi: 10.1016/0014-2999(82)90195-9.
The mean size of the synaptic vesicles in the nerve endings of the isolated rat diaphragm was significantly increased after incubation with the glucocorticoids prednisolone (10(-5) mol/l) and dexamethasone (2 X 10(-7) mol/l). The shape of the vesicles was also changed, i.e. they became rounder. Similar increases in the mean size of the diaphragm synaptic vesicles were seen when the rats were injected with prednisolone (i.p., 2 mg/kg) and dexamethasone (i.p., 50 micrograms/kg) 2-4 h previously. The amplitude of the miniature endplate potentials was also significantly increased in diaphragms isolated from rats which had been injected with prednisolone or with dexamethasone. Changes in frequency of the MEPPs were less marked after injection of prednisolone, but a significant increase was seen after injection of dexamethasone. It is concluded that relatively low concentrations of glucocorticoids have direct effects on the motor endplate in rat diaphragm both in vitro and in vivo. We tentatively suggest that presynaptic effects may contribute to the beneficial effect of corticosteroids in deficient neuromuscular transmission, e.g. in myasthenia gravis.
在与糖皮质激素泼尼松龙（10⁻⁵mol/L）和地塞米松（2×10⁻⁷mol/L）共同孵育后，分离出的大鼠膈肌神经末梢中突触小泡的平均大小显著增加。小泡的形状也发生了变化，即变得更圆。当大鼠在2 - 4小时前腹腔注射泼尼松龙（2mg/kg）和地塞米松（50μg/kg）时，膈肌突触小泡的平均大小也出现类似增加。在从注射过泼尼松龙或地塞米松的大鼠分离出的膈肌中，微小终板电位的幅度也显著增加。注射泼尼松龙后微小终板电位频率的变化不太明显，但注射地塞米松后则出现显著增加。结论是，相对低浓度的糖皮质激素在体外和体内对大鼠膈肌运动终板均有直接作用。我们初步认为，突触前效应可能有助于皮质类固醇对神经肌肉传递不足（如重症肌无力）的有益作用。
