Lnenicka G A, Atwood H L, Marin L
J Neurosci. 1986 Aug;6(8):2252-8. doi: 10.1523/JNEUROSCI.06-08-02252.1986.
In vivo stimulation of a relatively "silent" phasic crayfish motoneuron changes the ultrastructure of its synaptic terminals to a more tonic phenotype. The closer muscle of the crayfish claw is supplied by only 2 excitatory motoneurons, one of which is phasic and the other tonic. The ultrastructures of conditioned phasic, unconditioned phasic, and tonic motor terminals were compared. The terminals of the tonic motor axon were larger in cross-sectional area, had larger mitochondria, greater synaptic contact area, and were more varicose than unconditioned phasic terminals. Following long-term tonic stimulation of the phasic axon, its terminals became more varicose, mitochondrial cross-sectional area more than doubled, and synapses and mitochondria came into closer proximity, although mean terminal cross-sectional area did not change. Thus, the conditioned phasic terminals became more similar to those of the tonic motor axon. These changes in ultrastructure correlate with, and may be causally linked to, previously reported changes in neuromuscular synaptic physiology produced by in vivo tonic stimulation of this motoneuron. We conclude that the ongoing level of impulse activity can affect the ultrastructural differentiation of synaptic terminals and synapses of the phasic motoneuron.
对相对“沉默”的阶段性小龙虾运动神经元进行体内刺激，会使其突触终末的超微结构转变为更具紧张性的表型。小龙虾爪的近端肌肉仅由2个兴奋性运动神经元支配，其中一个是阶段性的，另一个是紧张性的。对条件性阶段性、非条件性阶段性和紧张性运动终末的超微结构进行了比较。紧张性运动轴突的终末在横截面积上更大，线粒体更大，突触接触面积更大，并且比非条件性阶段性终末更具曲张性。在对阶段性轴突进行长期紧张性刺激后，其终末变得更具曲张性，线粒体横截面积增加了一倍多，突触和线粒体靠得更近，尽管平均终末横截面积没有变化。因此，条件性阶段性终末变得更类似于紧张性运动轴突的终末。这些超微结构的变化与之前报道的对该运动神经元进行体内紧张性刺激所产生的神经肌肉突触生理学变化相关，并且可能存在因果联系。我们得出结论，冲动活动的持续水平可以影响阶段性运动神经元突触终末和突触的超微结构分化。
