大鼠中脑水管周围灰质腹外侧部神经毡的超微结构研究

ULTRASTRUCTURAL STUDY OF THE NEUROPIL IN VENTROLATERAL PAG IN THE RAT

应用电镜技术，观察了大鼠中脑水管周围灰质（ＰＡＧ）腹外侧部内侧区和外侧区神经毡的超微结构。结果显示，外侧区神经毡有髓纤维多为直径大于１２μｍ的粗纤维，髓鞘厚度不等；树突直径多在１２～１５μｍ之间；突触型式以轴—树突触占优势，易见多个轴突终扣与同一树突形成突触或突触复合体，亦观察到轴—体突触、轴—轴突触和树—树突触。内侧区神经毡内有髓纤维分布稀疏，多为０６～１４μｍ的薄髓纤维；树突数量多，其直径多在１μｍ以下；突触形式有轴—树突触、轴—树突棘突触和轴—体突触。上述结果揭示了ＰＡＧ腹外侧部的内侧区和外侧区神经毡存在构筑差异。

The ultrastructure of neuropil in medial and lateral regions of the ventrolateral midbrain periaqueductal gray (PAG) of the rat were investigated by electron microscope. In the lateral region,the myelinated axons are numerous and more than 1 2μm in dianeter, surrounded by a thick or thin myelin sheath. The majority of dendrites were 1 2～1 5μm in diameter. Axodendritic synapse was the dominant form of the synaptic interactions in lateral region,both a central dendrite surrounded by several presynaptic axonal boutons and a central axonal bouton making synatic contacts with two dendrites were found. Other types of the synaptic interactions in the lateral region were axosomatic,axonic and dendrodendritic synapses. In the medial region,myelinated axons were sparse in the neuropil. They were relatively small in diameter (0 6～1 4μm) and surrounded by a thin myelin sheath. The dendrites were numerous and always less than lum in diameter. The forms of synaptic interaction in the medial region were axodendritic and axosomatic.These results revealed the different morphology and synaptic organization of neuropil between medial and lateral regions of the ventrolateral PAG.