大鼠下丘脑弓状核突触的衰老性变化

用透射电镜结合体视学方法，对３月龄、１０月龄和３０～３４月龄大鼠弓状核突触进行了定性和定量研究。结果显示：老龄组大鼠神经毯呈萎缩变性相，大树突内脂褐素增多，小到中等大小的树突出现空泡变性、多泡体和膜被多层体等，棘萎缩减少；轴突终末内突触囊泡减少而大颗粒囊泡积聚，部分突触前、后膜变薄、缩短或间断，突触小球少见；轴－体、轴－树和轴－棘突触数减少，突触密度、突触连接带面密度和突触膜总长度降低，ＧｒａｙⅠ型和即Ⅱ型突触间隙增宽。上述结果表明，老年弓状核突触在数量、形态和结构上发生了衰老性改变，这是导致下丘脑神经内分泌衰老障碍的主要原因之一。

STUDY ON AGING CHANGES OF SYNAPTIC ARCHITECTURE IN THE HYPOTHALAMIC ARCUATE NUCLEUS OF RAT

The age-related changes of synapses in arcuate nucleus (ARCN) were studied quantitatively and qualitatively by electronmicroscope combined with stereological method at young (3 months ), middle-aged (10 months)and aged (30 ～ 34months) male SPrague-Dawley rats. In the ARCN of old animals, large-sized dendrites contained increasing number of lipofuscin, small and middle-sized dendrites were degenerating, which included vacuolation and contained inclusion bodies withirregular shape.Increasing numbers of large spherical vesicles(100 to 300 nm in diameter) or large granular vesicles coexisting with small spherical vesicles(40 to 60 nm) were detected in the axon terminals. Pre- and postsynaptic membrane werethin, short and discontinuous.The mean numbers of axodendritic, axosomatic and axodendritic spine synapses(475 μm2)were reduced,showed a mean decrease of about 50% when data was compared to young and middle-aged group.The totalsurface area of the synaptic contact zones per unit volume (Sv), total length of synaptic membrane per unit area (LA)anddensities of synapse werre found to be decreased. We have also found significant decrease in the numbers of synaptic terminalvesicles. HOwever, the width of synaptic cleft of Gray type Ⅱ and Ⅲ synapses were increased. The difference between aged and young, aged and middle-aged rats were significant for all parameter (P<0. 05). Whereas the average area, perimeter ofpre-and postsynaptic terminals did not differ significantly in aged and middle-aged group. Because the ARCN is considered tobe one of the principal neural components which regulate secretory functions of the anterior pituitary lobe loss in the numberof synapses and some degenerating changes in its neuropil during the process of aging may apparently impair its integrativecontrol mechanisms. It is plausible to suggest that aging changes in the ARCN seem to correlate with the aging of the neuroendocrine system.