Mihara M, Hashimoto K, Ueda K, Kumakiri M
J Invest Dermatol. 1979 Nov;73(5):325-34. doi: 10.1111/1523-1747.ep12550322.
Longitudinal serial sections of one half of the entire sinus hair of a mouse were examined by the electron microscope. Three neurites entering the outer root sheath from the perifollicular blood sinus were encountered. These were separate nerve trunks from those connected with perifollicular tactile nerve endings and exclusively innervated intrafollicular Merkel cells. Two types of specialized junctions were observed at the contact regions between Merkel cell plasma membrane and neurite plasma membrane: (i) desmosome-like structures in which small clear vesicles and/or the large cored vesicles of neurite and thicker membrane (post-synaptic?) of apposed Merkel cell were found ant (ii) synapse-like structures in which Merkel cell granules were concentrated near the plasma membrane and the membrane of the apposed neurite was usually thicker (post-synaptic?). In some of the synapse-like junctions the limiting membrane of Merkel cell granules fused with the Merkel cell plasma membrane and its content seemed to be discharged into the intercellular space. This suggested actual exocytotic secretion of Merkel cell granules. Juxtaposition of 2 types of junctions, i.e. (i) and (ii) above, was also found. This suggested the possibility that the reciprocal synapse would be present between Merkel cells and afferent neurites.
用电子显微镜检查了一只小鼠整个鼻窦毛一半的纵向连续切片。发现有三条神经突从毛囊周围血窦进入外根鞘。这些是与毛囊周围触觉神经末梢相连的神经干之外的独立神经干，专门支配毛囊内的默克尔细胞。在默克尔细胞质膜与神经突质膜的接触区域观察到两种特殊连接：（i）类似桥粒的结构，在其中发现了神经突的小透明囊泡和/或大核心囊泡以及相邻默克尔细胞较厚的膜（突触后膜？）；（ii）类似突触的结构，其中默克尔细胞颗粒集中在质膜附近，相邻神经突的膜通常较厚（突触后膜？）。在一些类似突触的连接中，默克尔细胞颗粒的界膜与默克尔细胞质膜融合，其内容物似乎被释放到细胞间隙中。这表明默克尔细胞颗粒存在实际的胞吐分泌。还发现了上述两种连接类型，即（i）和（ii）的并置。这提示了默克尔细胞与传入神经突之间可能存在相互突触的可能性。
