Fischer W, Fischer H, Uerlings I, David H
Z Mikrosk Anat Forsch. 1975;89(2):340-66.
The slowly adapting abdominal stretch receptors of Orconectes limosus (RAF) have been investigated morphologically; 1. Despite their variety of size and shape all slowly adapting receptor neurons show common characteristic features which in addition distinguish them clearly from the fast adapting receptor neuron type SN2. The slightly globular cells have always several dendrites (often 4-6). They originate apical or lateral to the neuron, are oriented mainly longitudinal to the muscle fibres and are brodly ramified. The fine dendrites form a 3-dimensional fibrilar network. 2. The structure and distribution of the connective tissue in the "intertendon" of the muscle receptor organ correspond to the dendrite ramification; In this area, some muscle fibres end direktly at tendon-like connective tissue structures, but a number of different fibres run uninerruptedly through the whole muscular fascicle. 3. The perikaryon of every sensory neuron shows 2 "cytoplasm types" which are clearly distinguishable one against the other. A characteristic feature of the granular-lamellar neuroplasm that closely surrounds the nucleus are many flat vesicles of the granular endoplasmatic reticulum, accumulations of free ribosomes, numerous mitochondria and Golgi fields. The fibril-rich neuroplasm on the contrary contains only few mitochondria, but very many neurofilaments, here and there also neurotubuli. It projects directly into the dendrites and neuritek. Cell bodies, axon and dendrites are surrounded alternatingly by sheath cells and connective tissue of collagenous nature. The innermost layer of the coat cells borders directly on the neuron membrane. Finer dendrites are enclosed by nothing more but a thin layer of sheath cell plasm and intercellular substance. The dendrite terminals are either stored directly in connective tissue ground substance or border immediately on the sarcoplasm. 5. The axo-dendritic or axo-somatic synapses, respectively, contain numerous ellipsoidal (250-350 X 400-500 A), but also many spherical, vesicles. Some vesicles have a slightly larger diameter (700-900 A) and contain an electron-dense core. The synaptic gap measures 150 to 200 A. The neuromuscular (supposedly excitatory) synapses are filled much lighter with vesicles as compared with those just mentioned, which show a relatively unique form and size (nearly all spherical, phi 400-500 A). There are less vesicles with an electron-dense centre. On the average, the synaptic gap is broader (200-250 A) and the contact zone is larger. Apart from these, terminals could be observed in the dendritic ramification area, too, resembling the axo-dendritic and axo-somatic ones, respectively. 6. Finer dendrite branches contain vesicles differing slightly from those mentioned above as far as shape and size are concerned. Their diameters vary between 500 and 1 000 A. "Dense bodies" could be observed sporadically in these vesicles.
对拟螯虾（Orconectes limosus，RAF）的慢适应性腹部牵张感受器进行了形态学研究；1. 尽管慢适应性感受器神经元大小和形状各异，但均具有共同的特征，这使其与快适应性感受器神经元类型SN2明显区分开来。略呈球形的细胞通常有多个树突（通常为4 - 6个）。它们起源于神经元的顶端或侧面，主要沿肌肉纤维纵向排列，并广泛分支。细小的树突形成三维纤维网络。2. 肌肉感受器器官“腱间”结缔组织的结构和分布与树突分支相对应；在该区域，一些肌肉纤维直接终止于腱样结缔组织结构，但许多不同的纤维不间断地贯穿整个肌束。3. 每个感觉神经元的胞体显示出两种“细胞质类型”，二者明显可区分。紧密围绕细胞核的颗粒状 - 板层状神经浆的一个特征是有许多颗粒内质网的扁平小泡、游离核糖体聚集、大量线粒体和高尔基体区域。相反，富含纤维的神经浆仅含有少量线粒体，但有许多神经丝，各处还有神经微管。它直接伸入树突和神经突。细胞体、轴突和树突交替被鞘细胞和胶原性质的结缔组织包围。被膜细胞的最内层直接与神经元膜相邻。较细的树突仅被一层薄的鞘细胞质和细胞间质包围。树突末端要么直接储存在结缔组织基质中，要么紧邻肌浆。5. 轴 - 树突触或轴 - 体突触分别含有许多椭圆形（250 - 350×400 - 500埃）的小泡，但也有许多球形小泡。一些小泡直径稍大（700 - 900埃），并含有电子致密核心。突触间隙为150至200埃。与上述突触相比，神经肌肉（可能是兴奋性的）突触小泡填充较轻，这些突触显示出相对独特的形态和大小（几乎全是球形，直径400 - 500埃）。电子致密中心的小泡较少。平均而言，突触间隙更宽（200 - 250埃），接触区更大。除此之外，在树突分支区域也可观察到终端，分别类似于轴 - 树突触和轴 - 体突触。6. 较细的树突分支含有在形状和大小上与上述小泡略有不同的小泡。它们的直径在500至1000埃之间变化。在这些小泡中偶尔可观察到“致密体”。
