Lannoo M J, Maler L
Neuroscience Program, College of Osteopathic Medicine, Ohio University, Athens 45701.
J Comp Neurol. 1990 Apr 1;294(1):153-60. doi: 10.1002/cne.902940112.
We demonstrate that preterminal axons composing the primary afferent projection onto the four somatotopically organized electrosensory lateral line lobe (ELL) segments in weakly electric gymnotiform teleosts course in fundamentally different directions in the most commonly studied species. Afferents enter the deep fiber layer (dfl) of the ELL and course in variable, but species-specific, directions within a horizontal plane before turning dorsally to terminate within the deep neuropil layer of the ELL (dnl). Among the species considered here, apteronotids exhibit the tightest projection pattern. Afferents enter the rostral ELL from the anterior lateral line nerve ganglion (ALLNG) in a nonsomatotopic fashion. As they course horizontally, these fibers undergo a rostrocaudal somatotopic sorting along the ventrolateral border of the dfl, then turn within a horizontal plane to course medially across the ELL segments. These medially coursing horizontal fibers are sorted: they form sublaminae according to the nerve branch containing their peripheral axon. Horizontal axons then turn dorsally, form fascicles, and terminate within the dnl. Within the dorsal fascicles, axons run directly into the dnl with little deviation, and their terminal fields exhibit no appreciable spread. In sternopygids, dfl horizontal fibers course in directions orthogonal to those in apteronotids. Fibers enter the rostral ELL and course medially across segments before turning caudally within segments. Unlike apteronotids, sternopygid horizontal fibers do not sort tightly by nerve branch. As horizontal axons turn dorsally they also form tight fascicles. But rather than terminating directly and without spreading, as in apteronotids, sternopygid fibers disperse from these fascicles and become sorted horizontally a second time prior to terminating in the dnl.(ABSTRACT TRUNCATED AT 250 WORDS)
我们证明，在弱电裸背电鳗形硬骨鱼中，构成主要传入投射至四个按躯体定位组织的电感受侧线叶（ELL）节段的终末前轴突，在最常研究的物种中沿根本不同的方向走行。传入神经进入ELL的深层纤维层（dfl），并在水平平面内沿可变但物种特异性的方向走行，然后转向背侧，在ELL的深层神经毡层（dnl）内终止。在此处考虑的物种中，无鳍电鳗科表现出最紧密的投射模式。传入神经以前躯体定位的方式从前外侧线神经节（ALLNG）进入吻侧ELL。当它们水平走行时，这些纤维沿着dfl的腹外侧边界进行头尾向的躯体定位分选，然后在水平平面内转向，向内侧穿过ELL节段。这些向内侧走行的水平纤维被分选：它们根据包含其外周轴突的神经分支形成亚层。水平轴突然后转向背侧，形成束，并在dnl内终止。在背侧束内，轴突几乎没有偏差地直接进入dnl，并且它们的终末场没有明显的扩散。在颈电鳗科中，dfl水平纤维的走行方向与无鳍电鳗科的正交。纤维进入吻侧ELL并向内侧穿过节段，然后在节段内转向尾侧。与无鳍电鳗科不同，颈电鳗科的水平纤维不会按神经分支紧密分选。当水平轴突转向背侧时，它们也形成紧密的束。但是，与无鳍电鳗科不同，颈电鳗科的纤维不是直接终止且不扩散，而是从这些束中分散，并在终止于dnl之前再次进行水平分选。（摘要截短于250字）
