Cytoarchitecture, fiber connections, and ultrastructure of nucleus isthmi in a teleost (Navodon modestus) with a special reference to degenerating isthmic afferents from optic tectum and nucleus pretectalis.

摘要: Cytoarchitecture and fiber connections of the nucleus isthmi in a teleost (Navodon modestus) were studied by means Nissl, Bodian, toluidine blue, Golgi, Fink-Heimer methods. Synaptic terminals classified ultrastructural characteristics, their origins determined electron microscopic degeneration experiments. The is composed an outer cellular area or shell inner noncellular core. The covers anterior, dorsal, ventral aspects cell bodies are oval (15 × 20 μm) with anteroposterior long axis, have many somatic spines. Spines also seen on initial segment axon. Primary dendrites extend postermedially branch out core contains thin thick myelinated fibers, which originate optic tectun pretectalis, respectively. At least two types axons terminal distinguished isthmi: S type, containing spherical vesciles, F flattened vesicles. derived from fibers only where they form asymmetric synapses dendrites. Frequently portion membrane near usual synaptic cleft close apposition adjacent small dendrite spine. terminals, make symmetric contacts both degenerate after ipsilateral ablation tectum, whereas destruction pretectalis.