Fine structure of noradrenaline containing nerve fibers in the median eminence of female rat demonstrated by in situ fixation of potassium permanganate.

Fine structure of noradrenaline (NA) terminals in the internal layer of the median eminence (ME) was elucidated by in situ fixation of potassium permanganate. The NA terminals in ME contained relatively large cored vesicles (about 1000 A) together with a large number of small core vesicle (400-600 A). The most dominant feature that NA terminals show is the closed contact with ependymal cells and their processes. In the bulging abutting on the contact membrane, some of core vesicles fused or touched the membrane appearing to release the content into intercellular space or take up NA from the space. This finding shows that the NA terminals abutting on the ependymal cells and their processes have a close contact with them and give an important influence on regulation of ependymal function. Our present study further revealed that the NA terminals also had a close contact not only with the axon terminals in which ordinary spherical non-cored vesicles were exclusively present but also with the axonal fibers of neurosecretary system. These findings would infer complicated function of NA in ME.