title: Fine structure of the palisade zone of the rat median eminence as revealed by freeze-fracturing.
abstract: Nerve terminals in the palisade zone of the rat median eminence were investigated with freeze-fracture electron microscopy. Fracture face P of the specific terminals showed two populations of intramembranous particles (IMP): a large and a small variety. The large IMP-s often formed small irregular clusters. In nerve terminals the total number of both populations of IMP-s was considerably less than that found on P membrane faces of ependymal feet. On fracture face E of the nerve terminals, the number of IMP-s was about a quarter of that seen on fracture face P. On both fracture faces of most terminals a few small round impressions (or elevations respectively) were found which may be interpreted as broken necks of either exo- or endocytotic vesicles. Neither gap nor tight junctions occurred at lateral membranes of the specific axon terminals. Similarly, no membrane specializations were observed with freeze-fracturing on membrane areas adjacent to the basement membrane. The findings are discussed in relation to a possible exocytosis mechanism of the hypothalamic releasing and inhibiting hormones.
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure; D002462:Cell Membrane / Q000648:ultrastructure; D003094:Collagen; D003238:Connective Tissue / Q000648:ultrastructure; D005260:Female; D005614:Freeze Fracturing; D007030:Hypothalamo-Hypophyseal System / Q000648:ultrastructure*; D007365:Intercellular Junctions / Q000648:ultrastructure; D008297:Male; D008473:Median Eminence / Q000648:ultrastructure*; D009411:Nerve Endings / Q000648:ultrastructure; D051381:Rats
chemical_list: D003094:Collagen