Changes made to field aliases in ArcMap aren't reflected in ArcCatalog on the geodatabase feature class properties dialog box.
Field aliases in ArcMap and ArcCatalog are different. The link between them only goes in one direction, and is only dynamic to a point.
When you add a feature class to ArcMap, a layer is created in the map. For geodatabase data, the field aliases for this layer come from the feature class field aliases as defined in ArcCatalog; however, at this point the link between the two sets of aliases is broken. This means:
· Any changes made to field aliases in ArcMap will never affect the feature class aliases.
· After adding data, if you save your layer as part of an .mxd, or as a .lyr file, subsequent changes to the feature class field aliases in ArcCatalog will not propagate to the layer field aliases in the .mxd or .lyr. This is because layer field aliases are stored separately from feature class field aliases, and the link between them is only dynamic to the point of adding data to ArcMap.