Passage of dextran magnetite nanoparticles through the subcupular space of the pigeon

We examined the permeability of the subcupular space for endolymph flow in the pigeon. A new technique was developed in which nanoparticles consisting of dextran magnetite were attracted by use of a magnet, instead of injecting a dye solution. The method was revealed to prevent an excess pressure application by the injection of dye solution. The Berlin blue color resulting from the dextran magnetite nanoparticles was found mainly within the subcupular space contacting with the sensory hairs. Further formation of the Berlin blue was found within the sensory cells. The result supports the idea that the fluid passes through the subcupular space.