The fine structure of the cochlear plexus.

Ultrathin sections and freeze-fracture replicas of the guinea pig cochlear plexus were studied under the electron microscope. Generally, the capillaries possess a continuous endothelial cell layer. The endothelial cells are connected by tight junctions. Occasionally, fenestrated capillaries can be found. Nonmyelinated nerves are intimately related to smooth muscle cells of arterioles as well as pericytes and endothelial cells of capillaries. The axonal varicosities contain clear synaptic-type vesicles. The cochlear plexus cells are connected by desmosomes, gap junctions, and tight junctions. The latter are thought to be part of the blood-perilymph-barrier in this region. There is evidence that the cochlear plexus derives from the meninges.