A morphological study on vestibular sensory epithelia in a strain of the waltzing guinea pig.

The crista ampullaris, the macula utriculi and the macula sacculi in the waltzing guinea pig were investigated with light microscopy, transmission and scanning electron microscopy. The degenerative changes consist of increasing degrees of apical protrusion of the type I hair cell into the endolymphatic space and of sensory hair fusion. The development of an intracellular actin filament rod in the type I hair cell is coupled to the degenerative changes of the apical part of the cell. Progressive hair cell degeneration with actin rod formation and sensory hair fusion as two important findings in the degenerative pattern is observed in type I hair cells of all sensory areas in the vestibular part of the labyrinth in the waltzing guinea pig. Scanning electron microscopy, shows a concentration of the more advanced stages of degenerative changes to the central part of the crista ampullaris and to the striolar area in the macula utriculi and in the macula sacculi. The fact that there is a concentration of sensory cell damage in the central areas of the vestibular end organs in genetically induced inner ear disease as well as in other inner ear damage supports the concept that the central areas have a different function. This paper further supports earlier suggestions that the type I and type II hair cells are genetically different cell types having different functions.