Experimental Studies on the Nerve–Sensory Cell Relationship during Degeneration and Regeneration in Ampullar Nerves of the Frog Labyrinth

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Abstract
The degeneration and regeneration of afferent and efferent nerves to the crista ampullaris in the frog were studied after transsection of the ampullar nerves. In some experiments one or both rostral ampullar nerves were simply divided and left in place. In other experiments the ampullar nerves to the horizontal and to the anterior vertical crista were divided and the branch to the former was brought into contact with the distal stump of the anterior vertical ampullar nerve. Sensory cells in the labyrinth survived total denervation for 1-2 weeks without regular signs of ultrastructural damage. The afferent synaptic structures in these cells were often preserved in the denervated stage. The afferent nerve fibres degenerated earlier than the efferent ones. Both type of fibres reinnervated the vestibular epithelium after division of the ampullar nerve. The fibres from a horizontal ampullar nerve could reinnervate a denervated anterior vertical crista, resulting in misdirected reflexes. About 40 days after division both function and morphological organization had been restored to normal.