A fluorescence and electron microscopic study of the adrenergic innervation in the vestibular ganglion and sensory areas.

The adrenergic innervation in the vestibular ganglion and sensory areas in rabbit and cat was studied with fluorescence and electron microscopic techniques. All adrenergic nerve fibres consisted of postganglionic axons from the ipsilateral superior cervical ganglion. In rabbit, postganglionic nerve fibres passed via the carotic plexus. Probably because of the anatomical difference, the feline internal carotic artery being rudimentary, all sympathetic nerve fibres to the inner ear in cat passed via the tympanic plexus. In the vestibular ganglion there was a uniform distribution of adrenergic nerve fibres and there was no difference in distribution patterns between rabbit and cat. There was a continuous blood vessel innervation and an innervation independent of blood vessles. The adrenergic innervation extended to the sensory areas but did not seem to penetrate the basement membrane and no adrenergic nerve terminals were found in direct contact with sensory or secretory cells.