Subcellular innervation patterns of the calcitonin gene-related peptidergic efferent terminals in the chinchilla vestibular periphery.
We examined the ultrastructural distribution of calcitonin gene-related peptide immunoreactivity in the peripheral vestibular system of the chinchilla to study the innervation patterns of this efferent neuropeptide. Immunoelectron microscopic localization of calcitonin gene-related peptide immunoreactive terminals in the maculae and cristae revealed an extensive innervation pattern on the afferent vestibular pathway. Calcitonin gene-related peptide immuno-reactive terminals made synaptic contacts with the unmyelinated portions of the primary afferent vestibular dendrites innervating both type I and type II hair cells. Abundant synaptic contact between calcitonin gene-related peptide immunoreactive terminals and the chalices surrounding type I hair cells was observed. Direct contact between calcitonin gene-related peptide immunoreactive terminals and type II hair cells was observed. In addition, vesiculated efferent terminals without calcitonin gene-related peptide immunoreactivity were seen synapsing on the chalices of type II hair cells and on the surrounding type I hair cells. The primary afferent somata in the vestibular ganglion of Scarpa did not contain calcitonin gene-related peptide immunoreactivity. Unmyelinated calcitonin gene-related peptide immunoreactive axons passed among the primary afferent fibers in Scarpa's ganglion, and these fibers continued through the subepithelial regions of the vestibular end-organs. The calcitonin gene-related peptide immunoreactive axons ramified to produce numerous calcitonin gene-related peptide immunoreactive terminals throughout the neurosensory epithelium of the maculae and cristae. These data suggest that calcitonin gene-related peptide-mediated modulation of the afferent vestibular system is functionally important.
Ishiyama
A
A
Goodhill Ear Center, Section of Otology, 90024-1794.
Lopez
I
I
Wackym
P A
PA
D000818:Animals; D001369:Axons / Q000737:chemistry / Q000648:ultrastructure; D015740:Calcitonin Gene-Related Peptide / Q000032:analysis*; D002682:Chinchilla; D004525:Efferent Pathways / Q000737:chemistry*; D018069:Hair Cells, Vestibular / Q000737:chemistry / Q000648:ultrastructure; D008297:Male; D009411:Nerve Endings / Q000737:chemistry* / Q000648:ultrastructure; D051381:Rats; D014722:Vestibule, Labyrinth / Q000294:innervation* / Q000648:ultrastructure
D015740:Calcitonin Gene-Related Peptide