Canalicular reticulum in vestibular hair cells

A membrane limited system referred to as canalicular reticulum (CR) has bee n demonstrated in the apical cytosol of the cochlea's inner and outer hair cells. Similarities between cochlear and vestibular hair cells prompted inv estigation of the presence of CR in hair cells of the gerbil vestibular lab yrinth. A method of fixation with glutaraldehyde followed by an osmium-ferr ocyanide mixture demonstrated abundant CR in the apex of both type I and ty pe II hair cells. The CR was closely associated with numerous Golgi zones i n the apex of the vestibular hair cells, indicating its genesis from Golgi cisternae. Also preserved in upper cytosol were discrete complexes of mitoc hondria with granular reticulum. These complexes offered a possible site fo r generating the membrane in Golgi zones and CR. Single and parallel cister nae of granular reticulum were observed in the basal half of the hair cells together with numerous synaptic-like vesicles. These cisternae with their terminal blebbing and accompanying canaliculi were interpreted as novel str uctures mediating synaptic vesicle genesis in vestibular hair cells in a ma nner comparable to that postulated for cochlear inner hair cells. (C) 2000 Elsevier Science B.V. All rights reserved.