Gap junctional connections between hair cells, supporting cells and nerves in a vestibular organ.

The pattern of gap-junctional connections between cells in the vestibular neuroepithelium of the posterior semicircular duct of the alligator lizard are described based upon the study of freeze fracture replicas and ultrathin sections with a transmission electron microscope. Both type I and type II hair cells are coupled to adjacent supporting cells by a series of small macular gap junctions located in a ring around the hair cell at the level of the apical circumferential belt of actin filaments. Adjacent supporting cells are extensively interconnected by gap junctions. A few cases of gap junctions between afferent dendrites and supporting cells, and between afferent dendrites and calyceal nerve endings were seen. These morphological observations together with data from other studies in the literature suggest a possible role for supporting cells in altering the micromechanical properties of the hair cell receptor organs during stimulation.