GAP JUNCTIONAL CONNECTIONS BETWEEN HAIR-CELLS, SUPPORTING CELLS AND NERVES IN A VESTIBULAR ORGAN

The pattern of gap-junctional connections between cells in the vestibu lar neuroepithelium of the posterior semicircular duct of the alligato r lizard are described based upon the study of freeze fracture replica s and ultrathin sections with a transmission electron microscope. Both type I and type II hair cells are coupled to adjacent supporting cell s 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 b y gap junctions. A few cases of gap junctions between afferent dendrit es and supporting cells, and between afferent dendrites and calyceal n erve 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 ha ir cell receptor organs during stimulation.