Proceedings of the Physiological Society, 12‐14 September 1985, Cambridge Meeting: Communications

Abstract

University Walk, Bristol BS8 1TD Outer hair cells (OHC) are implicated in frequency-selective processes in the mammalian cochlea. Although resting potentials of -70 to -85 mV are found in vivo (Cody & Russell, 1985), a study of OHC properties in vitro reported much lower values (Brownell, Bader, Bertrand & De Ribaupierre, 1985). To characterize OHC membrane permeability we have measured whole cell currents from OHC dissociated from the apical two turns of the organ of Corti. When the pipette contained 140 mM-KCl and 0-25 /LM-Ca (EGTA), the cell input conductance was between 20 and 50 nS. When Na replaced K, the cell input conductance decreased to 2-9 + 0-88 nS (S.D., n = 6). Low input conductances were also obtained with Cs-EGTA (4-8 nS) in the pipette.Single channel currents were recorded from cell-attached and inside-out membrane patches. Three distinct channel types were observed ( The results suggest that the OHC membrane is highly selective for K, with only a small non-selective component. When a cat is rotated about an off-earth-vertical axis (OEVA) a continuous nystagmus is generated (Correia & Money, 1970). During OEVA rotation there are two forces simultaneously being applied to the cat: angular acceleration about the axis of rotation and a gravity vector that swings, around the animal's head. The primary drive for the continuous nystagmus is presumed to come from the otoliths sensitive to the rotating gravity vector, but the nature of the nystagmus' generation is unclear since an appropriate signal does not appear in the vestibular nerve (Goldberg & Fernandez, 1982). To reveal the role of the canals in the generation of this nystagmus I have temporarily reversed the relationship between the signals from the canals and the otoliths in three awake, unanaesthetized cats with procedures that evoked no signs of discomfort or distress.Cats were held on a table that could rotate about an axis perpendicular to the plane of the horizontal canals. Eye movements were monitored by a scleral search coil technique. The whole table could be tilted so that rotation was around an OEVA although the relationship of the animal to the axis of rotation was unchanged.