Fig. 6
The resting MET current drives the maintenance of mature IHC K+ currents in cochlear cultures. a Potassium outward currents recorded from a P21 IHC of an acutely dissected gerbil cochlea. Recordings were performed using a perilymph-like solution (1.3 mM extracellular Ca2+; 5.8 mM K+). Currents were elicited using 10 mV depolarizing voltage steps from −84 mV. Note the fast activating IK,f characteristic of adult IHCs (arrow). b, c Currents recorded from IHCs maintained in cochlear culture for 1 day (b) or 6 days (c). The culture medium bathing the cochlea (see Methods) contained 1.3 mM Ca2+ and 4.2 mM K+. d, e Currents recorded from IHCs maintained in culture for 2 day (d) or 7 days (e). Culture medium contained 1.3 mM Ca2+ and 40 mM K+. f Size of IK,f recorded from IHCs of acutely isolated gerbil cochleae (gray circle, n = 6, P21-P28, 3 gerbils) or maintained in culture. Culture conditions were: (1) normal medium (black circles, number of IHCs from left to right: 7,3,4,10,2,6,7; from 9 cochlear cultures; gerbil age at the day of culturing: P18-P24); 2) medium supplemented to 40 mM K+ (blue circles, number of IHCs: 6,6,5,7, from 4 cochlear cultures, P18-P24). g, h Currents recorded from IHCs maintained in culture for 1 day (g) or 6 days (h) with a medium containing 40 µM Ca2+. i, j, l Currents from IHCs maintained in cochlear culture for 1 day (i), 4 days (j) or 8 days (l) with a medium containing 40 µM Ca2+ and 50 μM of the MET channel blocker d-tubocurarine. The inward rectifier K+ current (IK1) l was obtained using 10 mV hyperpolarizing voltage steps from −64 mV. k Size of IK,f recorded from IHCs of acutely dissected cochleae (gray circle: same as in panel f), maintained in culture with a normal medium (black circles: as in panel f), a medium containing 40 µM Ca2+ (red circles: number of IHCs: 5,10,9,5,3,5,8, from 9 cochlear cultures, P18-P24) and a medium containing 40 µM Ca2+ and 50 μM d-tubocurarine (orange circles: 4,6,6,4, from 4 cochlear cultures, P18-P24). Average data is shown as mean ± SEM
