effect of kanamycin on potassium currents in isolated supporting cells from the guinea-pig cochlea *
The auditory sensory organ of mammals, the organ of Corti, is located on the basilar membrane. This organ consists of two types of sensory hair cells, outer and inner hair cells (ＯＨＣｓ and ＩＨＣｓ) , and a surrounding network of various supporting cells, the largest part of which is made of Deiters' cells (ＤＣｓ) and Hensen's cells (ＨＥｓ). The aim of the present study was to determine whether voltage-dependent currents exist in the supporting cells which are associated with the hair cells, and whether these currents are affected by kanamycin (ＫＭ), an ototoxic drug to ＯＨＣｓ. In the present experiment, two types of supporting cells, ＤＣｓ and ＨＥｓ, were freshly isolated from the guinea-pig cochlea, and the current-voltage relations of these cells were examined by conventional whole cell recording techniques. It was found that the whole cell currents of both ＤＣｓ and ＨＥｓ were voltage-dependent outward Ｋ currents, because these currents were suppressed almost completely by the extracellular ＣＳ ions, and 80％ were suppressed by 10 ｍＭ ＴＥＡ. When 10-4 Ｍ ＫＭ was added to the extracellular solution, the voltage-dependent outward Ｋ currents in the ＤＣｓ were increased more than those in a normal extracellular solution, but these increased currents were not dependent on the Ｃａ ions in the extracellular solution. On the other hand , the currents in ＨＥｓ were not changed by 10-4 Ｍ ＫＭ in extracellular solution. From these results, it was suggested that ＫＭ has inhibitory effects on the voltage-dependent Ｃａ channel and that a mechanosensor channel in ＯＨＣ, accelated the voltage-dependent outward Ｋ currents in ＤＣｓ. (Accepted on October 28, 1997) Kawasaki Igakkaishi 23(3) : 155-164, 1997
