Tetraethylammonium effects on cochlear potentials in the guinea pig.
Voltage-dependent K+ channels in the basolateral membrane of hair cells in guinea-pig cochlea might contribute to the non-linear current-voltage relationships in these hair cells and, thereby, to generation of the extracellular summating potential (SP). To evaluate the role of K+ channels in the generation of the SP the perilymphatic perfusion technique was used to introduce the K(+)-channel blocker tetraethylammonium (TEA) into the cochlea. Sound-evoked cochlear potentials were measured subsequently. Without blocking nerve activity TEA induced reversible shifts of the SP in the negative direction, irrespective of whether we recorded from scala vestibuli or scala tympani. Shifts in the negative direction were probably due to TEA acting directly on the afferent fibres, since removal of nerve activity by the potent Na(+)-channel blocker tetrodotoxin (TTX) prevented TEA from shifting the SP in the negative direction. Once nerve activity had been removed by TTX, administration of TEA caused a small decrease in the magnitude of the SP, both in scala vestibuli and in scala tympani, irrespective of its polarity. The decrease was significant for the highest test frequencies only (8-12 kHz), and completely reversible. The rapidly activated K+ channel in the inner hair cell (IHC) is probably blocked by TEA and this blocking might be responsible for the small decrease in magnitude of the SP. The asymmetric contribution from this K+ channel to the IHC's current-voltage relationship seems to be only partly responsible for the generation of the SP, since blocking of this K+ channel with TEA caused relatively small decreases in the amplitude of the SP. TEA did not affect the endocochlear potential.
van Emst
M G
MG
Department of Otorhinolaryngology, Utrecht University, The Netherlands.
Klis
S F
SF
Smoorenburg
G F
GF
D000161:Acoustic Stimulation; D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001309:Auditory Threshold / Q000187:drug effects; D003051:Cochlea / Q000187:drug effects* / Q000502:physiology; D005072:Evoked Potentials, Auditory / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects / Q000502:physiology; D009412:Nerve Fibers / Q000187:drug effects; D009475:Neurons, Afferent / Q000187:drug effects; D015221:Potassium Channels / Q000187:drug effects* / Q000502:physiology; D012533:Scala Tympani / Q000187:drug effects / Q000502:physiology; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology*; D013779:Tetrodotoxin / Q000494:pharmacology; D014722:Vestibule, Labyrinth / Q000187:drug effects / Q000502:physiology
D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D013779:Tetrodotoxin; D019789:Tetraethylammonium