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Cyclic GMP inhibits and shifts the activation curve of the delayed-rectifier (IK1) of type I mammalian vestibular hair cells

1997; Lippincott Williams & Wilkins; Volume: 8; Issue: 12 Linguagem: Inglês

10.1097/00001756-199708180-00010

1473-558X

Oliver Behrend, C. Schwark, Takanobu Kunihiro, Michael Strupp,

Ion Channels and Receptors

NITRIC oxide (NO) plays a role in the modulation of the predominant potassium current of type I vestibular hair cells, a low-voltage activated current called IK1. Since many effects of NO are mediated via cGMP, patch-clamp recordings were made to evaluate the effects of cGMP on IK1. In whole-cell recordings 1 mM cGMP shifted Vhalf of IK1 by 15.0 ± 2.4 mV (n = 6) to more positive. In cell-attached 'multichannel' recordings 1 mM 8-bromo-cGMP caused a reversible shift of Vhalf by 13.8 ± 2.6 mV (n = 12) and in single channel recordings in the cell-attached configuration the open probability was reduced at −60 mV from 0.39 ± 0.14 to 0.08 ± 0.01. cGMP had no effect on excised inside-out patches, indicating that an intact cytosolic milieu with functioning phosphorylation cascades is necessary. cGMP seems to be an important second messenger which reduces the potassium conductance of vestibular hair cells.