HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Shigemoto, T Articles by Ohmori, H Search for Related Content PubMed PubMed Citation Articles by Shigemoto, T Articles by Ohmori, H

National Institute for Physiological Science, Myodaiji, Okazaki, Japan.

1. Electrical responses to extracellularly applied acetylcholine (ACh) and to intracellularly introduced substances were studied in isolated short and tall hair cells from the chick cochlear organ by a whole-cell voltage clamp technique using a patch electrode. These cells were isolated without using proteolytic enzymes. 2. Short hair cells generated a transient outward current at -50 mV in normal saline in response to puff-applied 100 microM-ACh, when the patch electrode was filled with a 160 mM-K+ and 100 microM-EGTA-based intracellular medium. The amplitude was 317.1 +/- 97.1 pA (n = 32). When ACh was applied ionophoretically, the outward current was generated with a delay of about 10 ms. 3. The amplitude of ACh-induced current was dose dependent with a KD of 19 microM and a Hill coefficient of 1.6 when measured at -50 mV. 4. The ACh (100 microM)-induced current was suppressed by 1 microM-atropine. ACh-induced current was generated in a Ca(2+)-free extracellular medium; however, the second ACh puff in the Ca(2+)-free medium generated a much reduced response. ACh-induced current was suppressed reversibly by 100 microM-quinine. 5. Intracellular injections of guanosine-5'-O-(3-thiotriphosphate) (GTP gamma S), inositol 1,4,5-trisphosphate (IP3) or Ca2+ (1 microM) via the patch pipette activated outward currents at -50 mV. 6. When the internal medium with strong Ca(2+)-buffering capacity (5 mM-EGTA) was used, the ACh-induced current was reduced to 39.3 +/- 6.8 pA (n = 4) at -50 mV (12.3% of the response in the low-EGTA medium). 7. The reversal potential of the ACh-induced current was -85.7 +/- 4.2 mV (n = 3) in normal saline containing 5 mM-K+. The reversal potential was dependent on the extracellular K+ concentration ([K+]o) and was shifted 57 mV by a 10-fold increase in [K+]o at room temperature (20-25 degrees C). 8. These results (points 4-7) indicate that ACh induces a K+ conductance by releasing Ca2+ intracellularly, probably by activating the pathway of muscarine receptor, G-protein and IP3. 9. Channel activities were recorded using cell-attached patch electrodes. Channel activities were rarely observed when ACh was applied to the extra-patch membrane, while robust channel activities were observed when ACh was included in the patch pipette medium. It is therefore suggested that Ca(2+)-activated K+ channels exist in the membrane in close vicinity to muscarinic receptor molecules and intracellular Ca2+ release sites.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				D. Zenisek, V. Davila, L. Wan, and W. Almers Imaging Calcium Entry Sites and Ribbon Structures in Two Presynaptic Cells J. Neurosci., April 1, 2003; 23(7): 2538 - 2548. [Abstract] [Full Text] [PDF]

				D. Z. Z. He and P. Dallos Development of Acetylcholine-Induced Responses in Neonatal Gerbil Outer Hair Cells J Neurophysiol, March 1, 1999; 81(3): 1162 - 1170. [Abstract] [Full Text] [PDF]

				P. Dallos, D. Z. Z. He, X. Lin, I. Sziklai, S. Mehta, and B. N. Evans Acetylcholine, Outer Hair Cell Electromotility, and the Cochlear Amplifier J. Neurosci., March 15, 1997; 17(6): 2212 - 2226. [Abstract] [Full Text] [PDF]