| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Resting potential (r.p.) and muscarinic response mechanisms were studied in Xenopus laevis oocytes using the voltage-clamp technique. Insertion of micro-electrodes into the oocyte produced a 'shunt' membrane conductance which partially sealed after a few minutes. The oocyte resting potential (measured with a single intracellular electrode) ranged from -40 to -60 mV. Ouabain and low K+ solution depolarized both follicles and denuded oocytes. The electrogenic Na+-K+ pump was more active in the latter. In the presence of ouabain, the r.p. agreed with the constant field theory. alpha (PNa+/PK+) was 0.12 in follicles and 0.24 in denuded oocytes. beta (PCl-/PK+) was 0.4 in both. At [Na+]o lower than 70 mM, the r.p. deviated considerably from the constant field predictions. The relatively large value of alpha indicated the major role of Na+ in oocyte r.p. determination. The oocyte muscarinic response was separated into four distinct components: the fast depolarizing Cl- current, 'D1'; the slow depolarizing Cl- current, 'D2'; the slow hyperpolarizing K+ current, 'H'; and the large membrane Cl- current fluctuation, 'F'. The H response reversal potential showed a Nernst relationship to [K+] and was selectively blocked by intracellular injection of tetraethylammonium (TEA). The D1 and D2 reversal potential showed a Nernst relationship to [Cl-]. In Ca2+-deficient, EGTA-containing medium, D2 and F were abolished and D1 and H were reduced. Verapamil inhibited all responses. Increasing [Ca2+]o caused a significant increase in D1, D2 and F response amplitudes. Intracellular injection of 0.6-10 pmol guanosine 3',5'-cyclic monophosphate, induced a large outward K+ current, similar to the muscarinic H response.
This article has been cited by other articles:
|
|
 |
|
  Y. Ben-Chaim, O. Tour, N. Dascal, I. Parnas, and H. Parnas The M2 Muscarinic G-protein-coupled Receptor Is Voltage-sensitive J. Biol. Chem., June 13, 2003; 278(25): 22482 - 22491. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Chorna-Ornan, T. Joel-Almagor, H. C. Ben-Ami, S. Frechter, B. Gillo, Z. Selinger, D. L. Gill, and B. Minke A Common Mechanism Underlies Vertebrate Calcium Signaling and Drosophila Phototransduction J. Neurosci., April 15, 2001; 21(8): 2622 - 2629. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Pushkin, N. Abuladze, I. Lee, D. Newman, J. Hwang, and I. Kurtz Cloning, Tissue Distribution, Genomic Organization, and Functional Characterization of NBC3, a New Member of the Sodium Bicarbonate Cotransporter Family J. Biol. Chem., June 4, 1999; 274(23): 16569 - 16575. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. Zwart and H. P. M. Vijverberg Potentiation and Inhibition of Neuronal Nicotinic Receptors by Atropine: Competitive and Noncompetitive Effects Mol. Pharmacol., November 1, 1997; 52(5): 886 - 895. [Abstract] [Full Text]
|
|
|
|
|
|
J. T. Fleming, M. D. Squire, T. M. Barnes, C. Tornoe, K. Matsuda, J. Ahnn, A. Fire, J. E. Sulston, E. A. Barnard, D. B. Sattelle, et al. Caenorhabditis elegans Levamisole Resistance Genes lev-1, unc-29, and unc-38 Encode Functional Nicotinic Acetylcholine Receptor Subunits J. Neurosci., August 1, 1997; 17(15): 5843 - 5857. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Matus-Leibovitch, D. R. Nussenzveig, M. C. Gershengorn, and Y. Oron Truncation of the Thyrotropin-releasing Hormone Receptor Carboxyl Tail Causes Constitutive Activity and Leads to Impaired Responsiveness in Xenopus Oocytes and AtT20 Cells J. Biol. Chem., January 20, 1995; 270(3): 1041 - 1047. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. J. Hill and E. G. Peralta Inhibition of a Gi-activated Potassium Channel (GIRK1/4) by the Gq-coupled m1 Muscarinic Acetylcholine Receptor J. Biol. Chem., February 16, 2001; 276(8): 5505 - 5510. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
