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Patch clamp measurements on Xenopus laevis oocytes: currents through endogenous channels and implanted acetylcholine receptor and sodium channels. 1986

C Methfessel, and V Witzemann, and T Takahashi, and M Mishina, and S Numa, and B Sakmann

Functional acetylcholine receptor (AChR) and sodium channels were expressed in the membrane of Xenopus laevis oocytes following injection with poly(A)+-mRNA extracted from denervated rat leg muscle. Whole-cell currents, activated by acetylcholine or by depolarizing voltage steps had properties comparable to those observed in rat muscle. Oocytes injected with specific mRNA, transcribed from cDNA templates and coding for the AChR of Torpedo electric organ, expressed functional AChR channels at a much higher density. Single-channel currents were recorded from the oocyte plasma membrane following removal of the follicle cell layer and the vitelline membrane from the oocyte. The follicle cell layer was removed enzymatically with collagenase. The vitelline membrane was removed either mechanically after briefly exposing the oocyte to a hypertonic solution, or by enzyme treatment with pronase. Stretch activated (s.a.) currents were observed in most recordings from cell-attached patches obtained with standard patch pipettes. S.a.-currents were evoked by negative or positive pressure (greater than or equal to 5 mbar) applied to the inside of the pipette, and were observed in both normal and mRNA injected oocytes indicating that they are endogenous to the oocyte membrane. The s.a.-channels are cation selective and their conductance is 28 pS in normal frog Ringer's solution (20 +/- 1 degree C). Their gating is voltage dependent, and their open probability increases toward more positive membrane potentials. The density of s.a.-channels is estimated to be 0.5-2 channels per micron 2 of oocyte plasma membrane. In cell-attached patches s.a.-currents are observed much less frequently when current measurement is restricted to smaller patches of 3-5 micron 2 area using thick-walled pipettes with narrow tips. In outside-out patches s.a.-currents occur much less frequently than in cell-attached or inside-out patches. AChR-channel and sodium channel currents were observed only in a minority of patches from oocytes injected with poly(A)+-mRNA from rat muscle. AChR-channel currents were seen in all patches of oocytes injected with specific mRNA coding for Torpedo AChR. In normal frog Ringer's solution (20 +/- 2 degrees C) the conductance of implanted rat muscle AChR-channels was 38 pS and that of sodium channels 20 pS. The conductance of implanted Torpedo AChR channels was 40 pS. The conductance of implanted channels was similar in cell-attached and in cell-free patches.(ABSTRACT TRUNCATED AT 400 WORDS)

UI MeSH Term Description Entries
D007473 Ion Channels Gated, ion-selective glycoproteins that traverse membranes. The stimulus for ION CHANNEL GATING can be due to a variety of stimuli such as LIGANDS, a TRANSMEMBRANE POTENTIAL DIFFERENCE, mechanical deformation or through INTRACELLULAR SIGNALING PEPTIDES AND PROTEINS. Membrane Channels,Ion Channel,Ionic Channel,Ionic Channels,Membrane Channel,Channel, Ion,Channel, Ionic,Channel, Membrane,Channels, Ion,Channels, Ionic,Channels, Membrane
D008564 Membrane Potentials The voltage differences across a membrane. For cellular membranes they are computed by subtracting the voltage measured outside the membrane from the voltage measured inside the membrane. They result from differences of inside versus outside concentration of potassium, sodium, chloride, and other ions across cells' or ORGANELLES membranes. For excitable cells, the resting membrane potentials range between -30 and -100 millivolts. Physical, chemical, or electrical stimuli can make a membrane potential more negative (hyperpolarization), or less negative (depolarization). Resting Potentials,Transmembrane Potentials,Delta Psi,Resting Membrane Potential,Transmembrane Electrical Potential Difference,Transmembrane Potential Difference,Difference, Transmembrane Potential,Differences, Transmembrane Potential,Membrane Potential,Membrane Potential, Resting,Membrane Potentials, Resting,Potential Difference, Transmembrane,Potential Differences, Transmembrane,Potential, Membrane,Potential, Resting,Potential, Transmembrane,Potentials, Membrane,Potentials, Resting,Potentials, Transmembrane,Resting Membrane Potentials,Resting Potential,Transmembrane Potential,Transmembrane Potential Differences
D008839 Microelectrodes Electrodes with an extremely small tip, used in a voltage clamp or other apparatus to stimulate or record bioelectric potentials of single cells intracellularly or extracellularly. (Dorland, 28th ed) Electrodes, Miniaturized,Electrode, Miniaturized,Microelectrode,Miniaturized Electrode,Miniaturized Electrodes
D009865 Oocytes Female germ cells derived from OOGONIA and termed OOCYTES when they enter MEIOSIS. The primary oocytes begin meiosis but are arrested at the diplotene state until OVULATION at PUBERTY to give rise to haploid secondary oocytes or ova (OVUM). Ovocytes,Oocyte,Ovocyte
D011061 Poly A A group of adenine ribonucleotides in which the phosphate residues of each adenine ribonucleotide act as bridges in forming diester linkages between the ribose moieties. Adenine Polynucleotides,Polyadenylic Acids,Poly(rA),Polynucleotides, Adenine
D011950 Receptors, Cholinergic Cell surface proteins that bind acetylcholine with high affinity and trigger intracellular changes influencing the behavior of cells. Cholinergic receptors are divided into two major classes, muscarinic and nicotinic, based originally on their affinity for nicotine and muscarine. Each group is further subdivided based on pharmacology, location, mode of action, and/or molecular biology. ACh Receptor,Acetylcholine Receptor,Acetylcholine Receptors,Cholinergic Receptor,Cholinergic Receptors,Cholinoceptive Sites,Cholinoceptor,Cholinoceptors,Receptors, Acetylcholine,ACh Receptors,Receptors, ACh,Receptor, ACh,Receptor, Acetylcholine,Receptor, Cholinergic,Sites, Cholinoceptive
D004553 Electric Conductivity The ability of a substrate to allow the passage of ELECTRONS. Electrical Conductivity,Conductivity, Electric,Conductivity, Electrical
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012333 RNA, Messenger RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
D012964 Sodium A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23. Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23

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