Bursts of Openings in Transmitter-Activated Ion Channels

Abstract

Single-channel recording has become a widely used tool for the study of ion permeation mechanisms in biological membranes. Whereas the technique might have been considered an "art" after its introduction in 1976, it developed into a relatively simple method after it became possible to obtain high-resistance (several gigaohm) membrane-pipette seals. In the summer of 1982, a course on the technique was held at the Ettore Majorana Center for Scientific Culture in Erice, Sicily. It brought together people from most of the laboratories involved in patch clamping at that time. During the course, it became apparent that the technique had reached a state of maturity. Repeatedly, the opinion was expressed that a detailed description of all the aspects of the technique including representative examples of results should be available. We therefore asked the course instructors, as well as several other colleagues, to provide chapters on selected topics in order to produce this volume.The different variants of patch clamping were described quite extensively in an article by Hamill, Marty, Neher, Sakmann, and Sigworth (Pflugers Archiv 391:85) in 1981. Rather than repeating this survey in an introductory chapter, we chose to reprint that article in the Appendix of this volume (by permission of Springer-Verlag). The methods section will, therefore, go straight into detailed aspects of the technology. The second section on Concepts and Analysis is intended to provide an understanding of the statistical methods suitable for the interpretation and analysis of experimental results. The third section gives representative examples of patchclamp results from many of the fields to which the technique has so far been applied. We hope that this volume will prove useful to anyone who wishes to do singlechannel recording or to understand the results of such experiments.We would like to thank the Ettore Majorana Center for Scientific Culture as well as the European Molecular Biology Organization for providing and funding a pleasant nucleus for this volume. We also express our thanks to Ms.

Activation of ion channels in the frog end‐plate by high concentrations of acetylcholine.

“…These attributes are exactly what is needed for an efficient fast neurotransmitter. ACh molecules will bind rapidly because the transmitter concentration is high in the synaptic cleft, most channels will open very soon after binding (large opening rate constant, fi) and ACh will dissociate rapidly after a few openings have occurred in quick succession (see, for example, Colquhoun & Sakmann, 1983& Sakmann, , 1985. Even the high concentration of ACh in the synaptic cleft will produce little open-channel block (especially as such block becomes weaker as the postsynaptic membrane depolarizes) and the transmitter is not normally present for a sufficiently long time to produce any noticeable desensitization (but see Magleby & Palotta, 1981).…”

Anaesthetic modulation of nicotinic ion channel kinetics in bovine chromaffin cells

“…Bursts of openings separated by brief closures were analysed by first calculating a critical closed time duration (t,) below which a closure is classified as being a closure within a burst (Colquhoun & Sakmann, 1983;Clapham & Neher, 1984). This was calculated from the parameters of the two exponential components of the curve fit to each closed time histogram using an iterative computer routine.…”

Activation of acetylcholine receptor channels by covalently bound agonists in cultured rat myoballs.

“…A preliminary analysis of our recordings has revealed virtually no such gaps in recordings at frequencies < 4 kHz. The matter requires a direct comparison between recordings with tethered and reversibly bound agonists as well as analysis with the methods of Colquhoun & Sakmann (1983, 1985.…”