Patch Clamping An Introductory Guide to Patch Clamp Electrophysiology pot

[...]... The signal will die out over distance due to the signal leaking across the membrane resistance The membrane capacitance imparts a delay: any membrane potential change must first overcome a change in stored charge (either reduce it or increase it), in effect stretching membrane potential changes out over time Thus, membrane capacitance is a limiting factor in action potential propagation speed Similarly,... resistors to the recording circuit which can cause short-circuiting, so they should be made as large as possible Examples of these are discussed in Section 2.3.4 and elsewhere Resistors and capacitors A resistor and a capacitor in series form an RC circuit, which plays an important role in many equivalent circuits The speed of charging and discharging a capacitor, such as the plasma membrane, upon a change... the great possibilities of patch clamping Sakmann and Neher received the Nobel Prize in Physiology and Medicine for their work in 1991 Such has been the success of patch clamping that ‘conventional’ intracellular recording has drifted somewhat into the background, although it still has an important role to play in electrophysiology (see Section 2.3.2) Since the advent of patch clamping there has been... resistance and a capacitance, the electronic representation of a cell looks like Figure 2.7 In the case of an isolated patch of membrane, a membrane potential is not maintained so the voltage source would be left out of the diagram The extracellular + Rm Cm - Em intracellular Figure 2.7 An electronic model of the plasma membrane of an intact cell Membrane resistance Rm , capacitance Cm and membrane potential... patch clamping there has been a steady development of protocols and analysis techniques, many of which are now standard vocabulary to electrophysiologists, while others represent very specialised applications However, two singular inventions have greatly enhanced the general versatility of patch clamping These are perforated patch clamping and patch clamping in tissue, particularly brain slices Ironically,... ELECTRICAL PROPERTIES OF THE CELL MEMBRANE 15 membrane If there are fewer potassium channels open, then fewer potassium ions can flow: current is inversely proportional to resistance We can summarise the above by stating IK = Em – EK Rm, K (2:6) where IK is the potassium current, Em – EK is the driving force for potassium and Rm, K is the membrane resistance for potassium Resistances are expressed in ohm (Ω)... advent of patch clamp electrophysiology at the end of the 1970s, there has been an ever-increasing interest in the application of its power to investigate ion-channel-related bioscientific questions in unprecedented detail Whereas patch clamping was pioneered in specialist biophysical laboratories, later there was an expansion to many other fields in biology, as well as to basic research in medicine and related... the plasma membrane at rest will also be permeable to other ions, albeit to a much lesser extent, drawing the membrane potential towards their own equilibrium potentials Because all other equilibrium potentials are more positive than EK , the membrane potential will be more positive than EK , typically – 50 to – 80 mV 2.1.4 Ion channels The previous section stated that the membrane potential is caused... 2 A gating mechanism that can close the pore The gating mechanism is a change in protein conformation The conformation change can be initiated by a range of factors that are dependent on the channel species Classified according to gating factor, the three main ion channel species are listed below: • Voltage-dependent channels open or close depending on the membrane potential These channels have voltage... A is the membrane area, ε r is the dielectric constant for the membrane and d is the membrane thickness Thus, a measurement of capacitance (see Section 4.2.1) provides a good estimation of the membrane surface area under investigation! 2.2.3 Consequences of membrane capacitance The membrane capacitance plays an important role in both the physiological function of the plasma membrane and in the conduct . Patch Clamping An Introductory Guide to Patch Clamp Electrophysiology Areles Molleman University of Hertfordshire, UK Patch Clamping Patch Clamping An. Road, Etobicoke, Ontario, Canada M9W 1L1 Library of Congress Cataloging-in-Publication Data Molleman, Areles. Patch clamping : an introductory guide to patch