Voltage Clamp Technique

The voltage clamp is an experimental method used by electrophysiologists to measure the ion currents through the membranes of excitable cells, such as neurons while holding the membrane voltage at a set level. A basic voltage-clamp will iteratively measure the membrane potential, and then change the membrane potential (voltage) to the desired value by adding the necessary current. This "clamps" the cell membrane at a desired constant voltage, allowing the voltage clamp to record what currents are delivered. Because the currents applied to the cell must be equal to (and opposite in charge to) the current going across the cell membrane at the set voltage, the recorded currents indicate how the cell reacts to changes in membrane potential. Cell membranes of excitable cells contain many different kinds of ion channels, some of which are voltage-gated. The voltage clamp allows the membrane voltage to be manipulated independently of the ionic currents, allowing the current-voltage relationships of membrane channels to be studied.

1. Voltage Clamp and Patch Clamp Technique 4 th November, 2019 Presented by , Shryli K S V th Semester Molecular Biology Guided by, Ms Sanjana Shajan Dept. of Molecular Biology Yuvaraja’s College (Autonomous) Mysuru

2. Contents Introduction History Instrumentation and working of Voltage Clamp technique Types of Voltage Clamp Technique Patch Clamp Technique Instrumentation and working of Patch Clamp technique Types of Patch Clamp Technique Conclusion References Acknowledgement 11/4/2019 Voltage Clamp & Patch Clamp Technique 2

3. Introduction Voltage Clamp technique is an electrophysiological technique used to record currents in biological memberanes . Excitable cells such as neuron, cardiac cells, muscle cells etc. 11/4/2019 Voltage Clamp & Patch Clamp Technique 3

4. History Hodgkin & Huxley. 1952. Revealed the action potential event. Nobel prize, 1963 Kenneth Cole and George Mormont . 1947. Squid axon. 11/4/2019 Voltage Clamp & Patch Clamp Technique 4

5. Instrumentation & Working 11/4/2019 Voltage Clamp & Patch Clamp Technique 5

6. Example 11/4/2019 Voltage Clamp & Patch Clamp Technique 6

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8. Types Axial wire technique Gap method Suction pipette method Two electrode voltage clamp Dual cell voltage clamp Single electrode voltage clamp 11/4/2019 Voltage Clamp & Patch Clamp Technique 8

9. Patch Clamp Technique It allows the recording of macroscopic whole cell or microscopic single–channel currents flowing across cell membrane. 11/4/2019 Voltage Clamp & Patch Clamp Technique 9

10. History Nehar and Sakmann developed it. Late 1970’s. Nobel Prize in 1991. Determined single channel currents across a membrane patch of a frogs skeletal muscle. 11/4/2019 Voltage Clamp & Patch Clamp Technique 10

11. Instrumentation and Working Voltage Clamp & Patch Clamp Technique 11

12. Types Cell attached Whole cell patch Outside out patch Inside out patch Perforated patch Loose patch 11/4/2019 Voltage Clamp & Patch Clamp Technique 12

13. Advantages 11/4/2019 Voltage Clamp & Patch Clamp Technique 13

14. Conclusion It allows separation of membrane ionic and capacitive current. It easier to obtain information with an uniform voltage, than when the voltage is changing. 11/4/2019 Voltage Clamp & Patch Clamp Technique 14

15. References James V Halliwell , Tim D Plant, Jon Robbins, Nick B Standen ; Voltage Clamp Technique; 2016; 19pp Harvey M Fishman, Dept. of physiology & bioinformatics; Elsevier North- Holland Scientific Publishers Ltd; 1982; 43pp Hans Reiner Polder, Martin Weskamp, Klaus Linz, Rainer Meyer; Voltage-Clamp and Patch-Clamp Techniques; In-Vitro Techniques; 52pp Dirk L. Ypey & Louis J. DeFelice; The Patch- Clamp Technique Explained and Exercised with the simple Electrical Equivalent Circuits; 55pp https:// en.wikipedia.org/wiki/Voltage_clamp www.youtube.com 11/4/2019 Voltage Clamp & Patch Clamp Technique 15

16. Acknowledgement I thank the department of Molecular Biology for providing me this opportunity to present my seminar, I express my sincere gratitude to Ms Sanjana Shajan for her continuous support and encouragement. Thank you all for your patience :) 11/4/2019 Voltage Clamp & Patch Clamp Technique 16