Doubts in Electrophysiology

11 posts / 0 new
Last post
varada77's picture
Doubts in Electrophysiology

I have certain doubts in electrophysiology. Why is the resistance of the voltmeter recording the current from the membrane kept high? What is the rationale behind it?

What are rectifying currents? How is it reduced by increasing the concentration of the electrolyte in the pipette?

What is voltage noise? How is this prevented by using a highly concentrated electrolyte solution in the pipette?

How does a concentrated electrolyte solution in the pipette provides a wider recording bandwidth?

I am new to the field of electrophysiology. During my study I had doubts regarding the above points. Please clarify so that I can understand the concepts better.

Also please tell me if there is a very good book which presents electrophysiological concepts in simple language. Thank you.

RedBull's picture
I hope that I can answer you

I hope that I can answer you satisfactorily.

Firstly, the resistance of the voltmeter is kept high in order to minimize the current passing through the voltmeter so that the energy dissipated across the voltmeter is minimized.

Regarding the rectifying current, I only know that the current can be classified into 2 types: the outward rectifier current and the inward rectifier current. You may search about the named currents and get to knoiw about their characteristics.

Meanwhile, I doubt if the rectifying current can be reduced by increasing the concentration of the electrolyte in the pipette.

I'm not sure about voltage noise.

I think if some authorized persons say that a concentrated electrolyte solution in the pipette can provide a wider recording bandwidth, then just follow his instructions and there's no need to delve into the reasons why this was done in this way as this is very time-consuming if you force yourself to be familar with all these rules.

Doctor_D's picture
ad 2) Rectification means

ad 2) Rectification means that a channel does not conduct ions in both directions symetrically, but rather favors one direction. This means that the current-voltage (IV) curve is not linear, but "bent".

If you change the reversal potential for an ion you also change the current that you get at a given voltage (except at the reversal potentioal, of course). So, you might get more current at a given voltage by adjusting your electrolyte composition, but only if the channel is able to conduct in that direction at all.

ad 3) I'm not sure what voltage noise is supposed to mean. If its about flickering of voltage-gated ion channels, then you might either use blockers for these channels or clamp the cell at voltages where the channels don't flicker.

The most quoted textbooks in electrophysiology are probably Ion Channels of Excitable Membranes by Bertil Hille and Single-Channel Recording by the Nobel laureates Neher and Sakmann.

littlebush's picture
Hi,varada77 and anyone

Hi,varada77 and anyone interested in electrophysiology but don't know much of it.I can appreciate your mentality and I suspect that most of the people in this field at the beginning will share some of such anxious feeling.Generally,electrophysiology is not easy and for most of the people who have been familiar with molecular biolgoy or cell biology,electrophysiology is quite different because it maily use physics to solve problems .The term electrophysilogy is too broad and not a well defined one so it is better to confine some specific techniques used say patch clamp if we want to clarify something and relieve the new comers' nerve .Understanding is of crucial improtance in learning the electrophysiloyg maybe any displine.You must digest anything you do not understand and do not leave anything fuzzy in your brain nesx time because it will interfer with your following learning process.Rome is not built in a day and learning electrophysilogy is a long term process.Try your best to consult any recouses you can obtain such as your mentor or someone big in the field by E-mailing them who generally are very nice.Reading books and literatures are very importance but unfortunately,no such book is perfect and on most of the situations ,you must consult several didderent books on just a very tiny topic .Different authors will give you differnet knowledge for nobody has the same viewpoint or perspective angle.I have read at least over 10 books and a myriad of papers just for patch clamp ,I have to say I just begin to know something but still unknow of much stuffs.Sometimes ,you even should systematically learn some advanced math such as calculus or statistics ,matrix ect in order to appreciate the single channel data and how to interprete them .Above are some of my sincere feeling and I hope it will point out some correct pathway for the followers.Good luck and let us attain the electrophysilogy peak and conque it.

Fraser Moss
Fraser Moss's picture
Here are a couple of books

Here are a couple of books that you were asking for

Patch Clamping: An Introductory Guide to Patch Clamp Electrophysiology
by Areles Molleman

ISBN: 047148685X

If you are complete beginner is would read the first book before starting on the next one I cite below. This 2nd book is more about the actual channels and proteins that are being studied than a "how to" for patching.

Ion Channels of Excitable Membranes (3rd Edition)
by Bertil Hille

ISBN: 0878933212

Fraser Moss
Fraser Moss's picture


Rectifying channels are channels that under equal but opposite electrochemical potentials, pass more current in one direction than they do current in the opposite direction.

i.e an inward rectifing potassium channel such as Kir2.1 will pass more inward current at +60mV than it passes outward current at -60mV.

A rectifying channel can be identified from its current-voltage relationship because it will not be a straight line. The image below shows an inward rectifer channel and its current-voltage relationship

littlebush's picture
Patch Clamping: An

Patch Clamping: An Introductory Guide to Patch Clamp Electrophysiology

Yeah,,this one is very suitable for the novice but you may need some deeper one such as single channel recording later .I have the book in electronic form and if anyone want,I am willing to share it with you.Just PM me and I will send it to you by E-mail.Good luck and help each other.

Tyro's picture
 Hello, I would like to have

 Hello, I would like to have the electronic copy. Can you please email it to me to: eval(unescape('%64%6f%63%75%6d%65%6e%74%2e%77%72%69%74%65%28%27%3c%61%20%68%72%65%66%3d%22%6d%61%69%6c%74%6f%3a%64%65%76%69%72%61%6f%30%30%39%40%67%6d%61%69%6c%2e%63%6f%6d%22%3e%64%65%76%69%72%61%6f%30%30%39%40%67%6d%61%69%6c%2e%63%6f%6d%3c%2f%61%3e%27%29%3b'))
Your help and time are greatly appreciated!

tom31's picture
Hello little bush, is it

Hello little bush, is it possible to send me the electronic copy as well? I am struggling with my electrophysiology and could do with a serious textbook to help me through

Cifuentes's picture
hello little Bush, Im very

hello little Bush, Im very interested on your book, would you please send me a copy to eval(unescape('%64%6f%63%75%6d%65%6e%74%2e%77%72%69%74%65%28%27%3c%61%20%68%72%65%66%3d%22%6d%61%69%6c%74%6f%3a%64%69%61%6e%61%2e%63%69%66%75%65%6e%74%65%73%2e%63%65%70%65%64%61%40%67%6d%61%69%6c%2e%63%6f%6d%22%3e%64%69%61%6e%61%2e%63%69%66%75%65%6e%74%65%73%2e%63%65%70%65%64%61%40%67%6d%61%69%6c%2e%63%6f%6d%3c%2f%61%3e%27%29%3b')).

thank you very much!

Fightforsight's picture
I would really appreciate the

I would really appreciate the electronic copy too. Please send it to eval(unescape('%64%6f%63%75%6d%65%6e%74%2e%77%72%69%74%65%28%27%3c%61%20%68%72%65%66%3d%22%6d%61%69%6c%74%6f%3a%70%72%61%73%69%2e%76%40%67%6d%61%69%6c%2e%63%6f%6d%2e%54%68%61%6e%6b%73%22%3e%70%72%61%73%69%2e%76%40%67%6d%61%69%6c%2e%63%6f%6d%2e%54%68%61%6e%6b%73%3c%2f%61%3e%27%29%3b'))!