Editing Patch clamp (section)

==Basic technique==

=== Set-up ===
[[File:Patch Clamp Rig classic.jpg|thumb|right|Classical patch clamp setup, with [[microscope]], antivibration table, and [[micromanipulator]]s]]
During a patch clamp recording, a hollow glass tube known as a [[Pipette#Glass micropipette|micropipette]] or patch pipette filled with an electrolyte solution and a recording [[electrode]]  connected to an amplifier is brought into contact with the membrane of an [[Cell isolation|isolated cell]].  Another electrode is placed in a bath surrounding the cell or tissue as a reference [[Ground (electricity)|ground]] electrode. An electrical circuit can be formed between the recording and reference electrode with the cell of interest in between.

[[File:Pipette Puller-en.svg|thumb|left|Schematic depiction of a pipette puller device used to prepare micropipettes for patch clamp and other recordings]]
[[File:Patch clamp schematic 1.png|thumb|Circuit formed during whole-cell or perforated patch clamp]]
The solution filling the patch pipette might match the ionic composition of the bath solution, as in the case of cell-attached recording, or match the [[cytoplasm]], for whole-cell recording. The solution in the bath solution may match the physiological extracellular solution, the cytoplasm, or be entirely non-physiological, depending on the experiment to be performed. The researcher can also change the content of the bath solution (or less commonly the pipette solution) by adding ions or drugs to study the ion channels under different conditions.

Depending on what the researcher is trying to measure, the diameter of the pipette tip used may vary, but it is usually in the [[micrometre|micrometer]] range.<ref name=Bannister>{{cite book|last1=Bannister|first1=Niel|editor1-last=Langton|editor1-first=Phil|title=Essential Guide to Reading Biomedical Papers: Recognizing and Interpreting Best Practice|date=November 1, 2012|publisher=Wiley-Blackwell|isbn=9781118402184|doi=10.1002/9781118402184}}</ref> This small size is used to enclose a [[cell membrane]] surface area or "patch" that often contains just one or a few ion channel molecules.<ref name= Sakamann>{{cite journal|last1=Sakmann|first1=B.|last2=Neher|first2=E.|title=Patch clamp techniques for studying ionic channels in excitable membranes|journal=Annual Review of Physiology|date=1984|volume=46|pages=455–472|doi=10.1146/annurev.ph.46.030184.002323|pmid=6143532|hdl=21.11116/0000-0000-D552-3|hdl-access=free}}</ref> This type of electrode is distinct from the "sharp microelectrode" used to puncture cells in traditional [[Electrophysiology#Intracellular recording|intracellular recordings]], in that it is sealed onto the surface of the cell membrane, rather than inserted through it.

[[File:Patch clamp schematic 2.png|thumb|left|Typical equipment used during classical patch clamp recording]]
In some experiments, the micropipette tip is heated in a microforge to produce a smooth surface that assists in forming a high [[electrical resistance|resistance]] seal with the cell membrane. To obtain this high resistance seal, the micropipette is pressed against a cell membrane and suction is applied. A portion of the cell membrane is suctioned into the pipette, creating an [[omega]]-shaped area of membrane which, if formed properly, creates a resistance in the 10–100 [[Ohm (unit)|gigaohms]] range, called a "gigaohm seal" or "gigaseal".<ref name=Sakamann /> The high resistance of this seal makes it possible to isolate electronically the currents measured across the membrane patch with little competing [[electronic noise|noise]], as well as providing some mechanical stability to the recording.<ref>{{cite journal|last1=Sigworth|first1=Fredrick J.|last2=Neher|first2=E.|title=Single Na+ channel currents observed in cultured rat muscle cells|journal=Nature|date=October 2, 1980|volume=287|issue=5781|pages=447–449|bibcode=1980Natur.287..447S|doi=10.1038/287447a0|pmid=6253802|s2cid=4238010}}</ref>

=== Recording ===
[[File:WholeCellPatchClamp-03.jpg|thumb|right|Patch clamp of a nerve cell within a slice of brain tissue. The pipette in the photograph has been marked with a slight blue color.]]
Many patch clamp amplifiers do not use true [[voltage clamp]] circuitry, but instead are [[differential amplifier]]s that use the bath electrode to set the zero current (ground) level. This allows a researcher to keep the voltage constant while observing changes in [[Electric current|current]]. To make these recordings, the patch pipette is compared to the ground electrode. Current is then injected into the system to maintain a constant, set voltage. The current that is needed to clamp the voltage is opposite in sign and equal in magnitude to the current through the membrane.<ref name=Sakamann />

Alternatively, the cell can be [[electrophysiology#Current clamp|current clamped]] in whole-cell mode, keeping current constant while observing changes in membrane [[membrane potential|voltage]].<ref name="CoveyCarter2015">{{cite book|author1=Ellen Covey|author2=Matt Carter|title=Basic Electrophysiological Methods|url=https://books.google.com/books?id=-udcBgAAQBAJ&pg=PA22|year=2015|publisher=Oxford University Press|isbn=978-0-19-993980-0|pages=22–}}</ref>


===Tissue sectioning===
Accurate tissue sectioning with 
[[Vibratome|compresstome vibratome]] or microtomes is essential, in addition to patch clamp methods. By supplying thin, uniform tissue slices, these devices provide optimal electrode implantation. To prepare tissues for patch clamp studies in a way that ensures accurate and dependable recordings, researchers can select between using vibratomes for softer tissues and microtomes for tougher structures.<ref>{{cite journal | pmid=2560557 | date=1989 | last1=Sakmann | first1=B. | last2=Edwards | first2=F. | last3=Konnerth | first3=A. | last4=Takahashi | first4=T. | title=Patch clamp techniques used for studying synaptic transmission in slices of mammalian brain | journal=Quarterly Journal of Experimental Physiology | volume=74 | issue=7 | pages=1107–1118 | doi=10.1113/expphysiol.1989.sp003336 | doi-access=free | hdl=11858/00-001M-0000-002C-270A-9 | hdl-access=free }}</ref> [[Leica Biosystems]], [[Carl Zeiss AG]] are the notable producer of these devices.