Lab Techniques and Concepts

Question 1

AMPA receptors

Answer 1

permeable to Na+ (+55mV) and K+ (-90mV)

• slightly more permeable to Na+ than K+
• transient current

Question 2

leak K+ current

Answer 2

persistent K+ current, moderate permeability

Question 3

leak Na+ current

Answer 3

persistent Na+ current, low permeability

Question 4

tonic GABA current

Answer 4

persistent Cl- current , low permeability

Question 5

voltage-gated Na+ current

Answer 5

transient Na+ current, high permeability

Question 6

low intracellular chloride concentration results in:

Answer 6

hyperpolarized chloride Nernst potential (more outward current)

Question 7

high intracellular chloride concentration results in:

Answer 7

depolarized chloride Nernst potential (more inward currents)

Question 8

potassium chloride cotransporter 2 (KCC2)

Answer 8

maintains intracellular chloride levels (symport of chloride and potassium ions out of cell)
-KCC2-mediated chloride efflux driving force increases as intracellular chloride concentration increases

Question 9

what are 2 requirements for measuring KCC2 activity?

Answer 9

1) a method to elevate intracellular chloride levels (chloride load = increase KCC2 activity)
2) a method to track chloride gradients

Question 10

halorhodopsin

Answer 10

inward chloride pump that is activated by yellow light (595nm), can elevate chloride levels to measure KCC2 activity

Question 11

what is a method to track chloride gradients?

Answer 11

voltage clamp (halorhodopsin photocurrents transiently reduce the amplitude of GABA puff-induced currents/chloride influx)
-more positive E gaba, amplitude of current decreases

Question 12

what is the goal of electrophysiology?

Answer 12

to measure and manipulate the electrical properties of cells (voltage and current)

Question 13

voltage

Answer 13

the difference in charge between two compartments (with respect to the extracellular space)

Question 14

negative voltage

Answer 14

if inside of cell is more negative than outside of cell

Question 15

positive voltage

Answer 15

if inside of cell is more positive than outside of cell

Question 16

current

Answer 16

the movement of charge between two compartments

Question 17

inward current

Answer 17

the introduction of positive charge into the cell (cations move in, anions move out) - leads to depolarization

Question 18

outward current

Answer 18

the introduction of negative charge into the cell (cations move out, anions move in) - leads to hyperpolarization

Question 19

whole-cell electrophysiology

Answer 19

measure voltage between the extracellular and intracellular space, inject positive or negative charge, measure amount of injected current

Question 20

current clamp

Answer 20

study alterations of the membrane potential during neurological processes: injected current (we choose how much current we inject into the cell) and measure voltage

Question 21

voltage clamp

Answer 21

study the ionic currents generated by ion channels/pumps/transporters: clamp voltage (choose membrane potential that we want the cell to stay at), measure the amount of injected current required to maintain the voltage

Question 22

inject positive current

Answer 22

depolarization of membrane potential

Question 23

inject negative current

Answer 23

hyperpolarization of membrane potential

Question 24

potassium leak channels

Answer 24

outward current at -30mV, persistent

Question 25

GABA-A channels

Answer 25

outward current at -30mV, transient

Question 26

capacitive current

Answer 26

spike when clamp potential changes, direction of current same as direction of voltage change

Question 27

voltage-sensing channel

Answer 27

measures the voltage between the voltage electrode and the bath electrode

Question 28

electrode test (voltage-sensing channel)

Answer 28

inject 10nA of current, measure voltage drop (use V=IR to determine electrode resistance)

Question 29

BUZZ pushbuttons (voltage-sensing channel)

Answer 29

facilitates penetration of the cell membrane

Question 30

negative capacitance compensation (voltage-sensing channel)

Answer 30

allows you to discount the current charging the glass pipette (chloride/current entering the voltage electrode can go to the AgCl wire or to the glass pipette)

Question 31

current-sensing channel

Answer 31

depending on the settings, can 1) measure the current injected by the current electrode during voltage clamp 2) measure voltage

Question 32

clamp speed

Answer 32

refers to the time it takes for the amplifier to clamp the voltage (limited by how frequently the membrane potential is measured)

Question 33

clamp selector: off

Answer 33

the current electrode measures voltage

Question 34

clamp selector: slow

Answer 34

the current electrode measures current (clamp speed is 0.5ms)

Question 35

clamp selector: fast

Answer 35

the current electrode measures current (clamp speed is 350 us)

Question 36

gain

Answer 36

amplifies the data: every data point is multiplied by the gain (amplifies both the signal and noise)

Question 37

current clamp channel

Answer 37

delivers current into the cell

Question 38

over voltage (current-clamp channel)

Answer 38

alarm sounds if the voltage at the current electrode exceeds +/- 160V

Question 39

gain telegraph output BNCs (rear panel)

Answer 39

outputs the gain of the amplifier

Question 40

alarm switch (rear panel)

Answer 40

activates or inactivates the audible alarm for the over voltage warning

Question 41

grounds (rear panel)

Answer 41

grounds the electronic

Question 42

the voltage probe

Answer 42

connects to the voltage electrode control box, the electrode of the voltage probe must be coated with bleach (chlorine)

Question 43

current electrode cable

Answer 43

connects to the current electrode control box, the electrode of the current electrode cable must be coated with bleach (chlorine)