Lecture 3: Electrophysiology

Question 1

Define electrophysiology

Answer 1

Study of the movement of ions across cellular membranes and in biological tissues

Question 2

Describe the possible patch clamp technique recording conformations

Answer 2

Voltage clamp only!
cell-attached - pipette tip placed on membrane
inside-out - suction, pull up section, exposes inner domains
whole-cell - poke hole in membrane, leaves it intact while allowing access to internal enviro, continuous with pipette
outside-out - poke hole, break up membrane, allow ends to anneal, make extracellular accessible

Question 3

What are the advantages/disadvantages of in vivo, in vitro, and heterologous expression systems?

Answer 3

in vivo: physiologically relevant and real time, but can’t control extracellular composition, technically difficult
in vitro: can control extracellular composition, easier to work with, but less physiologically relevant
heterologous expression systems: see bigger current, control solution composition, can modify channel structure, but less physiologically relevant, some aspects of channel regulation may not exist in heterologous systems

Question 4

When do you use voltage clamp vs current clamp?

Answer 4

use voltage clamp when trying to test one channel, effects of toxins on channel, investigate permeability
use current clamp when trying to see excitability, anything about APs