Transmitter Release

Question 1

What is the general mechanism of transmitter release?

Answer 1

1. Depolarizing action potential arrives at presynaptic terminal
2. Voltage-gated calcium channels open
3. There is an influx of calcium
4. Vesicles fuse with presynaptic membrane
5. 7,000-10,000 neurotransmitter molecules are released per vesicle

Question 2

What is the concentration of calcium outside vs inside the cell?

Answer 2

1-2 mM outside; 0.1 uM inside

Question 3

What is the charge of a calcium ion?

Answer 3

2+

Question 4

How many vesicles fuse with the presynaptic membrane?

Answer 4

1-300 vesicles

Question 5

What are the techniques that people use to analyze neurotransmitter release?

Answer 5

1. Electrophysiological Recordings (postsynaptic potentials, membrane capacitance, and voltametry)
2. Light and Electron Microscopy

Question 6

T/F: Blocking Na and K channels blocks neurotransmitter release.

Answer 6

False. You can get neurotransmitter release if additional depolarizing current stimulus is provided

Question 7

How do you test the role of calcium

Answer 7

1. lower Ca in extracellular solution
2. measure presynaptic inward current and excitatory postsynaptic potentials at different presynaptic command voltages while voltage-gated Na and K channels are blocked with TTX and TEA
3. Ca - chelators (EGTA, EDTA, BAPTA)
4. Ca imaging (calcium sensitive dyes)
5. drugs that inhibit voltage-gated Ca channels

Question 8

What drugs block voltage-gated Ca channels?

Answer 8

conotoxin and agatoxin

Question 9

How many msec between action potental at presynaptic terminal and opening of Ca channels?

Answer 9

0.5 msec

Question 10

How many msec between opening of Ca channels and EPSP?

Answer 10

0.5 msec

Question 11

When calcium channels open, what happens to calcium concentration?

Answer 11

[Ca] inside the cell increases from 0.1 uM to 100uM

Question 12

How are vesiciles recycled?

Answer 12

1. Filling
2. Clustering
3. Docking
4. Priming
5. Fusion
6. Local reuse “Kiss and Stay”
7. Fast recycling “Kiss and Run”
8. Clathrin mediated endocytosis

Question 13

Which proteins mediate vesicle fusion?

Answer 13

SNARE proteins

Question 14

What SNARE proteins do we need to know for the exam?

Answer 14

Syntaxin, SNAP-25, Synaptobrevin, synaptotagmin

Question 15

Which SNARE proteins form a complex that helps with the fusion of the membrane?

Answer 15

Syntaxin, SNAP-25, and synaptobrevin

Question 16

Which SNARE protein binds Ca and promotes fusion of vesicle?

Answer 16

Synaptotagmin

Question 17

What toxins degrade SNARE proteins?

Answer 17

Tetanus and Botulinus