Acetylcholine Flashcards
Density of ACh receptors in NMJ
10,000 per square micrometer
About how many ACh molecules in a synaptic vesicle?
7000
Single channel conductance of ACh channel when open?
30 pS
Two things which limit time course of current at NMJ
- intrinsic property of nACh receptors
2. AChE, rather than reuptake, clears ACh
EPP at NMJ lasts about
10-15ms
How do organophosphates cause paralysis?
Inhibit AChE
Causes ACh to accumulate in synapse
Cell is depolarized and thus refractory to subsequent ACh release
Graph of NMJ current with organophosphate and w/o
…
Examples of organoposphate
serine
prostigmine
IV graph of nACh receptor
…
Reverse potential of nACh receptor
0
nACh receptors conduct which ion?
Non-selective cation channel
nACh receptors have how many subunits?
5
Ligand binds nACh receptors at:
both alpha subunits
Each subunit of the nACh receptor includes:
4 TM domains and a large extracellular domain
Compare width of nACh recptot pore to voltage-gated channels
Large (non-selective)
Blocks nACh receptors
Curare
Competitively
In a muscarinic ACh receptor, ACh binds
A single site
When ACh binds muscarinic ACh receptor,
Conformational change is induced, activating G protein
This opens GIRK channel
Potassium leaves
Hyperpolarization (slows heart rate)
Muscarinic ACh receptor has _ TMD
7
8ms
Fastest slow synaptic transmission
10-100ms
General time range for slow synaptic transmission