9-Cholinergic Pathway Flashcards
Why are cholinergic and anticholinergic drugs limited?
They’re limited by the ubiquitous and complicated nature of cholinergic pathways- it’s hard to achieve desired therapeutic effects without adverse effects.
What is the enzyme that combines Acetyl-CoA and Choline to form Ach?
CAT (choline acetyltransferase)
What is the transporter that brings the choline molecule into the cytoplasm?
NCS (Na-Choline symporter)
What drug blocks the NCS transporter?
Hemicholinium
After Ach is synthesized, where is it stored?
Vesicles
What is the transporter that brings the Ach into the vesicle?
ATPase antiporter (takes H out)
What drug blocks the ATPase antiporter on the vesicle, thus not allowing Ach to enter vesicles to be released?
Vesamicol
An increase in what ion causes the vesicles with Ach to be released?
Ca++
What are the proteins called on the axon terminal that the vesicle binds to for it’s exocytosis?
SNARE proteins
What drug blocks SNARE proteins?
Botulinum toxin (Botox!)
After Ach does its thanggg on the postsynpatic cell, what enzyme degrades it?
Acetylcholinesterase
What is an example of a drug that inhibits acetylcholinesterase, thus increasing [Ach] in the synapse?
Physostigmine
Are nicotinic Ach receptors ligand or G-protein coupled?
Ligand
Where are nicotinic(m) Ach receptors?
Skeletal muscle
Are muscarinic Ach receptors ligand or G-protein coupled?
G-protein coupled
Are M1 receptors excitatory or inhibitory?
Excitatory
Where are M1 receptors?
Autonomic ganglia, CNS
Where are M2 receptors?
heart
Are M2 receptors excitatory or inhibitory?
Inhibitory
What is the mechanism of action of M2 receptors?
Gi coupled (inhibits AC)
Where are M3 receptors?
Smooth muscle
Are M3 receptors excitatory or inhbitory?
Excitatory
What is the mechanism of action of M1 and M3 receptors?
Gq coupled (PLC/IP3/DAG)
Where are nicotinic(n) receptors?
CNS postganglionic cell body and dendrites
How many Ach molecules are required to open the NmAchR?
2
How do the subunits of the NmAchR differ?
they each have 2 alpha, 1 beta, 1 delta, and either 1 gamma or epsilon.
What is the function of butyrylcholinesterase (BuChE)?
It’s a nonspecific cholinesterase which is less efficient than AchE.
What is the self-regulatory, + feedback loop of Ach release at the NMJ?
On the presynaptic terminal, there are receptors that bind Ach, so when Ach is released, they also bind to these receptors that trigger more Ach release. This makes sure there is a lot of Ach released into the cleft for muscle contraction.
What drug blocks the Ach + feedback receptors, thus reducing the [Ach] in the synapse?
Hexamethonium
How does the direct acting cholinergic drugs work to increase the Muscarinic receptor activity?
They cause the release of Ach from the presynaptic neuron to bind to the muscarinic receptors
How does indirect acting cholinergic drugs work to increase Ach in the synapse?
They inhibit AchE, which prevents the breakdown of Ach in the synapse.
How does atropine work?
Blocks all muscarinic receptors
What is an EPSP?
It’s a depolarization of the postsynaptic membrane, usually by the opening of NmAchR’s
Does an EPSP always result in an action potential down the sarcolemma?
No. Typically you need a handful of EPSP’s to reach threshold and cause an action potential
What is an IPSP?
It is the hyperpolarization of the postsynaptic membrane, which takes it further away from the threshold
What receptors modulate slow EPSP’s?
M1AchR’s