Module 4: ANS Pharmacology Flashcards
What is acetylcholine?
The neurotransmitter in the parasympathetic nervous system, and in the brain (learning, memory, cognition)
How is ACh transported?
VAchT (vesicular ACh Transporter) using H+-ATPase pump
What is the rate limiting step in ACh signalling?
Availability of choline
What is the source of choline in the brain?
Mostly recycled ACh or catabolism phosphatidyl-choline.
Small amount grosses BBB but does not readily cross
What causes the mobilisation of ACh vesicles towards the synaptic terminal?
An influx of calcium, triggered by an influx of sodium as the membrane potential travels down the Neuron
What is AChE?
Acetylcholinesterase - enzyme that destroys ACh in the synaptic space to control how long the ACh can exert its effect
What are autoreceptors?
“Eyes of the synapse”
Allows the pre-synaptic terminal to monitor how much ACh released.
mAChRs - muscarinic ACh receptors.
They inhibit further ACh release as feedback regulation
What are nAChRs?
Nicotinic ACh receptors - presynaptic - promote further ACh release and compete with mAChRs.
Not present on all synapses.
How do botulinum toxins work?
They are enzymes that destroy proteins responsible for vesicles release. Therefore inhibit ACh release.
It can stop muscle spasms in cerebral palsy etc
What are the core steps at any synapse?
- Dedicated neurotransmitter synthesis
- A rate-limiting step for control of synaptic action (ie choline availability)
- A method of rapid termination of signal (ie AChE)
- Means of feedback regulation (ie auto regulation)
What is a cholinergic Neuron?
A Neuron that released ACh
How many types of mAChRs are there?
Five.
What are the 5 subtypes of mAChRs?
M1, M3, M5 all activate phospholipase C.
M1- neutrons
M3 - glands/smooth muscle
M5- CNS/ salivary glands
M2 and M4 use G proteins to inhibit AdCy for cell inhibition.
M2 - cardiac
M4 - CNS
What type of receptors are mAChRs?
Metabotropic
what are some effects of muscarinic receptors?
- cardiovascular effects (slows HR, decrease CO, vasodilation
- smooth muscle (increase peristalsis, bronchoconstriction)
- secretions (promotes sweating, salivation, exocrine glands)
- eye (constricts pupillae & ciliary muscles)
What type of receptor is nAChRs?
Ionotropic
What is the general structure of nAChRs?
5 subunits in pore formation. Alpha, beta and gamma subunits - BUT some have been found with all alpha subunits