PHARM 6: Cholinomimetics Flashcards
Define cholinomimetics.
Cholinomimetics = drugs that mimic the action of Ach in the body
- they are parasympathomimetic drugs
Describe the synthesis of Ach
- Ach = synthesized from acetyl CoA + choline
- via Choline Acetyltransferase (CAT)
- Ach is pumped into vesicles
- await signal
Describe the release of Ach
- depolarization causes opening of VGCC
- causes influx of Ca2+
- causes exocytosis of Ach
What enzyme breaks down Ach?
- acetylcholinesterase
Compare differences between muscarinic + nicotinic effects
Muscarinic effects:
- can be replicated by muscarine
- can be abolished by low doses of muscarinic antagonist ATROPINE
- corresponds to those of parasympathetic stimulation
- after atropine blockade, larger doses of Ach can induce effects similar to those caused by nicotine.
What are the three main receptor subtypes of muscarinic receptors and where are they located?
M1
- CNS
- Salivary Glands
- stomach
M2
- Heart
M3
- Salivary Glands
- Bronchial/ Visceral Smooth muscle
- sweat glands
note:
M4/5 = in CNS
Muscarinic Receptors are generally excitatory / inhibitory
the except is ____
Muscarinic Receptors are generally excitatory
the except is M2 (inhibitory)
All Muscarinic receptors = Type __ receptors
M1/3/5 =
M2/4 =
All Muscarinic receptors = Type 2 receptors
(G Protein Coupled)
M1/3/5 = Gq protein linked receptor —> stimulates PLC to increase production of IP3 + DAG
M2/4 = Gi protein linked receptor —> (inhibitory) reduces production of cAMP
odd = Gq even = Gi
Nicotinic Receptors =
_______ gated ion channels
with __ subunits
There are 2 main types of nicotinic receptor
in the _____ and in the _____
Nicotinic Receptors =
LIGAND gated ion channels
with 5 subunits
(ALPHA, BETA, GAMMA, DELTA, EPSILON)
There are 2 main types of nicotinic receptor
in the MUSCLE and in the GANGLION
What are the 3 main muscarinic effects on the eye?
- contraction of the ciliary muscle
(for near vision) - Contraction of sphincter papillae
(constricts pupil + increases drainage of intraocular fluid) - Lacrimation
(tears)
What is Glaucoma?
Glaucoma = Increase in Intraocular pressure
- can cause damage to optic nerves + retina
- can lead to blindness
What generates aqueous humour?
- generated by capillaries of the ciliary body
- flows into anterior chamber of eye
what is the role of the aqueous humour?
- to supply o2 and nutrients to lens + cornea
- as they don’t have a blood supply
Describe the drainage of aqueous humour
- diffuses forwards across the lens
- then across the cornea
- drains through canals of scheme
- back into the venous system
What happens in angle closure glaucoma?
angle between cornea + iris becomes narrowed
- this narrowing reduces drainage of intraocular fluid via the canals of schlemm
How would you treat angle closure glaucoma?
- give these patients a muscarinic agonist (stimulates muscarinic receptors)
- which causes contraction of the iris
- this opens up angle increases drainage of intracocular fluid through then canal of schlemm
What are muscarinic effects on the heart + cardiovascular system?
Where are M2 receptors specfically found?
- M2 receptors are inhibitory
- slows down the heart rate
- decreases cardiac output
- causes vasodilation
- -> causes drop in BP
M2 receptors found in atria + in both nodes.