Cholinomimetics Flashcards
What are Cholinomimetics?
Cholinomimetics are drugs that mimic the action of acetylcholine in the body - they are parasympathomimetic drugs
How is Acetylcholine synthesised?
From Acetyl-CoA + Choline
By Choline Acetyltransferase (CAT)
In Cholinergic neurones
What is ACh broken down by?
Acetylcholinesterase
Where are Muscarinic Receptors found?
Parasympathetic Effector organs
(Some SNS e.g. sweat glands)
How can muscarinic effects be abolished?
With low doses of muscarinic antagonist Atropine
What are the three main subsets of Muscarinic receptors?
M1
M2
M3
(M4 & M5 are in the CNS)
What type of receptors are muscarinic receptors?
Type 2 - G-protein coupled
Where are M1 receptors found?
- CNS - excitation
- Salivary Glands
- Stomach - stimulates release of HCl
Where are M2 receptors found?
Heart - decreases HR
Where are M3 receptors found?
- Salivary Glands
- Bronchial/Visceral Smooth Muscle
- Sweat Glands
- Eye
Are Muscarinic receptors generally excitatory or inhibitory?
Generally excitatory except M2 receptors on heart which are inhibitory
What type of G-proteins do the muscarinic receptors utilise?
- M1, M3, M5 = Gq protein-linked receptor → stimulates PLC to increase the production of IP3 and DAG
- M2, M4 = Gi protein-linked receptor → inhibitory - reduces the production of cAMP
Odds = Gq
Evens = Gi
What type of receptors are Nicotinic receptors?
Type 1 - Ligand-gated Ion channels
What are the two main types of Nicotinic receptors?
Those found in the muscle, and those found in ganglia
What are nicotinic receptors made up from?
5 subunits: Alpha, Beta, Gamma, Delta, Epsilon
Subunit makeup determines the ligand binding properties of the receptor
What subunits are Muscular nicotinic receptors comprised of?
2 alpha + beta + delta + epsilon
What subunits are ganglionic nicotinic receptors comprised of?
2 alpha + 3 beta
Are the effects of ACh stronger on muscarinic or nicotinic receptors?
Muscarinic