Pharm 6 - Cholinomimetics Flashcards
What is a cholinomimetic
Drug that mimics the action of ACh
Muscarinic receptors are which ANS branch?
PNS
Muscarine is a selective agonist. What is its antagonist?
Atropine
Is more muscarine required to stimulate muscarinic receptors or Nicotinic?
Nicotinic - they are less sensitive to agonist
Where are M3 receptors located?
Salivary glands / bronchial/visceral SM / Sweat glands / eye
Where are M2 receptors located?
Heart
Where are M1 receptors located?
Salivary gland, stomach, CNS
Which M receptors are excitatory?
M1 and M3 (IP3 –> DAG)
Which M receptors are inhibitory?
M2 (cAMP)
What type of receptor are muscarinic receptors?
G protein coupled receptors
Nicotinic receptors are type 1 receptors meaning?
They are ligand gated ion channels
How many subunits do nicotinic receptors have? What does this mean?
5 subunits - means they all have some structural variation
What are 3 muscarinic effects on the eye?
- Constriction of ciliary muscle (promotes near sighted vision)
- Contraction of spincter papillae - causing pupil constriction and drainage of intraocular fluid
- Lacrimation
Where does aqueous humour drain in the eye?
Canals of Schlemm
How can intraocular pressure in eye be reduced?
Stimulate muscarinic receptors - causes contraction of sphincter pupillae
In the heart, where are M2 receptors located?
Atria and nodes
How does increased muscarinic stimulation to M2 receptors cause decreased HR and CO?
M2 stimulation = decreased cAMP conc = decreased Ca influx (decreases CO), and increased K efflux (decreased HR)
Do most blood vessels have PNS innervation?
NO
How can M3 receptors act to reduce TPR
ACh acts on M3 receptors on vascular endothelial cells - stimulates NO production
NO induces VSMC relaxation, which decreases TPR
What are muscarinic effects on non-vascular SM?
Excitatory
Lung = bronchoconstriction
Gut = increased peristalsis
Bladder = increased emptying
What are muscarinic effects on exocrine glands?
Salivation / increased bronchial secretions / increased GI secretions / increased sweating (SNS mediated)
What are the 2 types of directly acting cholinomimetic drugs?
- Choline esters (bethanechol)
2. Alkaloids (pilocarpine)
