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23 Cards in this Set
- Front
- Back
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Where are Nicotinic receptors located?
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Skeletal muscle
Autonomic ganglia Adrenal Medulla Spinal Cord Brain |
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Where are Muscarinic receptors located?
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Cardiac muscle
Salivary glands GI tract Genitourinary system Smooth muscle of blood vessels Smooth muscle of eye Brain |
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Which muscarinic receptors activate G protein i?
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M2/M4
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Which muscarinic receptors activate G protein q?
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M1/M3/M5
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What occurs secondary to M1 stimulation?
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CNS excitation
Gastric secretion |
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What happens secondary to M3 stimulation?
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Gastric secretion
Salivary secretion GI smooth muscle contraction Ocular accomodation Vasodilation |
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What happens secondary to M2 stimulation?
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Cardiac inhibition
Neural inhibition |
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Nicotinic receptors are ion channels. What are the two types of ion channels?
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Ligand and Voltage
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Describe how Ach release can be altered at the synapse.
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- Block Choline re-uptake (Hemicholinium)
- Block Ach into vesicle (Vesamicol) - Block vesicle release (Botulinum) - Block Ach from receptor (Tubocararine - non - depolarizing) - Block Ach from receptor ( Suxamethonium - Depolarizing) |
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What is the difference between depolarizing and non-depolarizing agents?
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Depolarizing - block receptor
Non-depolarizing - block Ach from presynaptic Nicotinic receptor which decreases vesicle release. |
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Direct acting cholinergic agonists are classified as these two things.
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Choline Esters
Alkaloids |
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Name 6 Direct acting cholinergic agonists.
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Acetylcholine
Methacholine Bethanechol Carbachol Cevimeline Pilocarpine |
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Name 9 Indirect acting reversible cholinergic agonists.
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Ambenomium
Donepezil Edrophonium Galantamine Neostigmine Physostigmine Pyridostigmine Rivastigmine Tacrine |
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Name 2 Indirect acting irreversible cholinergic agonists.
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Echothiophate
Isoflurophate |
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What about Methacholine makes it less susceptible to acetylcholinesterase?
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The beta methyl group
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What other effect does this methyl group create?
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Decreased Nicotinic activity
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Why is carbachol not degraded by acetylcholinesterase, but still has muscarinic and nicotinic activity?
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It has no methyl group so it retains nicotinic activity.
It has a carbonic ester which is not easily hydrolyzable by acetylcholinesterase |
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Do Choline esters effect the CNS?
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No, they are quaternary molecules and are poorly absorbed and distributed in the CNS.
Alkaloids like Muscarine and Pilocarpine are much more likely to get into the brain. |
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What is the effect of muscarinic agonists on the heart?
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Increased K channel permeability and hyperpolarization
Decreased Ca++ permeability Reduced Na++ current Pacemaker is slowed Conduction Velocity is slowed Contractility is slowed |
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Describe the NO pathway that leads to smooth muscle relaxation via the M3 receptor.
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IP3/DAG leads to increased Ca
Ca combines with calmodulin This complex stimulates NOS NOS converts arginine to NO and citrulline NO leaves the endothelial cell into the smooth muscle cell and activates guanylyl cyclase Guanylyl cyclase converts GTP to cGMP which causes relaxation. |
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What is the role of PDE5 in this process? (Phosphodiesterase)
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Phosphodiesterase degrades cGMP to 5' GMP. Sildenafil inhibits this enzyme
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How do organophosphate work?
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They have a hydrolyzable phosphate bond.
When phosphate is released, it reacts and inhibits Acetylcholinesterase. |
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What is the difference between Reversible and Non-reversible anticholinesterases?
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They bind at the same site, but reversible groups have a carbamoyl group that is transferred to the enzyme
Irreversible's have a phosphate group that is not easily hydrolyzed. |
