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31 Cards in this Set
- Front
- Back
ACh synthesis
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- ChAT is the enzyme and its superfast
- get actyl from mito and choline from HAChTS (transport system) |
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ACh release
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- AP -> Na entry -> depol,
- opens voltage-dependent Ca channels -> fusion of vesicles w/ PM and release |
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ACh metaboism
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- AChE at pre and post synaptic elements
- BtCHE - plasma cholinestrase (nonspecific) |
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Muscarinic receptors
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- on all autonomic effector cells, certain autonomic ganglion cells, and in CNS
- slow relative to nicotinic - on Cholinergic pre elements for feedback - G-protein-linked and |
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Nicotinic recetpors
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- ones of autonomic ganglion distinct from ones at NMJ
- ligand-gated ion channels - binding of ACh -> rapid net influx of Na+ and Ca2+ into the cell -> depol |
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M1, M3, and M5
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stimulate PIP2
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M2, M4
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inhibit cAMP
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N1
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for skeletal muscle
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N2
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neural
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parasympathomimetic drugs
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act as direct agonists at cholinergic receptors
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Methacholine
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- direct parasympathomimetic
- B-methyl sub makes it a muscarinic agonist - longer duration than Ach b/c is hydrolysis at 1/3 the rate as ACh - used to test for bronchial hyperactivity and asthmaha - SE after s.c. injection are hypotension, NandV, asthma attacks, heart block, SLUDS |
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Carbachol
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- direct parasympathomimetic
- a carbamate sub that protects is, so long duration - not selective - gets muscarinic of ciliary to cause miosis and open canals - so topically for glaucoma |
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Bethanechol
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- direct parasympathomimetic
- like methacholine and carbachol w/ a 13-methyl sub and a carbamate sub - long (2-3 hour) duration - selective for muscarinic – orally or s.c., it exerts only mild CV - gets mainly the GI and bladder – used to increase tone and contractions of pts intestine and bladder |
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Pilocarpine
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- direct parasympathomimetic
- plant alkaloid - selective for muscarinic - not a choline ester, sp ChEs dont work - 2-3 hour duration - topically like carbachol for glaucoma - systematically, you get usual side effects |
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Atropine
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will block or reverse the adverse effects of parasympathomimetics
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edrophonium
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- Reversible ChE Inhibitor
- short duration – used as MG diagnostic test as IV will reverse muscle weakness |
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neostigmine
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- Reversible ChE Inhibitor
- quaternary amine – wont cross BBB, so good for peripheral disorders – stimulates GI contractions and secretions, contractions of bladder, and improves neurotransmission at somatic nerves and SkM – used for intestinal and bladder atony and for MG - pyridostigmine and ambenonium replacing b/c they last longer |
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physostigmine
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- Reversible ChE Inhibitor
- tertiary amine from plant - can penetrate into CNS - topically for glaucoma |
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Reversible cholinesterase inhibitors
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- carbamyl esters that hydrolyze the ester linkage
– E site more resistant than A site, which slows the hydrolysis of Ach – the free site can regenerate so its reversible |
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Irreversible cholinesterase inhibitors
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- aka organophosphate ChEs
- inhibit AChE and plasma ChE - when it interacts, its hydrolzed, but the Pd E site is not - the free active site regenerates slowly or not at all - recovery depends on the synthesis of new enzyme |
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DFP
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- irreversalbe ChE inhibitor
– topically for glaucoma - long duration, should - overuse can lead to SLUD |
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Pralidoxime
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- use to treat an overdose of irreversible ChE inhibitors
- if used prior to aging (alkyl group more tightly bound to E site), frees enzyme to an active unit - most striking effect occurs at the NMJ - does not penetrate BBB |
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methacholine trade name
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(Provocholine)
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carbachol trade name
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(Carbastat; Isopto Carbachol)
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bethanechol trade name
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(Urecholine; Duvoid)
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pilocarpine trade name
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(Pilocar; Isopto Carpine)
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edrophonium trade name
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(Enlon; Reversol; Tensilon)
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neostigmine trade name
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(Prostigmin)
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physostigmine trade name
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(Antilirium; Isopto Eserine; Synapton)
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DFP trade name
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(Floropryl)
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pralidoxime trade name
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(Protopam)
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