cholinergic essentials
Terms
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- Pilocarpie
- south american plant, orally active used for glaucoma by eye gtts or film
- Pralidoxime
- choinesterase recativator (PAM) for organophosphate poisoining dephosphorylate AChE's to inactive dephosphorylated state
- Soman
- metabolite of echothiophate (used in nerve gas)
- cholinergic neuron
- preganglionic fibers terminating in adrenal medulla, autonomic gaglia (para and symp), post gaglionic fibers of para, innervation mm of somatic sys and CNS
- Tacrine and Donepezil
- tx Alzihmers dz, long druaiton of axn and cross bb (lipophilic) carbamate anterchlinesterases)
- Carbachol
- Glaucoma restant to AChE (longer halflife) NONSELECTIVE limited to mitotic agent for IOP; activates ciliary mm of ey (open angle) pupillary spincter for nearrow angle
- Glaucoma drugs (iop > 22)
- increase ouflow drainage of aqueous humor: pilocarpine, carbachol, physotigmine, ecothiophate
- Bethanechol
- activates Bowel and Bladder smooth mm/// methylcholine + carbachol = ACh with acetate replaed by carbamate and teh choline is methylated therfore not hydrolzed by ACh-esterase (longer t1/2) selective for Muscrinic (no nicotinic) receptors. indicated for urinary retention and post op ileus
- Pyridostigmine
- myasthenia gravis (increases endog ACh increasing strength)
- alzheimers
- loss of cholinergic neruons in termporal lobe tx'd with acetylholinesterase inhibitors: Donepezil and tacrine
- Treatment of Atropine OD
- atropine 2-4 mg q 5-10 min and antidote PAM (pralidozime) and give support
- neostigmine
- Myasthenia gravis, postop and neruogenic ileus and urinary retention, reversal of neuromuscualr juction blockade post op. medium duration .5-2 hrs (quaternary ammonium does not corss BBB into CNS) destroyed by plasma esterases
- Echothiophate
- organophosphate (non reversible) 100 hr duration of action used for glaucoma
- Rate limiting step of choline synthesis
- uptake of choline (remember choline is quant nitrogen with + charge and cant diffuse throught the membrane)
- muscarine
- mushrooms, lead to poisioning, cholinergic crisis with hypotension and asphexia
- location of muscarinic receptors
- gaglia of perpheral nervous system, automic effector organs, neruons
- Synthesis of acetylcholine and what inhibits the synthesis
- choline is tx tfrom the extracellular fluid into the cytoplasm of the cholinergic neuron by a carrier system that cotransports sodium and can be inhibited by HEMICHOLINIUM
- Hexamethonium
- selectively block nicotinic gaglionic receptors
- Paraozon and malozon
- metabolits for parathion and malathion
- Edrophonium
- Alcohol (very short acting used for dx of myasthenia gravis verses cholinergic crisis
- Tubocurarine
- selectively blocks nicotinic neuromuscular juction receptors
- Location of nicotinic receptors
- CNs, adrenal medulla, autonomic ganglia, and neuromuscular junction(Nm)
- Indirect Acting agents (AChE's) 3carbamates, 1 alcohol, 1 organophosphate
- (Carbamates) Neostigmine, Pyridostigmine, Physostigime, Edrophonium (alcohol), (irreversible organophosphates) Echothiophate
- Nicotinic receptors MOA
- ligand gated channel, biding of 2 acetycholine molecules elicits a conformation change that allows the entry of sodium ions, resulting i the depolarization of the effector cell. nicotine or ACh INITALLY STIMULATES AND THEN BLOCKS THE RECEPTOR.
- Direct acting cholinergic stimulants (the ABC's of cholinergics)
- ACh, Bethanechol, Carbachol
- Physotigmine
- Glaucoma (tertiary amine) crossses BBB (use atropine for CNS oversdose)
- recycling of choline
- choline may be recaptured by sodium-coupled high affinity uptake system that transpors the molecule back into the neuron where it is acetylated and stored until released by subsequent axn potential
- Direct Acting Cholinomimetic Alkaloids
- muscarinic receptor agonists, Muscarine Nicotine, Pilocarpine
- ACh
- broken down too quick not used clinically, decreases BP (due to exogenous ACh). limited to intraocular use to induce miois during surgery