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29 Cards in this Set

  • Front
  • Back
where cholinergic transmission occurs

(at neural junctions where ACh is the neurotransmitter)
CNS, all autonomic ganglia, postganglionic terminus of parasympathetic fibers, postganglionic terminus of sympathetic-cholinergic fibers (sweat glands), adrenal medulla, and the terminus of somatic motor nerves to skeletal muscle, the myoneural junction or the motor end plate
Location of muscarinic receptors
postganglionic terminus of parasympathetic fibers, on sweat glands, and on noninnervated vascular smooth muscle
the pathway of action of Nitric Oxide
NO synthase activated to make NO from arginine--> NO activates guanylate cyclase to produce cGMP-->cGMP binds to myosin light chains to relax vascular smooth muscle (vasodilation)
paradoxical bradycardia
from activation of muscarinic receptors on the SA node (vagus nerve); expect reflex tachycardia
muscarinic agonist

used in diagnosis of asthma

asthmatics with hyperreactive airways respond with bronchoconstriction to lower concentrations
muscarinic agonist (must be resistant to ChE)

formerly used to relieve GI dysmotility syndromes such as postsurgical ileus
muscarinic agonist that has largely replaced bethanecol; used for GI dysmotility syndromes

acts upstream on the neuron to release ACh at the terminus
muscarinic agonist

used topically in the eye to relieve narrow angle glaucoma
Sphincter iridis (circular)
parasympathetic and it causes miosis (constriction)
Dilator (radial) muscle
sympathetic and causes mydriasis (dilation)
Pilocarpine activates...
muscarinic receptors on the sphincter iridis muscle to maintain relative miosis (constriction)
Ciliary muscle
controls the angle of refraction of the lens and has muscarinic receptors
When ciliary muscle contracts
it decreases the tension on the lens which rounds up of its own elasticity to accommodate for near vision (ciliospasm)
When ciliary muscle relaxes
it increases tension on the lens to flatten it and accommodate for far vision (cycloplegia)
only agonist at nicotinic junctions

used to promote smoking cessation and/or suppress signs of nicotine withdrawal

signs of nicotine poisoning: due to sympathetic discharge from adrenals and possibly sympathetic ganglia

Very rapidly acting; need to support respiration because of flaccid paralysis
Indirect acting cholingergic agonists
ChE inhibitors
2 sites of ChE
esteratic site and anionic site

when it hydrolyzes ACh, an acetyl group is very transiently bound covalently to the esteratic side...
ChE inhibitor!!!

does not form a covalent bond with the enzyme

highly charged and does NOT cross the BBB

dissipated in minutes...
Useful in the diagnosis of myasthenia gravis
Carbamate ChE inhibitors
bind covalently to the enzyme and leave behind a carbamoyl residue that hydrolyzes slowly over hours
Carbamate ChE inhibitors (2)
effects last much longer than those of edrophonium

used to treat (not diagnose) myasthenia gravis and to reverse the paralytic effects of nondepolarizing blockers of the MNJ
carbamate ChE inhibitor

uncharged and lipid soluble (crosses BBB)

was used to treat myasthenia gravis, BUT myasthenia gravis is a peripheral disease and ChE inhibitors in CNS would cause dangerous effects

Now used occasionally to treat CNS signs of muscarinic blockers
carbamate ChE inhibitor

designed with quaternary ammonium group in order to keep it out of the CNS

too little drug is inadequate to restore transmission (myasthetic crisis)

too much results in depolarization-desensitization blockade (cholingergic crisis)
what can a diagnostic dose of edrophonium distinguish between
myasthenic crisis and cholingeric order to give the right dose of neostigmine for myasthenia gravis
Organophosphate ChE inhibitors
parathion, malathion

weapons of mass destruction: sarin and soman
Mechanism of organophosphate ChE inhibitors
react covalently with the esteratic site and leave behind phosphorylated enzyme that may require hundreds of hours to hydrolyze

some of the agents split off an alkyl group at which point the phosphorylation is essentially irreversible
reactivates the cholinesterase by removing the phosphate group if given soon enough after the exposure...but it is contraindicated in carbamate ChE inhibitor poisonings
Muscarinic blocking drugs are essential...
to reverse signs of intense parasympathetic stimulation
organophosphate ChE inhibitor

once used in treatment of narrow angle glaucoma, largely replaced by other types of agents