Cholinergic Antagonists Part 1 Flashcards
name 2 kinds of nicotinic antagonists
ganglionic blockers
neuromuscular blockers
cholinergic antagonists will cause what kind of responses?
FIGHT OR FLIGHT
will mimic sympathetic nervous systek
explain how neuromuscular blockers work
they bind to Nm receptors on the postsynaptic membrane of skeletal muscle, PREVENTING the binding of ACh
prevents motor endplate from depolarizing - muscle paralysis
explain how ganglionic blockers work
prevent ACh (released from preganglionic neuron) from binding Nn receptor on the ganglia, in both the PSNS and SNS
explain how muscarinic blockers work
prevent ACh from binding to the muscarinic receptors on smooth muscle, cardiac tissue, secretory glands, etc
explain the history of cholinergic antagonists
from Belladonna plants - Atropa Belladona (source of atropine) and Datura stramonium
preparations of belladonna were used in ancient india and the roman empire used it as poisoning
what are the 3 classes of cholinergic antagonists?
naturally occurring alkaloids
semisynthetic derivatives of these alkaloids
synthetic derivatives
*imp to know examples
name 2 naturally occuring alkaloids that are cholinergic antagonists
atropine
scopolamine
name 2 semisynthetic derivatives of atropine and scopolamine
homatropine
some quaternary ammonium derivatives
name a synthetic derivative that is a cholinergic antagonist
ipratropium — has selectivity for some subtypes of the muscarinic receptors
explain the action of muscarinic antagonists
prevent the effects of acetylcholine by blocking its binding to muscarinic receptors
these muscarinic receptors can be on effector cells at parasympathetic Neuroeffector junctions, in peripheral ganglia, and in the CNS
TRUE OR FALSE
muscarinic antagonists are not selective
FALSE
they are selective for certain subtypes
explain the metabolism and excretion of cholinergic antagonists
half of the drug is excreted UNCHANGED in the urine (bc so hydrophilic)
the other half is hydrolyzed and conjugated and ecreted
thus, the effects are gone very quickly in all organs EXCEPT THE EYE
the effect on iris + ciliary muscles may last over 72 hours
explain the mechanism of action of atropine
a competitive (reversible) blockade of ACh at muscarinic receptors
prevents the release of IP3 and prevents the inhibition of adenylyl cyclase (M1, M3, M5)
true or false
atropine is not selective for its receptors
FALSE
it’s highly selective for muscarinic receptors
binds M1, M2, and M3 - not selective for subgroups, but selective for muscarinic in general
explain the effect of scopolamine and atropine on the CNS
Scopolamine has CNS affects like drowsiness and amnesia
atropine has minimal effect on the CNS. slow, long lasting sedative effects
in toxic doses, esp scopolamine can cause hallucination and coma
true or false
atropine is used to treat parkinsons disease
FALSE – used to decrease the TREMORS that result from parkinsons
scopolamine is used to treat…..
vestibular disturbances - motion sickness
that involves cholinergic transmissionw
what is scopolamine
a muscarinic antagonist
name 2 cholinergic inverse agonists
atropine
ipratropium
brings original action down below the baseline
true or false
atropine is highly selective for muscarinic receptors
true
selective for muscarinic receptors in general but
not selective for M1,M2,M3 – binds all 3
true or false
atropine is competitive with Ach at muscarinic receptors
TRUE
reversible and competitive
both bind to same site
true or false
scopolamine is a muscarinic antagonist
TRUE
what is mydriasis
dilation of the eye
what is cycloplegia
weakened contraction of the ciliary muscle
what drug can be used to cause mydriasis and cycloplegia?
ATROPINE ****8
true or false
atropine increase lacrimation
FALSE - decreases
that’s why used for treatment of mydriasis and cycloplegia
what is the result of atropine on the heart
causes TACHYCARDIA (fast heartbeat)
SA and AV node are very sensitive to antimuscarinics
HOW does atropine cause tachycardia
by blocking vagal slowing
true or false
atropine causes vasodilation
FALSE
vasoconstriction