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Pharmacology Test #2 > Cholinergic Agonists > Flashcards

Cholinergic Agonists Flashcards

1
Q

Describe the Cycle of Acetylcholine

A

ACH is synthesized in the mitochondria of neurons catalyzed by choline O-acetyltransferase

ACh is stored and released in vesicles

Action potential stimulates the release of ACh into synaptic cleft

ACh binds to muscarinic or nicotinic acetylcholine receptors

ACh is broken down by AChE and components are recycled

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2
Q

What are the 2 types of receptors that bind ACh and where are they found

A

Muscarinic - effector organs

Nicotinic - ganglion of autonomic nervous system

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3
Q

What are the 2 key actions at muscarinic sites?

A

muscarnic receptors are activated on target organs and organ function is altered by positive stimulus

bind to receptors on nerve terminals to INHIBIT relase of other neurotransmitters; alters organ function by creating negative stimulus

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4
Q

What is the difference between positive and negative response?

A

positive response = activate; contraction or release of something

negative response = relaxation

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5
Q

Where are nicotinic receptors located?

A

ganglionic level of both parasympathetic and sympathetic sides of the autonomic nervous system

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6
Q

What do nicotinic receptors do?

A

bind ACh released from pre-ganglionic neurons and pass message on to post ganglionic neurons

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7
Q

Do nicotinic receptors have inhibitory capabilities?

A

No, only relay efferent message sent from CNS

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8
Q

Where are nicotinic receptors in the somatic nervous system located?

A

at the neuromuscular junction of skeletal muscle

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9
Q

What do the nicotinic receptors in the somatic nervous system do?

A

binding of ACh –> depolarization of nerve cell or neuromuscular end plate membrane –> positive stimulus (muscle contraction)

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10
Q

What happens if there is prolonged ACh binding to nicotinic receptors in the somatic nervous system?

A

postganglionic neuron will stop firing

skeletal muscle will relax

muscle paralysis; prevents further depolarization (negative stimulus)

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11
Q

What are the 5 types of muscarinic receptors?

A

M1 - M5

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12
Q

What do each of the muscarinic receptors do?

A

M1, M3, M5 –> cellular excitation

M2 and M4 –> inhibit cellular excitability

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13
Q

Where are muscarinic receptors found?

A

Effector Organs:

Heart

Smooth Muscle

Brain

Exocrine glands

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14
Q

What are the 2 types of nicotinic receptors?

A

Nm

Nn

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15
Q

Where are Nm receptors located?

A

neuromuscular junction

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16
Q

Where are Nn receptors located?

A

CNS

Adrenal Medulla

Autonomic Ganglia

**Nn = NON muscular

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17
Q

What are the 2 groups of direct acting cholinomimetics?

A

Esters of Cholines - acetylcholine

Alkaloids - muscarine and nicatine (comes from plants)

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18
Q

Are Choline Esters lipophilic? And what consequence does this have in the body?

A

No they’re hydrophilic

Can’t cross the BBB –> don’t produce CNS side effects like sedation

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19
Q

How are choline esters classified chemically?

A

quarternary ammoniums

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20
Q

What are the characteristics of quaternary ammoniums?

A

Hydrophilic

Hydrolyzed by acetylcholinesterase (AChE)

Variations in chemical structure alter characteristics like potency and susceptibility to hydrolysis by AChE

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21
Q

How are cholinomimetic alkaloids classified chemically? What about Muscarine?

A

Tertiary amines

Muscarine = quarternary amines

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22
Q

What are the 4 examples of cholinomimetic alkaloids that are quaternary amines?

A

Muscarine

Pilocarpine

Nicotine

Lobeline

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23
Q

What are the characteristics of cholinomimetic alkaloids?

A

well absorbed after oral administration

lipid soluble –> larger volume of distribution; cross into BBB (even muscarine)

Not susceptible to acetylcholinesterase

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24
Q

What is the Mechanism of Indirect Acting Cholinomimetics

A

Act by inhibiting AChE

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25
What is the consequence of inhibiting AChE
prolongs the presence and actions of ACh @ ALL ACh-R (muscles, neurons, neural muscular junction, brain)
26
What are the 3 types of AChE inhibitors, and what are some examples?
Simple alcohols w/ a quarternary ammonium - Edrophonium Carbamate esters of alcohols with quaternary or tertiary ammonium - neostigmine, physostigmine, pyridostigmine Organophosphates - Echothiophate, Isoflurophate
27
What is the binding affinity of simple alcohols and AChE?
weak affinity --> bind weakly reversible half life = short
28
What is the binding affinity of carbamate esters and AChE?
higher affinity for AChE than simple alcohols still reversible half life = 30 minutes - 6 hour half life
29
What is the binding affinity of organophosphates and AChE?
HIGH affinity --> bind covalently very long half-life can only be overcome with new production of AChE
30
Which effector organs do direct and indirect cholinomimetics have similar effects on?
Eye Respiratory System GI tract GU tract
31
Which effector organs do direct and indirect cholinomimetics have different effects on?
CV system Secretory Glands CNS Peripheral NS Neuromuscular junction
32
What are the cholinomimetic effects on the eye?
Contraction of iris sphincter smooth muscle --> mitosis (pupillary constriction) Contraction of Ciliary muscle --> accommodation (focusing on object; muscarinics = close objects)
33
What does the contraction of the iris sphincter smooth muscle and the ciliary muscle do in the eye?
facilitate flow of aqueous humor out of anterior chamber alter amount and focus of light reaching retina
34
Which type of cholinomimetics is the eye sensitive to?
Muscarinic agonists AChE inhibitors
35
What is the clinical use of cholinomimetics in the eye?
Glaucoma --> Pilocarpine, Physostigmine
36
What is the action of cholinomimetics on glaucoma?
Muscarinic agonists/AChE inhibitors increase outflow of aqueous humor --> reduce intra-ocular pressure
37
What are the actions of cholinomimetics on the respiratory system?
contraction of smooth muscle --> restrict airflow stimulate secretions from tracheobronchial mucosa **ACh agonists aren't used much in respiratory medicine
38
What are the cholinomimetic effects on the GI tract?
Increase secretory and motor activity in the gut Stimulate salivary/gastric glands, pancreas, small intestine increase peristalsis relaxes most GI sphincters --> GI contents pass along freely
39
Clinically when would you use cholinomimetics for GI disorders?
When you want to correct depressed smooth muscle activity and increase motility Post-op ileum (neostigmine) Congenital mega colon
40
What are the cholinomimetic effects on the GU tract?
Trigger voiding of bladder stimulate detrusor muscle (contraction) and relax trigone and sphincter muscles of bladder
41
When would you clinically use cholinomimetics for GU disorders, and name 2 drugs that are used?
treat urinary retention: post-op, post pardum; spinal cord injuries; neurogenic bladder bethanecol, neostigmine
42
What are the direct cholinomimetic effects on the cardiovascular system?
reduce peripheral vascular resistance: vasodilation = reduced BP; drop in BP can cause indirect reflex increase in HR Decrease heart rate: decrease SA node firing = bradycardia, reduces cardiac output **ACh agonists not used a lot for CV medicine because their results are unpredictable**
43
What are the effects of indirect cholinomimetics on the Cardiovascular system?
Increase cholinergic activity work on sympathetic and parasympathetic nerves: negative chronotropic --> bradycardia negative inotropic (squeeze of heart) --> drop in cardiac output
44
What are the cholinomimetic effects on secretory glands?
stimulates sweat gland production --> help regulate body temp stimulate lacrimal glands stimulate nasopharyngeal glands REMEMBER: Tears, Sweat, Snot
45
What are the effects of direct cholinomimetics on the nicotinic receptors in central nervous system?
Induce tremor stimulate emesis (vomitting) stimulate respiratory center
46
What are the effects of direct cholinomimetics on the muscarinic receptors in central nervous system?
induce tremor cause hypothermia interfere w/ nociception (pain sensation)
47
What are the effects of indirect cholinomimetics on the central nervous system?
need high concentration to stimulate effect convulsions coma respiratory arrest
48
What are 2 clinical uses of cholinomemetics in the CNS?
Alzheimer's Smoking cessation
49
How would cholinomemetics help in Alzheimer's?
AChE inhibitors allow ACh to hang out in synaptic cleft for longer to reach receptors and produce effect Pallative effect, not a cure
50
How do cholinomemetics help with smoking cessation?
Direct nicotinic agonists help to decrease cravings and pleasurable effects of cigarettes
51
How do cholinomimetic's indirectly effect the peripheral nervous system?
cause discharge of both sympathetic AND parasympathetic nervous systems
52
What are some of the indirect effects of cholinomemetics on the peripheral nervous system?
Increase BP Sympathetic tachycardia or vagal induced bradycardia Parasympathetic effects on GI tract --> nausea, vomitting, diarrhea, urinary voiding
53
Describe how ACh acts @ the neuromuscular junction
ACh is released from presynaptic neurons ACh binds to nicotinic cholinergic receptors on the muscle fiber --> depolarization of muscle fiber --> contraction of skeletal muscle
54
What is the low dose effect of AChE inhibitors @ the neuromuscular junction?
prolong the effects of ACh --> increase strength of muscle contraction
55
What is the medium dose effect of AChE inhibitors @ the neuromuscular junction?
can cause muscles to fibrillate --> muscle = less effective
56
What is the high dose effect of AChE inhibitors @ the neuromuscular junction?
block muscle depolarization --> muscle paralysis
57
What is Myasthenia Gravis?
Autoimmune disorder; antibodies target nicotinic receptors --> block ACh binding
58
Which drug type is useful in treating Myasthenia Gravis and why is it an effective treatment?
AChE inhibitors are drug of choice blocks AChE and allows ACh time to find and bind receptors that aren't blocked by antibodies
59
When would you use the drug neostigmine and what does it do?
following surgery, reverses neuromuscular paralysis
60
What are the consequences of excessive anticholinergic actions?
Can be lethal in kids cause arrhythmias in adults
61
How would you want to treat anticholinergic intoxication?
AChE inhibitors want to increase amount of ACh @ receptor site
62
What is the toxicity of cholinomimetics dependent on?
Receptor type: Muscarinic vs Nicotinic Mechanism of Action: Direct cholinomimetic vs AChE inhibitor
63
What are some signs of direct muscarinic agonist toxicity?
Nausea Vomitting Diarrhea Urinary urgency Salivation Sweating Cutaneous vasodilation Bronchial Constriction
64
How would you treat direct muscarinic agonist toxicity?
Anticholinergic --> Atropine
65
What are some of the signs of acute nicotine toxicity?
Infants = vomitting (ingestion of 2 cigarettes which contain fatal dose of nicotine) Large doses: CNS stimulation (convulsions, coma, respiratory arrest) Skeletal muscle depolarization --> blockade/ respiratory paralysis hypertension/cardiac arrhythmias
66
How would you treat acute nicotine toxicity?
supportive treatment until drug is metabolized (several hours)
67
What are some of the effects of chronic nicotine toxicity?
nicotine addiction
68
What is the most common cause of toxicity caused by cholinesterase inhibitors?
pesticide exposure
69
What are some of the symptoms of cholinesterase inhibitor toxicity?
Muscarinic excess: Miosis (pupillary constriction) Salivation Sweating Bronchial constriction Diaphragm paralysis Vomitting Diarrhea Convulsions
70
How would you treat cholinesterase inhibitor toxicity?
Monitor Vital Signs Decontaminate if possible Antidote w/ parenternal atropine or pralidoxime (2-PAM) 2-PAM reactivates inhibited AChE before full covalent bond forms through "aging"

Pharmacology Test #2 (7 decks)

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