Pharmacology-Cholinergics

Question 1

If one of your patients has decreased secretion of ACh at the neuromuscular junction, which receptors will be stimulated first?

Answer 1

Muscarinic receptors. Nicotinic receptors do no have as high of an affinity for ACh as muscarinic receptors do.

Question 2

What type of ACh receptors are at the effector organ? The post ganglionic neuron?

Answer 2

Muscarinic at the effector organ and nicotinic at the post ganglionic neuron.

Question 3

Where in the body might you find muscarinic receptors that don’t act the way you’d expect them to if you administered ACh?

Answer 3

Sympathetic neurons to sweat glands release ACh and cause sweating. Muscarinic receptors are also on peripheral blood vessels that result in relaxation and vasodilation when stimulated.

Question 4

Which muscarinic receptor type is found in sympathetic postganglionic neurons? Myocardium and smooth muscle? Exocrine glands and blood vessels?

Answer 4

M1= sympathetic ganglia. M2= myocardium and smooth muscle. M3= Blood vessels and exocrine glands.

Question 5

Where do most cholinergic drugs such as atropine act?

Answer 5

All muscarinic receptors, they are normally not selective.

Question 6

Why do M1,3,5 muscarinic receptors typically result in excitation?

Answer 6

G-coupled signal transduction activates phospholipase C -> PIP2 -> IP3 and DAG -> PKC and increase in Ca2+ -> excitation

Question 7

How does an M2, M4 muscarinic agonist slow heart rate?

Answer 7

Activation of these channels release G protein subunits -> disable adenylyl cyclase -> blocks pacemaker channels (Ca). It also opens K+ channels to hyper polarize the cell.

Question 8

What are the direct acting cholinergic receptor agonists?

Answer 8

ACh is not typically used clinically because acetylcholinesterase uses it up rapidly.

Question 9

A patient comes out of the operating room and experiences severe constipation and urinary retention. What is a good drug to prescribe to this patient?

Answer 9

Bethanechol. It is a specific muscarinic receptor agonist and will activate the parasympathetic nervous system.

Question 10

If you injected muscarine at the post ganglionic neuron would you see an effect?

Answer 10

No, muscarinic receptors only exist at the effector organs.

Question 11

What drug would you give to someone who ingested a poisonous mushroom?

Answer 11

Atropine. It is an anti-muscarinic drug and will decrease parasympathetic activation caused by the muscarine in the mushroom.

Question 12

What are the alkaloid cholinergics?

Answer 12

Muscarine, pilocarpine and nicotine (active at nicotinic receptors)

Question 13

What drug could you prescribe to a patient with glaucoma?

Answer 13

Piolocarpine. It stimulates parasympathetic activation of the eye and constricts the pupils, decreasing intraocular pressure.

Question 14

What side effects do you need to consider when giving a muscarinic agonist?

Answer 14

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Question 15

How does atherosclerosis result in an increase in blood pressure that is related to muscarinic receptors?

Answer 15

Stimulation of M3 receptors on vascular endothelial cells is diminished in atherosclerosis and you lose that aspect of NO production by endothelial cells to vasodilate smooth muscle.

Question 16

What cholinergic drugs are contraindicated in patients with glaucoma?

Answer 16

Anti-muscarinic drugs, these will increase intraocular pressure.

Question 17

Why do patients on antimuscarinics often complain of fevers?

Answer 17

Inhibition of muscarinic receptors makes it so patients can’t sweat and they gain internal heat.

Question 18

Why would you prefer to prescribe someone a quaternary amine over a tertiary amine anticholinergic?

Answer 18

Quaternary amines cannot enter the CNS and you can eliminate CNS side effects if you don’t want them.

Question 19

You are preparing a patient for colorectal surgery and want to limit GI activity. What drug could you prescribe that would not have any CNS activity?

Answer 19

Propantheline. It is an antimuscarinic that inhibits GI motility and secretions. It is a quaternary amine that cannot enter the CNS because of its positive charge.

Question 20

What drug is preferential in opthalmology eye exams over atropine or scopolamine?

Answer 20

Homatropine. Atropine and scopolamine can block muscarinic receptors in the eye for days, homatropine is fast acting and sometimes the patient can actually drive home.

Question 21

An elderly patient comes to see you complaining of urinary incontinence. What antimuscarinic drugs could you prescribe to help her out?

Answer 21

Oxybutynin and tolterodine.

Question 22

What are some of the atropine toxicities?

Answer 22

HOT as a hare, DRY as a bone, RED as beet, BLIND as a bat MAD as a hatter.

Question 23

How do you treat atropine toxicity?

Answer 23

Atropine is a COMPETITIVE antagonist, so you can give anticholinesterases that will increase ACh levels which can outcompete atropine at muscarinic receptors.

Question 24

You are riding in the car, reading, and begin to feel sick. What anticholinergic is often taken for motion sickness?

Answer 24

Scopolamine

Question 25

Why does someone with high levels of injected nicotine have a different response to a smoker?

Answer 25

When there is too much nicotine circulating, sodium channels remain in their inactivated recovery state. This results in smooth muscle relaxation and nerve depolarization. This is contrary to smoking which supplies low levels of nicotine that are excitatory on most receptors.

Question 26

What receptors cause postganglionic hyperpolarization and IPSP after nicotinic receptor stimulation of an action potential?

Answer 26

M2 muscarinic receptors.

Question 27

What part of the autonomic nervous system is affected by nicotine?

Answer 27

All parts. It stimulates sympathetic and parasympathetic pathways because it acts at all postganglionic neurons.

Question 28

Why did Pinocchio get sick when he smoked the cigar?

Answer 28

Nicotine acts on other receptors outside of the autonomic nervous system. In his case Pinocchio activated the emetic trigger zone that causes nausea and vomiting.

Question 29

Why do smokers tend to activate hormones that increase their blood pressure?

Answer 29

Nicotine acts on the hypothalamus and induces secretion of vasopressin (ADH) which goes on to raise blood pressure

Question 30

Why are you able to focus better after a smoke or a dip? Why are these habits addicting?

Answer 30

Nicotine stimulates the CNS and it also induces dopamine secretion that causes pleasure centers to activate.

Question 31

What clinical patients could possibly see physiological benefits from smoking?

Answer 31

Alzheimer’s = CNS stimulation. Ulcerative colitis = increased GI secretions

Question 32

You are doing a rotation in the rural areas of NC. A patient comes to see you complaining of rapid onset of nausea, salivation, vomiting, blurry vision and metal confusion. History reveals that this man works in the tobacco industry. What is your diagnosis and how do you treat this patient?

Answer 32

This patient has green tobacco sickness, a result of nicotine poisoning. You would give this patient atropine to block further parasympathetic stimulation and induce vomiting to get rid of nicotine.

Question 33

A 22 year old male comes to see you concerned that he cannot stop smoking. He says he’s tried everything from gum to patches. What drug can you prescribe to help him quit?

Answer 33

Varenicline (Chantix). It is a patrial nicotinic receptor agonist (partially activates the receptor and blocks the binding of nicotine when taken in)

Question 34

What are the competitive nicotinic antagonists that are ganglionic blocking agents?

Answer 34

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