Pharmacology of Sympathomimetics and Atropine

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Questions and Answers

What is the role of sympathomimetic drugs in pharmacological modulation?

They block the release of norepinephrine.

They inhibit adrenoceptor activation.

They mimic effects of endogenous catecholamines. (correct)

They exclusively target dopamine receptors.

Which of the following statements correctly describes sympatholytics?

They are antagonists of adrenoceptors. (correct)

They are a type of adrenergic receptor agonist.

They activate the sympathetic nervous system.

They enhance the action of catecholamines.

What significant discovery related to adrenaline was made in 1896 by Oliver and Schafer?

Adrenaline caused a drop in arterial pressure.

Adrenaline was discovered to act exclusively on dopamine receptors.

Adrenaline was identified as a neurotransmitter.

Adrenaline was shown to raise arterial pressure when injected intravenously. (correct)

How does the inhibition of the survival response relate to social engagement?

It promotes thriving and social interaction. Signup and view all the answers

What is the primary physiological action of endogenous catecholamines that sympathomimetic drugs aim to replicate?

Mimicking the effects of stress hormones. Signup and view all the answers

What is the primary role of the autonomic nervous system?

Maintaining physiological homeostasis and responding to acute stressors Signup and view all the answers

Which effect is caused by atropine administration?

Inhibition of acetylcholine at muscarinic receptors Signup and view all the answers

What consequence might result from overadministration of atropine to a 14-year-old mare?

Increased sympathetic tone and colic signs Signup and view all the answers

What physiologic effect does atropine have on the gastrointestinal system?

Decreased motility and secretion Signup and view all the answers

In the clinical case, what was primarily indicated based on the mare's symptoms?

Colic due to overadministration of atropine Signup and view all the answers

What type of drug is atropine classified as?

Anticholinergic Signup and view all the answers

How does atropine affect the heart rate when administered?

It leads to tachycardia Signup and view all the answers

Which receptors does atropine primarily block?

Muscarinic receptors Signup and view all the answers

What is the primary reason acetylcholine is not used therapeutically?

It cannot cross the blood-brain barrier. Signup and view all the answers

Which of the following is a therapeutic use for bethanecol?

Promoting bladder contraction. Signup and view all the answers

Which drug is primarily used to cause pupil constriction during cataract surgery?

Carbachol Signup and view all the answers

What type of effects do cholinesterase inhibitors primarily produce?

Muscarinic effects. Signup and view all the answers

What distinguishes organophosphate compounds from other cholinesterase inhibitors?

They produce irreversible inhibition. Signup and view all the answers

What is the main organ system affected by carbachol and bethanecol in veterinary medicine?

Gastrointestinal system. Signup and view all the answers

Which of the following statements about methacholine is correct?

It is longer-acting than acetylcholine. Signup and view all the answers

Which of the following effects is associated with pilocarpine?

Stimulation of secretions from exocrine glands. Signup and view all the answers

What is the role of acetylcholinesterase in cholinergic transmission?

Inactivation of acetylcholine Signup and view all the answers

Which substance is synthesized from tyrosine in the adrenergic neurons?

Dopamine Signup and view all the answers

What type of receptors are adrenergic receptors classified as?

G-protein coupled receptors Signup and view all the answers

Which are the key neurotransmitters involved in the autonomic nervous system?

Acetylcholine and catecholamines Signup and view all the answers

What mechanism underlies the variety of physiological responses in the autonomic nervous system?

Interaction of specific receptors with different G proteins Signup and view all the answers

Which process is NOT involved in the release of neurotransmitters?

Ingestion of neurotransmitters by target cells Signup and view all the answers

Which stage occurs immediately after the influx of Ca2+ during neurotransmitter release?

Release of transmitter by exocytosis Signup and view all the answers

What is the main effect of drugs targeting the autonomic nervous system?

Modify interaction with receptors and neurotransmitters Signup and view all the answers

What distinguishes muscarinic cholinergic receptors from nicotinic receptors?

Muscarinic receptors are G-protein coupled and have subtypes. Signup and view all the answers

What is the function of reuptake in neurotransmitter regulation?

To remove excess neurotransmitter from the synaptic cleft Signup and view all the answers

What is the primary action of cholinesterase inhibitors on acetylcholine (ACh)?

They prevent ACh from binding to the enzyme. Signup and view all the answers

What is the primary effect of β2 agonists in the respiratory system?

Bronchodilation Signup and view all the answers

Which of the following is a physiological effect of neostigmine?

Contraction of skeletal muscle. Signup and view all the answers

Which drug is a commonly used β2 agonist for treating airway constriction in small animals?

Terbutaline Signup and view all the answers

Which condition can edrophonium help diagnose?

Myasthenia gravis. Signup and view all the answers

Which of the following adrenergic antagonists is known for irreversible binding to α-adrenergic receptors?

Phenoxybenzamine Signup and view all the answers

What is a common side effect of cholinergic drugs?

Intestinal rupture. Signup and view all the answers

What is the mechanism of action of muscarinic receptor antagonists?

They block the activation of muscarinic receptors. Signup and view all the answers

What is a significant noncardiovascular effect of nonselective α-adrenergic antagonists?

Decreased urine flow resistance Signup and view all the answers

Atropine's effect on the cardiovascular system includes:

Increased heart rate. Signup and view all the answers

Which of the following drugs is NOT a β2 agonist?

Yohimbine Signup and view all the answers

What effect does atropine have on the gastrointestinal system?

Relaxation of GI smooth muscle. Signup and view all the answers

What condition is phenoxybenzamine primarily used to manage?

Pheochromocytoma Signup and view all the answers

What is a common side effect of selective α1 antagonists?

Hypotension Signup and view all the answers

Which antimuscarinic agent is primarily used for controlling bradyarrhythmias?

Atropine. Signup and view all the answers

What is a contraindication for using atropine?

Glaucoma. Signup and view all the answers

Which β2 agonist has a longer duration of action than albuterol?

Clenbuterol Signup and view all the answers

How do selective α2 antagonists function in veterinary medicine?

Reverse sedation Signup and view all the answers

Which medication is specifically indicated for spasmodic colic in horses?

N-butylscopolamine bromide. Signup and view all the answers

Which of the following statements about cholinesterase inhibitors is true?

They are effective as antidotes for certain neuromuscular blockers. Signup and view all the answers

Which drug is a second-generation selective α1 antagonist?

Tamsulosin Signup and view all the answers

What effect do muscarinic antagonists have on respiratory secretions?

Decreased airway secretions. Signup and view all the answers

What effect does an adrenergic antagonist generally have on peripheral vascular resistance?

Decreases resistance Signup and view all the answers

In which clinical scenario might prazosin be used?

Relieving urethral spasm Signup and view all the answers

How does pyridostigmine compare to neostigmine in terms of gastrointestinal side effects?

Pyridostigmine has fewer adverse GI effects. Signup and view all the answers

Which of the following is a potential contraindication for clenbuterol use in food-producing animals?

Toxic drug residues Signup and view all the answers

Which adrenergic agonist is commonly aerosolized for acute bronchial relaxation?

Albuterol Signup and view all the answers

Study Notes

Pharmacology of the Autonomic Nervous System

The autonomic nervous system (ANS) is responsible for regulating involuntary bodily functions, like heart rate, digestion, and breathing.
The ANS has two branches: sympathetic and parasympathetic.
Sympathetic activation is often associated with "fight-or-flight" responses, increasing heart rate, blood pressure, and diverting blood flow from non-essential organs.

Introduction

Drugs affecting the ANS are frequently used in veterinary medicine.
The autonomic nervous system is a crucial component for maintaining homeostasis.

Clinical Case

A 14-year-old mare, treated for corneal ulcer with antibiotics and atropine, exhibited agitation, and tachycardia.
Excessive atropine led to concern for a possible colic diagnosis.

What is happening?

Overadministration of atropine can cause colic by systematic absorption.
Atropine is an anticholinergic agent that blocks acetylcholine (ACh) effects on muscarinic receptors.
The result is an increase in sympathetic tone, leading to increased heart rate, decreased gastrointestinal motility and secretions, and urine retention.

Autonomic Nervous System

The autonomic nervous system regulates bodily processes involuntarily, such as heart rate, digestion, and pupil dilation.
It involves two divisions, the sympathetic and parasympathetic, working together to maintain balance.

Sympathetic Activation

This system is crucial in stressful or emergency situations.
Sympathetic activation leads to increased heart rate, blood pressure, shunting of blood to skeletal muscles, and bronchodilation
These physiological effects are crucial for combating acute stressors or emergencies, though they can be detrimental with prolonged activation.

Parasympathetic Activation

During periods of rest and digestion, this system activates for energy conservation and homeostasis.
It decreases heart rate, increases Gastrointestinal motility and secretions, promotes digestion, and controls other related processes.

Cholinergic Pharmacology

Cholinergic neurons use acetylcholine (ACh) as their neurotransmitter.
Direct-acting agents stimulate cholinergic receptors.
Indirect-acting agents inhibit acetylcholinesterase (AChE).

Adrenergic Receptors (a & B)

Adrenergic receptors bind to norepinephrine and epinephrine, primarily involved in the "fight-or-flight" response.
a1 and a2 receptors typically result in smooth muscle contraction and constriction.
Beta receptors (β) typically result in relaxation and dilation.

Cholinergic Receptors (N & M)

Nicotinic (N) receptors are associated with rapid transmission of impulses.
Muscarinic (M) receptors are slow transmission targets, activating multiple cellular responses.

Pharmacological Modulation of Sympathetic System

Sympathomimetics mimic the effects of endogenous catecholamines like epinephrine.
Sympatholytics are antagonists that block these effects.

Adrenergic Agonists

Drugs that stimulate adrenergic receptors are divided into direct-acting (binding directly), indirect-acting (releasing stored), or mixed-acting.

Adrenergic Antagonists

These drugs block the effects of endogenous catecholamines.
They are further divided into alpha and beta-blockers based on their selective affinity.

Muscarinic Receptor Antagonists

These drugs block muscarinic receptor activation.
Examples include atropine and scopolamine, frequently employed in veterinary medicine for their antispasmodic effects or to facilitate diagnostic procedures.

Cholinesterase Inhibitors

These drugs slow the breakdown of acetylcholine at synapses, enhancing the parasympathetic nervous system's effects.
Can have effects on heart, eyes and gut.

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Description

Explore the fascinating world of sympathomimetic drugs and their role in pharmacological modulation. This quiz covers crucial concepts from the autonomic nervous system to the physiological effects of atropine. Test your knowledge on drug classifications, mechanisms, and historical discoveries in pharmacology.