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Questions and Answers
What type of receptors do sympathomimetic drugs primarily target in the sympathetic nervous system?
What type of receptors do sympathomimetic drugs primarily target in the sympathetic nervous system?
Which of the following statements best describes adrenergic antagonists?
Which of the following statements best describes adrenergic antagonists?
Which drug is an example of a beta-blocker that specifically targets β1 receptors?
Which drug is an example of a beta-blocker that specifically targets β1 receptors?
Which type of drug inhibits the reuptake of norepinephrine in the sympathetic nervous system?
Which type of drug inhibits the reuptake of norepinephrine in the sympathetic nervous system?
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What is the role of muscarinic agonists in the context of acetylcholine esterase inhibitors?
What is the role of muscarinic agonists in the context of acetylcholine esterase inhibitors?
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What type of receptors do both the sympathetic and parasympathetic nervous systems utilize at the synapses between preganglionic and postganglionic neurones?
What type of receptors do both the sympathetic and parasympathetic nervous systems utilize at the synapses between preganglionic and postganglionic neurones?
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Which subunits are specifically used in the nicotinic ACh receptors of the autonomic nervous system?
Which subunits are specifically used in the nicotinic ACh receptors of the autonomic nervous system?
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Which drug is a non-competitive antagonist of autonomic nicotinic ACh receptors?
Which drug is a non-competitive antagonist of autonomic nicotinic ACh receptors?
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What effect does hexamethonium have on the autonomic nervous system?
What effect does hexamethonium have on the autonomic nervous system?
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Which type of receptors do postganglionic neurones of the parasympathetic nervous system target?
Which type of receptors do postganglionic neurones of the parasympathetic nervous system target?
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What is the primary mechanism of action for muscarinic agonists?
What is the primary mechanism of action for muscarinic agonists?
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What condition can muscarine poisoning lead to?
What condition can muscarine poisoning lead to?
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Which drug can reverse the symptoms of muscarine poisoning?
Which drug can reverse the symptoms of muscarine poisoning?
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Study Notes
Autonomic Pharmacology
- Drugs targeting the entire autonomic nervous system affect both sympathetic and parasympathetic nervous systems.
- Nicotinic ACh receptors are present at synapses between pre- and postganglionic neurons in both systems.
- Skeletal muscles also have nicotinic ACh receptors, but with a different subunit structure.
- ANS nicotinic ACh receptors use 2-7 subunits; skeletal muscle uses x1 subunits.
- Hexamethonium is a non-competitive antagonist of ANS NAChRs.
- It blocks sympathetic and parasympathetic effects, but not skeletal muscle.
- It's no longer used due to numerous side effects.
Drugs Targeting the Parasympathetic Nervous System
- Postganglionic neurons in the parasympathetic nervous system (PaNS) use muscarinic ACh receptors to affect target organs.
- Muscarinic ACh receptors are G-protein coupled with 7 transmembrane domains.
- Five types of muscarinic receptors exist with significant roles.
Muscarinic Receptors (Key Types and Functions)
- M₁: Found in the stomach and salivary glands; uses Gq, activating phospholipase C (PLC).
- M₂: Present in cardiac muscle; employs G¡, inhibiting adenylyl cyclase, reducing cAMP.
- M₃: Situated in smooth muscle (eyes, bronchi) and exocrine glands; uses Gq, activating PLC.
Muscarinic Agonists/Parasympathomimetics
- Mimic parasympathetic stimulation with effects like decreased heart rate, vasodilation, smooth muscle contraction (gut, respiratory), salivation, and tearing (lacrimation).
Muscarinic Antagonists
- Used to treat various conditions like:
- Asthma (ipratropium/tiotropium) - Relaxes bronchi
- Bradycardia (atropine) - Increases heart rate
- Constricted pupils (tropicamide) - Relaxes iris sphincter muscle, widening pupils.
- Urinary incontinence (oxybutynin/tolterodine) - Relaxes bladder muscle
- Motion sickness (hyoscine)
- Pilocarpine is an example and used to treat glaucoma.
Drugs Targeting the Sympathetic Nervous System
- Sympathetic postganglionic neurons use noradrenaline (norepinephrine) as neurotransmitter, allowing specific targeting.
- Adrenoceptors are G-protein coupled receptors with 5 main types:
- α₁: Contraction of smooth muscles (vasoconstriction) & Gq linked.
- α₂: Direct vasoconstriction, inhibits NA release, G¡ linked.
- ẞ₁: Increases heart rate and contractility, Gs linked.
- ẞ₂: Relaxation of smooth muscle (bronchi, blood vessels), Gs linked.
- ẞ₃: Relaxation of smooth muscle (bladder), Gs linked.
Catecholamine Regulation
- Noradrenaline (NA) synthesis starts with tyrosine and involves dopamine as an intermediate.
- NA is stored in vesicles and released into the synapse during action potentials.
- It gets reabsorbed by neurones using Noradrenaline transporter (NAT) protein.
- Some NA is broken down by Monoamine oxidase (MAO).
- Drugs target different steps in catecholamine regulation (NAT and MAO inhibitors).
Sympathomimetic Amines (structure similar to NA)
- These drugs share structural similarities with NA.
- They are transported into neurons via NAT and secretory vesicles.
- Displacement of NA from vesicles leads to its release and subsequent effects.
- Effects include bronchodilation, vasoconstriction, increased blood pressure, and have some euphoric effect.
- Examples include amphetamine, ephedrine, tyramine.
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Description
Test your knowledge on autonomic pharmacology, including the roles of nicotinic and muscarinic receptors. This quiz covers the effects of drugs on both sympathetic and parasympathetic nervous systems, as well as key receptor functions. Discover the intricacies of how these receptors interact with different drugs.
