Podcast
Questions and Answers
What percentage of total body serotonin is found in enterochromaffin cells?
What percentage of total body serotonin is found in enterochromaffin cells?
Which enzyme is responsible for the metabolism of serotonin?
Which enzyme is responsible for the metabolism of serotonin?
Which physiological role is not associated with serotonin?
Which physiological role is not associated with serotonin?
Which receptor subtype of serotonin is ionic channels coupled?
Which receptor subtype of serotonin is ionic channels coupled?
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What condition is characterized by excessive excretion of 5-HIAA?
What condition is characterized by excessive excretion of 5-HIAA?
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Which of the following is a pharmacological action of serotonin?
Which of the following is a pharmacological action of serotonin?
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Which effect describes the triphasic response induced by serotonin on the cardiovascular system?
Which effect describes the triphasic response induced by serotonin on the cardiovascular system?
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Which neurotransmitter does serotonin NOT directly influence in its physiological roles?
Which neurotransmitter does serotonin NOT directly influence in its physiological roles?
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What effect does serotonin have on the gastrointestinal tract?
What effect does serotonin have on the gastrointestinal tract?
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Which receptor does buspirone primarily act on?
Which receptor does buspirone primarily act on?
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What adverse effect is commonly associated with triptans?
What adverse effect is commonly associated with triptans?
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Which of the following conditions contraindicates the use of naratriptan?
Which of the following conditions contraindicates the use of naratriptan?
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What is a significant effect of serotonin on the respiratory system in patients with carcinoid tumor?
What is a significant effect of serotonin on the respiratory system in patients with carcinoid tumor?
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Which of the following is a disadvantage of triptans?
Which of the following is a disadvantage of triptans?
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How does serotonin affect the secretion of exocrine glands?
How does serotonin affect the secretion of exocrine glands?
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Which serotonin receptor agonist is used exclusively for migraine headaches?
Which serotonin receptor agonist is used exclusively for migraine headaches?
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What was a primary reason for the withdrawal of Cisapride from the market in 2000?
What was a primary reason for the withdrawal of Cisapride from the market in 2000?
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What is the mechanism of action of Tegaserod?
What is the mechanism of action of Tegaserod?
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Which receptor does Lorcaserin primarily act on?
Which receptor does Lorcaserin primarily act on?
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What condition is Ondansetron primarily used to prevent?
What condition is Ondansetron primarily used to prevent?
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Which of the following is NOT a therapeutic use of Cyproheptadine?
Which of the following is NOT a therapeutic use of Cyproheptadine?
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What symptoms characterize serotonin syndrome?
What symptoms characterize serotonin syndrome?
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What receptor types do ergot alkaloids act upon?
What receptor types do ergot alkaloids act upon?
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Which ergot alkaloid is specifically used for post-partum hemorrhage?
Which ergot alkaloid is specifically used for post-partum hemorrhage?
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Study Notes
Serotonin (5-Hydroxytryptamine)
- Serotonin is a neurotransmitter with various physiological roles
- Serotonin agonists and antagonists have clinical applications
- About 90% of body serotonin is found in enterochromaffin cells, 8% in platelets, and 2% in the CNS
Objectives
- Describe serotonin agonists and antagonists
- Describe the uses of serotonin agonists and antagonists
- List adverse effects of serotonin agonists and antagonists
Autacoids
- Autacoids are a group of chemical substances with varied biological effects
- They are synthesized by different tissues and have localized effects
- Serotonin is one of these substances
- These substances have little to no presence in the serum
Introduction
- Serotonin is a crucial neurotransmitter with diverse physiological roles
- Serotonin agonists and antagonists are used for various clinical purposes
- Examples are in treating anxiety or migraine
Biosynthesis of Serotonin
- Serotonin is synthesized from the amino acid L-tryptophan
- This involves decarboxylation, a biochemical process
- Melatonin is a product of serotonin metabolism
Fate of Serotonin
- Serotonin is metabolized by monoamine oxidase (MAO) into 5-hydroxyindoleacetic acid (5-HIAA)
- 5-HIAA is water-soluble and can be detected in urine
- Elevated 5-HIAA levels can indicate conditions like carcinoid syndrome or ingestion of bananas, and is used diagnostically
Physiological Roles of Serotonin in the Body
- Involved in temperature regulation
- Influences appetite
- Affects pain perception
- Plays a role in carcinoid syndrome, migraine headaches, and depression
- Influences anxiety levels
- Impacts intestinal motility
- Regulates vomiting
- Involved in sleep, though it's a precursor to melatonin
- Plays a role in thinking and cognition
Too Much or Too Little Serotonin
- Excessive serotonin levels lead to potentially serious conditions (serotonin syndrome)
- Low serotonin levels correlated with depression, anxiety, and other mental health issues
Mode of Action of 5-HT
- Serotonin exerts its effects by binding to various receptor subtypes (7)
- Six subtypes are G-protein-coupled receptors
- 5-HT3 is an ion channel-coupled receptor
Pharmacologic Action of 5-HT
Effect on Cardiovascular System
- Serotonin creates a triphasic response, involving initial bradycardia (decreased heart rate), decreased cardiac output, and decreased blood pressure
- Vasoconstriction, leading to increased blood pressure
- Subsequent vasodilation in skeletal muscle vessels causes a blood pressure decrease
Effect on Respiratory System
- In healthy individuals, serotonin has a minor stimulating effect on bronchioles
- In conditions like carcinoid tumors, bronchospasm can be observed.
- Serotonin can induce hyperventilation through the chemoreceptor reflex or bronchial sensory nerve stimulation
Effect on Gastrointestinal Tract
- Serotonin strongly stimulates smooth muscle in the GI tract, raising tone and promoting peristalsis
- 5-HT4 receptor activation enhances GI motility through acetylcholine (ACh) release
Effect on Nervous System
- Serotonin acts as a neurotransmitter in the central nervous system (CNS)
- It significantly affects pain and itch sensation, influencing symptoms from insect and plant stings
Effect on Gland Secretion
- Serotonin has an inhibitory effect on exocrine gland secretions
Effect on the Uterus
- High doses of serotonin can lead to fetal distress through impaired placental blood flow
Serotonin Receptor Agonists
- Buspirone: An agonist for the 5-HT1A receptor used in anxiety treatment
- Triptans: (Almotriptan, Eletriptan, Frovatriptan, Naratriptan, Rizatriptan, Sumatriptan, Zolmitriptan) - Agonists of 5-HT1D/1B receptors, primarily for migraine
- Cisapride: A 5-HT4 agonist formerly used for GERD treatment
- Tegaserod: A partial 5-HT4 agonist used for irritable bowel syndrome (IBS) with constipation
- Dexfenfluramine: An appetite suppressant acting on 5-HT2 receptors
- Fluoxetine: An antidepressant influencing serotonin activity
- Lorcaserin: A 5-HT2C receptor agonist used for obesity treatment
Disadvantages of Triptans
- Short duration of action
- Expensive
Contraindications of Triptans
- Ischemic heart disease (IHD)
- Patients with peripheral vascular disease
- Those with severe hepatic or renal impairment
- Wolfram-Parkinson-White syndrome
Serotonin Receptor Antagonists
- Cyproheptadine: Potent 5-HT2 receptor blocker and H1 receptor blocker with sedative effects (used in cold urticaria, appetite stimulant, migrane prophylaxis)
- Ketanserin: Blocks 5-HT2A and a1-adrenergic receptors, inhibits platelet aggregation. Used in treating hypertension
- Ondansetron: Prototypical antagonist of 5-HT3 receptors, primarily used in preventing nausea and vomiting associated with surgery and chemotherapy
The Ergot Alkaloids
- Bromocriptine: Used for acromegaly and hyperprolactinemia
- Ergometrine: Used for post-partum hemorrhage (PPH)
- LSD: A hallucinogenic agent
- Methysergide: Used in migraine prophylaxis
- Dihydroergotoxin: Used in treating cerebral insufficiency/Alzheimer's
Serotonin Syndrome
- Occurs with overdose or concurrent use of serotonin-increasing drugs
- Characterized by muscle rigidity, hyperthermia, arrhythmias, hypertension, and headache
Home Work Questions
- List some 5-HT receptor antagonists
- Describe serotonin's bodily distribution
- Explain the role of 5-HT agonists in migraine treatment
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Description
This quiz covers the essential functions of serotonin, including its role as a neurotransmitter and the clinical significance of serotonin agonists and antagonists. Participants will delve into the biosynthesis, physiological roles, and adverse effects associated with these compounds. Perfect for students of pharmacology and neuroscience.
