M2: Histamine And Serotonin Flashcards by Sheng Saladaga

Histamine is formed by decarboxylation of L-histidine. What enzyme constitutes this process?

Histidine decarboxylase

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What are the metabolites of histamine?

N-methylhistamine
Methylimidazole Acetic Acid (MIAA)
Imidazole Acetic Acid (IAA)

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Which of the two forms of histamine is the major form?

Bound (inactive)

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What type of cell/s is histamine bound to?

Mast cells and Basophils

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In type I hypersensitivity, IgE causes histamine to unbind from mast cells or basophils. This process is called?

Degranulation

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The negative feedback control mechanism is mediated by which histamine receptor?

H2 receptor

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Which among the following is/are happening upon histamine release:
A. Local vasodilation
B. Leakage of plasma containing mediators of Acute inflam and antibodies
C. Chemitactic attraction for inflammatory cells
D. Inhibits release of lysosome contents
E. All of the above
F. None of the above

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Histamine may be released by __________ release and _______ _______ release

Immunologic Release

Chemical and Mechanical Release

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Among the two ways that histamine is released, which is exhibited by morphine?

Chemical and Mechanical

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Which among the two ways in histamine release is not associated with degranulation?

Chemical and Mechanical release

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This is an experimental drug that selectively releases histamine from tissue mast cells

Compound 48/80

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The action of compound 48/80 in tissue mast cells require ______ and _____

Energy and calcium

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Among the 4 histaminic receptors, which of them is/are seen in the postsynaptic membranes of the brain?

H1 and H2

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Among the 4 histaminic receptors, which of them is/are seen in the presynaptic membranes of the brain?

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Stimulation of this histaminic receptor/s causes cAMP to INCREASE

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Stimulation of this histaminic receptor/s causes cAMP to DECREASE

H3 and H4

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Stimulation of this histaminic receptor/s causes IP3 and DAG to INCREASE

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Which among the following analogy between the receptor and its postreceptor is not TRUE:
A. H1:Gq
B. H2:Gs
C. H3:Gi
D. H4:Gi
E. All of the above
F. None of the above

E. (Check Table16-1, pg275 :>)

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This drug is a partially selective agonist at H4 and also an inverse agonist at H3

Clobenpropit

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The following are effects of histamine release EXCEPT:
A. Stimulates pain and itching
B. Decrease sytolic and diastolic pressure
C. Bronchoconstriction
D. All of the above
E. None of the above

E. Lahat effect ng histamine

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Which among the following is NOT true among histamine administration?
A. Causes vasodilation through H1 receptor activation in large doses
B. Causes vasodilation through H2 receptor activation in small doses
C. All of the above
D. None of the above

C. Baliktad yung dalawa
H1 receptor in small doses
H2 receptor in large doses

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Which of the following is/are TRUE?
A. H1:contraction of intestinal smooth muscle
B. H2:stimulates gastric acid secretion
C. H3:nociception
D. All of the above
E. None of the above

D. All

Nociception both H1 and H3 receptors

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What is the chronologic event happening in histamine-induce edema?

Action of amine to H1 receptors in postcapillary vessels –> separation of endothelial cells –> transudation of fluid into perivascular tissue

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What is the action of histamine to the rate of contractility of the heart?

H1 = decreased contractility
H2 = increased contractility

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Which among the histaminic receptors have opposing actions, regarding gastric acid secretion, when stimulated?

H2: stimulates gastric acid secretion H3: inhibit gastric acid secretion

What is the only clinical use of histamine?

Provicative Test of Bronchial Hypereactivity

This is an H2 antagonist which has an analgesic effect

Burimamide

Histamine and serotonin drugs are known as autacoid group together with what endogenous peptides?(3)

Prostaglandin Leukotrienes Cytokines

What is the action of release inhibitors towards Antigen-IgE interaction?

Reduce degranulation of mast cells

What drug/s is/are considered as release inhibitors?

Cromolyn and Nedocromil

What experimental H3 receptor antagonist drug/s is /are potent and partially selective?

Thioperamide and Clobenpropit

Inverse agonist at H1 receptors are used in the treatment of??

Allergic conditions

What are the two types of H1 antagonists?

First and Second Generation Agents

Which H1 antagonist agent is metabolized by the CYP3A4 system?

Second generation agents

Which among the two H1 antagonist agents have a strong sedative effect and block autonomic receptors?

First Generation

This is a second generation H1 antagonist that is long acting (12-24hrs)

Meclizine

What are the two main reasons why second generation H1 antagonists are less sedative than the first-gen?

1. Less lipid soluble | 2. They are substrates of the P-glycoCHON transporter in the BBB

How does H1 antagonists and inverse agonists reduce or block the action of histamine?

By reversible competitive binding to the H1 receptor

TRUE or FALSE: The sedative effect of first-gen H1 antagonists are more intense in children than in adults.

False. They manifest excitation rather than sedation

Give 7 effects/actions of first-gen H1 antagonists

``` Sedative effect Antinausea and antiemetic action Antiparkinsonism effect Anticholinoreceptor actions Adrenoreceptor-blocking actions Serotonin blocking action Anesthetic ```

What drug is used for the tx of nausea and vomiting in pregnancy?

Doxylamine

This drug have acute supressant effects on the extrapyramidal symptoms associated in antipsychotic drugs.

Diphenhydramine

What receptor is mainly blocked by cyproheptadine?

Serotonin receptors

This is a potent H1 blocking agent. Its structure resembles phenothiazine antihistamines

Cyproheptadine

How does first-gen H1 antagonists act as local anaesthetics?

By blocking sodium channels in excitable membranes

This drug inhibit mast cell degranulation and other mediators of inflammation

Cetirizine

Give examples of first-gen antihistamines that are from ethanolamine

Carbinoxamine Dimenhydrinate Diphenhydramine

Hydroxyzine, cyclizine, and meclizine are derivatives of?

Piperazine

This antiemetic, first gen H1 blocker drug is of phenothiazine derivative

Promethazine

Give 2 main uses of second-gen H1 antagonists

Treatment of: Allergic rhinitis and Chronic Urticaria

Which of the following is/are true regarding terfenadine and astemizole when taken in combination with several antibiotics? A. Treatment for arrhythmias B. Block HERG potassium channels in the heart C. Extensively metabolized D. All of the above

B. Which contributes to repolarization of AP thereby prolonging the action potential (causing ventricular arrhythmia)

Terfenadine and astemizole are contraindicated with?

Ketoconazole, Itraconazole, Erythromycin (macrolide antibiotics) Grapefruit

``` Which of the following is NOT true A. H1 Antagonist: motion sickness B. H2 Antagonist: gastric acid secretion C. H4 antagonist: anti inflammatory D. All of the above E. None of the above ```

Serotonin is from what amino acid?

L-tryptophan

What is the chemical name for serotonin?

5-Hydroxytryptamine

Where is the second most important non neuronal site of histamine storage?

ECL Cells of the stomach fundus

What are the metabolites of 5-hydroxytryptophan?

Serotonin and enteramine

What are the important functions of serotonin? (Give 4)

Local hormone in the gut Component of platelet clotting process Role in migraine treatment Role in carcinoid syndrome treatment

Whatare the two processes involved in the synthesis of serotonin from tryptophan?

Hydroxylation of indole ring | Decarboxylation of AA

Hydroxylation at C5 of tryptophan is the rate limiting step for the synthesis of serotonin. What enzyme constitutes this process?

Tryptohan hydroxylase-1

What agents block the rate limiting enzyme in serotonin synthesis?

P-chlorophenylalanine (PCPA) | P-chloroamphetamine

Give two locations of serotonin in the body

ENterochromaffin cells in GIT, raphe nuclei of the brainstem and in platelets

What drug depletes stored serotonin?

Reserpine

``` Excretion of Which of the following substances measures serotonin synthesis? A. 5-hydroxyindoleacetaldehyde B. 5-hydroxytryptophan C. 5-hydroxyindoleacetic acid (5-HIAA) D. None of the above ```

C | Serotonin --> MAO --> 5-Hydroxyindoleaceldehyde --> aldehyde dehydrogenase --> 5-HIAA

A selective M1 and M2 agonist is prescribed to a patient with insomnia. What is this drug and what is its contraindication?

Ramelteon contraindicated with CYP1A2 inhibitors

``` Which of the following is TRUE regaring the activation of 5-HT3 receptors? A. Decrease in cardiac output B. Tachycardia C. Hypertension D. None of the above ```

A | Bradycardia and hypotension (caused by decreased cardiac output) "chemoreceptor reflex"

Which serotonin receptor subtypes decreases cAMP levels?

5-HT1A, 5HT-1B, 5-HT1D, 5HT1E, 5HT1F, 5-HT5A, 5-HT5B 5-HT1a,b,d,e,f 5-HT5a,b

What is the postrecepetor mechanism of 5-HT4,6,7 ?

Gs, increase cAMP

Ketanserin is a partially selective antagonist of which seretonin receptor subtype?

5-HT2A

What agonist act on 5-HT1P?

5-HydroxTy1ndalPine 5-hydroxyindalpine

Which receptor subtype increases IP3?

5-HT2A,B,C

Repinotan acts as an antinociceptive by stimulating which serotonin receptor subtype?

5-HT1A

What is the chemical name for serotonin?

N-acetyl-5-methoxytryptamine

Give 2 inportant roles of melatonin

Diurnal cycle in animals and sleep-wake behavior in humans

Which seeotonin receptor subtype participates in the vomiting reflex?

5-HT3

``` Stimulation of 5HT2 receptors will trigger vasoconstriction of blood vessels in which of the following? A. Skeletal muscle B. Heart C. All of the above D. None of the above ```

D. None | Powerful Vasoconstrictor in all blood vessels EXCEPT in heart and skeletal muscle

What heart condition is seen in carcinoid syndrome?

Subendocardial fibroplasia

This is a neoplasm in the enterochromaffin cells which is characterized by increased serotonin levels

Carcinoid syndrome

Stimulation of 5HT2 receptors participate in acute inflammation by what process?

Platelet aggregation

What is the effect of serotonin in the GIT?

Increase GI SM tone | Fascilitate peristalsis

A patient presents with hyperreflexia with clonus, hyperactive bowel sounds, mydriasis, and agitation. Upon history taking, you noted that the patient is taking tramadol. What is your diagnosis and what is the first line therapy?

Serotonin Syndrome | Therapy: benzodiazepines, paralysis, intubation and ventilation

What is most likely the precipitating agent/drug in Neuroleptic Malignant Syndrome? What first line therapy should you give in this syndrome?

D2-blocking antipsychotics | Diphenhydramine (parental)

Small substititions on what side chain of histamine significantly modify the selectivity of its receptor subtypes?

Imidazole ring

``` Your neighbor said she used an H1 antihistamine that was available OTC. It caused her marked drowsiness and dry mouth and she slept longer than usual. Which is the most possible drug that she used? A. Loratidine B. Levocatirizine C. Diphenhydramine D. Desloratidine ```

``` A patient has a severe ear infection associated with vertigo. Which of the following might be helpful? A. Meclizine B. Olipatidine C. Chlorphenamine D. Azelestine ```