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Questions and Answers
What is the primary function of histamine in physiological processes?
What is the primary function of histamine in physiological processes?
- To regulate gut, cardiovascular, and lung function through slow release (correct)
- To stimulate the release of peptide mediators in the periphery
- To induce anaphylaxis through mass degranulation
- To activate the H2 receptor for gastric acid secretion
Which of the following is a systemic effect of histamine release?
Which of the following is a systemic effect of histamine release?
- Hypotension and tachycardia
- Vasodilation and increased vascular permeability
- Local itching and redness
- Bronchoconstriction and spasm (correct)
What is the mechanism of action of H1 receptor antagonists?
What is the mechanism of action of H1 receptor antagonists?
- Blockade of H2 receptors to reduce gastric acid secretion
- Inhibition of histamine release from mast cells
- Inhibition of gene expression through nuclear receptor binding
- Competitive antagonism of histamine at the H1 receptor (correct)
Which of the following is a side effect of glucocorticoids?
Which of the following is a side effect of glucocorticoids?
What is the primary mechanism of action of glucocorticoids?
What is the primary mechanism of action of glucocorticoids?
What is the function of prostaglandins?
What is the function of prostaglandins?
What is the primary difference between older and newer H1 receptor antagonists?
What is the primary difference between older and newer H1 receptor antagonists?
Histamine is derived from the amino acid Tryptophan.
Histamine is derived from the amino acid Tryptophan.
H2 receptor activation leads to bronchoconstriction.
H2 receptor activation leads to bronchoconstriction.
Newer H1 receptor antagonists, such as Loratadine, can pass the blood-brain barrier.
Newer H1 receptor antagonists, such as Loratadine, can pass the blood-brain barrier.
Glucocorticoids increase PLA2 activity.
Glucocorticoids increase PLA2 activity.
Beta adrenoceptor agonists are used to treat anaphylaxis.
Beta adrenoceptor agonists are used to treat anaphylaxis.
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Study Notes
Histamine
- Derived from Histidine, found in Mast Cells, Basophils, and Neutrophils
- Secretion by slow release is physiologically important for gut, cardiovascular, and lung function
- Mass degranulation activated in response to activated antibody leads to anaphylaxis → mass drop in blood pressure
Histamine Receptors
- H1 receptor activation:
- Bronchoconstriction
- Contraction of gut
- Vasodilation & ↑vascular permeability, dec.bp
- Stimulation of sensory nerves and release of peptide mediators in periphery → vasodilation
- H2 receptor activation:
- Gastric acid secretion
- Heart rate
- H3 receptor:
- Presynaptic nerve terminals
- H4 receptor:
- Mast cells
Histamine Release
- Local:
- Itching
- Redness
- Swelling
- Oedema
- Headache
- Vasodilation
- Bronchoconstriction
- Vomiting
- Diarrhea
- Systemic:
- Huge Vasodilation
- Bronchoconstriction and spasm
Treatment of Histamine Release
- Treated with Beta adrenoceptor agonists
- Antihistamines:
- H1 receptor antagonists
- Older (can pass BBB): Promethazine, chlorpheniramine
- Also anti-muscarinic- sedative effects
- Newer (reduced muscarinic, don't pass BBB): Loratadine, fexofenadine
- Uses: anti-allergy, sedation, cough/cold remedies, antiemetic
- Side effects: Dry mouth, blurred vision, sedation
Steroids
- Glucocorticoids:
- Prednisone
- Beclametasone
- Gene expression changes:
- Decrease PLA2 activity
- Decrease COX expression
- Side effects:
- Diabetes
- Osteoporosis
- Peptic ulcers
- Immunosuppression
- Adrenal suppression
- Altered appearance – gain weight on face and trunk, wasted limbs
- Mental disturbance
- Topical - skin atrophy, hair growth
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