Autacoids and Antagonists Flashcards
Histamine sources
- plant
- animal tissues
- product of venoms
- neoplasms
H1 receptors location
Smooth muscle, endothelium, brain
H2 receptors location
Gastric mucosa, cardiac, mast cells, brain
H3 receptors location
Brain
H4 receptors location
Eosinophil, neutrophil, CD4 T cells
Histamine storage
As granules (vesicles) in mast cells and basophils
Physiological funcions of histamine
- Allergic reactions (urticaria)
- Anaphylactic shock
- Gastric acid secretion
- Chemotaxis
- Neurotransmitter
- Role in immune function
Allergic reaction (urtacaria)
- Tissue oedama (vasodilation -> transudation of fluid into tissue)
- Triple response (red spot, edema, flare response)
Anaphylactic shock
- Bronchoconstriction mediated by H1 receptors
* H1 activation -> release of NO -> vasodilation -> decrease in blood pressure
Gastric acid secretion
- Contraction of intestinal smooth muscle
* Stimulate gastric acid secretion (H2)
Neurotransmitter
- Increase in HR (H2)
- Metabolic effects (increased wakefulness, decreased appetite, body temp ctrl)
- local stimulation of peripheral nerve endings (H1 and H3)
Histamine receptor antagonists pharmacological actions
- Sedation
- Anti-nausea
- Anti-parkinsonism
- Inhibit release of histamine
- Inhibit adrenergic receptors
- Inhibit serotonin receptor
- Local anaesthetic action
- Anti-cholinergic action
Histamine therapeutic uses
- Provocative test of bronchial hyperreactivity
* Positive control for allergy skin test
Urticaria medication
H1 antagonists
Atopic dermatitis
Diphenhydramine
Anaphylactic shock medication
Chlorpheniramine IV
Allergic rhinitis and chronic urticaria medication
2nd generation agents
Motion sickness medication
Scopolamine, cyclizine, meclizine