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Short lived chemical mediators that play a significant role in response to local injury
Histamine is involved in (7):
- Drug Rnxs
- Gastric Secretions
H1 Histamine Receptors are responsible for:
- Smooth Muscle Contraction
- Relax small arterioles-> Decrease peripheral resistance and BP
H2 Histamine Receptors are responsible for:
Gastric Acid Secretion
H3 Histamine Receptors are responsible for:
Modulate neurotransmitter release in CNS
- Mast Cell Pool (and basophils)
- Non-Mast Cell Pool (GIT, CNS and skin)
The non-mast cell histamine pool=
What type of histamine stores are responsible for allergic reactions?
Mast cell pool
_____ histamine pool synthesizes histamine slowly, while the ____ pool synthesizes/releases it continuously
- Mast Cell Pool
- GIT, CNS and dermis
What decreases Histamine release?
Role histamine has in neurons (3):
- Stimulate sensory nerves
- Neurotransmitter in brain
- Emetic response
Role of histamine in microcirulation (2):
- Relax arterioles
- Increase Capillary permeability
Pharmacological Effects of Histamine (5):
- Smooth M Contraction
- Gastric Secretion
- Dermal Rxn
- Pharmacologic effects of histamine:
Within the cardiovascular system, histamine induces (4):
- Dilation of arterioles
- Decrease BP
- Increase Capillary Permeability- EDEMA
- Contraction of Large Vessels
Timeframe for wheal and flare rxns
- Wheal(edema)= 90 sec
- Flare(red)= 1-2 mins
Vasodilation is mediated by which receptors?
Which histamine receptors respond quickly to low doses?
Which histamine receptors respond slowly to high doses?
What does Histamine induce in rabbits?
Pressor => Prominent Constriction of arteries
Histamine effects on Smooth Muscle (4):
- Contraction of bronchial sm
- relaxation of respiratory sm
- Contraction of intestinal muscle
- Contraction of Uterine sm
Histamine induces Exocrine Glands to secrete...(5)
- Gastric (HCl)
Drugs that induce histamine release from mast cells (6):
- Curare Alkaloids
- Polypeptide Abx (polymixin)
In H1 Receptors, Histamine act through ___ to activate ____, which increases ___ & ____
- Gq Proteins
- Phospholipase C
- Inositol Triphosphate & Intracellular Ca
In H2 Receptors, Histamine acts through ___ and increases ___, which activates ___
- G-protein coupled Adenylyl Cyclase
- Protein Kinase A
In which spp does histamine induce relaxation of bronchial SM?
In which spp does histamine induce contraction of bronchial SM?
- Guinea Pig
Biotranformation of Histamine involves (2):
Therapeutic Uses of Histamine?
- Dx Achlorhydria
- Dx Pheocytochromia
- Histamine Phosphate
First Gen Antihistamines (7):
Second Gen Antihistamines (8):
Which Gen of Anti-Histamines lacks the CNS side Fx?
Which Gen of Anti-histamin crosses the BBB?
Which histamine receptors are used therapeutically?
Pharmacological Fx of Antihistamines (7):
- Bronchiolar SM Relaxation
- GI SM Relaxation
- Increased Capillary Perm
- Inhibition of itching/pain
- Induce Arterial Hypotension (antagonizes histamine through H1)
- Antiemetic Fx
Which H has a potent local anesthetic action?
General therapeutic Uses of Anti Histamines (7):
- Respiratory Disorders
Therapeutic uses of antihistamines in bovines (4):
- Gangrenous Mastitis
- Septic Mastitis
- Pregnancy toxemia
Antihistamine Side Fx (5):
- CNS Depression
- Teratogenic Fx
- Drug Tolerance
- Intestinal Disorders (anorexia, constipation, V/D)
- Antimuscarinic Fx (dry mouth, urinary retention, pupillary dilation tachycardia)
Although relatively safe, Clinical Signs of Antihistamine OD =>
Tx for Antihistamine OD:
Ultrashort acting Barbituates
Which type of antihistamines inhibit gastric secretions?
H2 = Antacids
Cromolyn Sodium Inhibits release of histamine via ____
- hyperpolarization of cells
- (Does not inhibit H1/H2 receptors)
Therapeutic uses of Cromolyn Sodium:
- Pulmonary/ Nasal allergic Rnxs
- Allergic Conjunctivitis