Inflammation Flashcards
Describe Histamine characteristics - how produced, metabolised, cells that produce, how stimulated to release/inhibit release
Produced from AA histidine by histidine decarboxylase, metabolised by INMT and diamine oxidase. Mast cells, neurones, ECL, basophils, pre made in secretory granules, stimulated by incr in Ca2+ caused by IgE allergic reaction act on mast, complement proteins C3a and C5a act on mast, insect sting or trauma.
What are CVS effects of histamine, incl receptors
Vasodilation via H1 (lowered TPR), increased vascular perm via H1 (lowered BV) -> Lower BP. Increased HR via H2.
What are the effects of H1 receptor?
Vasodilation via H1 (lowered TPR), increased vascular perm via H1 (lowered BV) -> Lower BP.
Exocrine secretion via blood flow increase.
Visceral SM contraction e.g. bronchial, gut.
Algesia = pain, itchign and sneeze vi sensory nerve stim
What are the effects of H2 receptor?
Gastric acid secretion.
Increase in HR
How does histamine cause the lewis triple response?
e.g. Scratch by nail/insect bite
Red line = mast cell degran release histamine, histamine causes vasodil = local red.
Wheal = histamine causes vasc perm = swell/oedema.
Flare = Histamine act on nociceptor, antidromic signals to far away endings -> vasoactive transmitters -> vasodil as well as causes mast cell degran tf causing even more vasodil
What drugs are used to treat minor inflam reaction? give example of reactions, and Name generations of drugs
Antihistamines - H1 antagonists.
E.g. hayfever, insect bite
1st gen = mepyramine, diphenhydramine, promethazine
2nd gen = terfenodine, fexofenadine
Therapeutic and side effects of 1st gen histamine antag drugs?
reduces minor inflammatory reactions e.g. hayfever. Does not help asthma.
Promethazine is anti emetic so good for motion sickness.
Sedative so drowsy. Anti muscarinic so cause atropine like effects e.g. blurry vision and constipation.
