New histamine recap (FINAL) Flashcards
What does it mean that Histamine is an autacoid
Tissue hormone; can be produced anywhere in the body
What are some other autacoids - other than histamine?
Serotonin, Bradykinin, Prostaglandins
Histamine release due to..
Inflammation
Allergy (IgE mediated)
Anaphylactic shock
Stressors; trauma, cold, hot, UV)
Toxins, meds, plants, animal proteins, insectisides
Direct degranulation of mast cells (drugs)
Released from tissues in free form
What is histamine biologically involved in
Sleep-wake mechanism
Energy metabolism
Behavior
- Feed intake, motor activity, drinking
Endocrine glands
Autonomous functions
- BP decrease (increase in rabbits)
- Body temperature increase
Vestibular function
Histamine effect in dogs & cats
Vomiting, diarrhea, salivation, blood vessel dilation, uterine contractions, hepatomegaly
Histamine effects in horse
Salivation, Lacrimation, dyspnea, colic, diarrhea
Histamine receptors H1
Mainly in SM; also in vessels, nerve cells, immune cells
1. Contraction of sm
2. Vasodilation & permeability increase
3. Release of adrenaline and Noradrenaline
Histamine receptors H2
Mainly in glands; also in sm, immunological cells
1. Relaxation of sm
2. Glandular secretion (gastric, bronchial)
3. Inotropic & chronotropic effects on heart
4. Suppression of histamine release
Histamine receptors H3
Mainly in CNS; also autoreceptor
1. Regulation of histamine & other endogenous substance release (dopamin)
Histamine receptors H4
Mainly in GI-tract & immune system cells
1. Immune response, cytokines
Endogenous antagonists of histamine
Adrenaline & noradrenaline
-Cause vasoconstriction and reduce swelling
H1 antagonists
Mainly used to treat allergies
1st gen: Sedation effect
2nd gen: lack of ^ due to lack of antimuscarinic effect and ability to cross BBB
H2 antagonists
Used mainly as antiemetic or stomach ulcers
No sedation, no significant sm relaxation
