histamine test

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histamine

 [his´tah-mēn]
an amine, C5H9N3, produced by decarboxylation of histidine, found in all body tissues. It induces capillary dilation (which increases capillary permeability and lowers blood pressure); contraction of most smooth muscle tissue; increased gastric acid secretion; and acceleration of the heart rate. It is also a mediator of immediate hypersensitivity. adj., adj histamin´ic.

There are three types of cellular histamine receptors : H1 receptors mediate contraction of smooth muscle and capillary dilation, and H2 receptors mediate acceleration of heart rate and promotion of gastric acid secretion. Both types mediate contraction of vascular smooth muscle. H3 receptors occur in a number of systems including the central nervous system and peripheral nerves, and are believed to play a role in regulation of the release of histamine and other neurotransmitters from neurons. Histamine is used as a diagnostic aid in testing gastric secretion and in the diagnosis of pheochromocytoma. An excess of histamine apparently is released when the body comes in contact with certain substances to which it is sensitive. This excess histamine is believed to be the final cause of hay fever, urticaria (hives), and most other allergies, as well as certain stomach upsets and some headaches.

There are two types of histamine antagonists in clinical use that act at either the H1 or the H2 receptors. Drugs such as diphenhydramine (Benadryl) and chlorpheniramine(Chlor-Trimeton) are referred to as antihistamines and act on the H1 receptors; they block the effects of histamine on vascular, bronchial, and gastrointestinal smooth muscle and on capillary permeability. They are used for relief of allergic and gastrointestinal disorders and in over-the-counter cold medicines. Drugs such as cimetidine(Tagamet) act at the H2 receptors and block stimulation of gastric acid secretion.
histamine phosphate the phosphate salt of histamine, having the same actions as the base; administered by inhalation to test airway hyperresponsiveness in diagnosis of asthma, subcutaneously as a positive control in skin testing for allergy, and as a diagnostic aid to assess production of hydrochloric acid in the stomach.
histamine test
1. a formerly used test in which histamine was injected to stimulate gastric secretion and measure output of gastric acid.
2. a formerly used test for presence of a pheochromocytoma; persons with such a tumor would show first a fall and then a marked rise in blood pressure.
3. a skin prick test used in evaluation of patients with allergies; skin responses to allergens are compared to the response to a histamine wheal.

his·ta·mine test

a test for maximal production of gastric acidity or anacidity; after preliminary administration of an antihistamine, histamine acid phosphate is injected subcutaneously in a dose of 0.04 mg/kg of body weight, followed by analysis of gastric contents.

his·ta·mine test

(his'tă-mēn test)
A test for maximal production of gastric acidity or anacidity; after preliminary administration of an antihistamine, histamine acid phosphate is injected subcutaneously, followed by analysis of gastric contents.

histamine test

1. Injection of histamine subcutaneously to stimulate gastric secretion of hydrochloric acid.
2. A test for vasomotor headache; a histamine injection precipitates the onset of a headache in persons with this disease.
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