Histamine
Receptors, Histamine H1
A class of histamine receptors discriminated by their pharmacology and mode of action. Most histamine H1 receptors operate through the inositol phosphate/diacylglycerol second messenger system. Among the many responses mediated by these receptors are smooth muscle contraction, increased vascular permeability, hormone release, and cerebral glyconeogenesis. (From Biochem Soc Trans 1992 Feb;20(1):122-5)
Histamine Release
The secretion of histamine from mast cell and basophil granules by exocytosis. This can be initiated by a number of factors, all of which involve binding of IgE, cross-linked by antigen, to the mast cell or basophil's Fc receptors. Once released, histamine binds to a number of different target cell receptors and exerts a wide variety of effects.
Receptors, Histamine H2
A class of histamine receptors discriminated by their pharmacology and mode of action. Histamine H2 receptors act via G-proteins to stimulate ADENYLYL CYCLASES. Among the many responses mediated by these receptors are gastric acid secretion, smooth muscle relaxation, inotropic and chronotropic effects on heart muscle, and inhibition of lymphocyte function. (From Biochem Soc Trans 1992 Feb;20(1):122-5)
Receptors, Histamine
Cell-surface proteins that bind histamine and trigger intracellular changes influencing the behavior of cells. Histamine receptors are widespread in the central nervous system and in peripheral tissues. Three types have been recognized and designated H1, H2, and H3. They differ in pharmacology, distribution, and mode of action.
Histamine Antagonists
Drugs that bind to but do not activate histamine receptors, thereby blocking the actions of histamine or histamine agonists. Classical antihistaminics block the histamine H1 receptors only.
Histamine Agonists
Drugs that bind to and activate histamine receptors. Although they have been suggested for a variety of clinical applications histamine agonists have so far been more widely used in research than therapeutically.
Histamine H1 Antagonists
Drugs that selectively bind to but do not activate histamine H1 receptors, thereby blocking the actions of endogenous histamine. Included here are the classical antihistaminics that antagonize or prevent the action of histamine mainly in immediate hypersensitivity. They act in the bronchi, capillaries, and some other smooth muscles, and are used to prevent or allay motion sickness, seasonal rhinitis, and allergic dermatitis and to induce somnolence. The effects of blocking central nervous system H1 receptors are not as well understood.
Receptors, Histamine H3
A class of histamine receptors discriminated by their pharmacology and mode of action. Histamine H3 receptors were first recognized as inhibitory autoreceptors on histamine-containing nerve terminals and have since been shown to regulate the release of several neurotransmitters in the central and peripheral nervous systems. (From Biochem Soc Trans 1992 Feb;20(1):122-5)
Histamine H2 Antagonists
Drugs that selectively bind to but do not activate histamine H2 receptors, thereby blocking the actions of histamine. Their clinically most important action is the inhibition of acid secretion in the treatment of gastrointestinal ulcers. Smooth muscle may also be affected. Some drugs in this class have strong effects in the central nervous system, but these actions are not well understood.
Histamine N-Methyltransferase
Pyrilamine
A histamine H1 antagonist. It has mild hypnotic properties and some local anesthetic action and is used for allergies (including skin eruptions) both parenterally and locally. It is a common ingredient of cold remedies.
Methylhistamines
Histamine substituted in any position with one or more methyl groups. Many of these are agonists for the H1, H2, or both histamine receptors.
Histidine Decarboxylase
An enzyme that catalyzes the decarboxylation of histidine to histamine and carbon dioxide. It requires pyridoxal phosphate in animal tissues, but not in microorganisms. EC 4.1.1.22.
Dimaprit
Histamine H3 Antagonists
Drugs that selectively bind to but do not activate HISTAMINE H3 RECEPTORS. They have been used to correct SLEEP WAKE DISORDERS and MEMORY DISORDERS.
Histamine Agents
Cimetidine
A histamine congener, it competitively inhibits HISTAMINE binding to HISTAMINE H2 RECEPTORS. Cimetidine has a range of pharmacological actions. It inhibits GASTRIC ACID secretion, as well as PEPSIN and GASTRIN output.
Chlorpheniramine
Metiamide
A histamine H2 receptor antagonist that is used as an anti-ulcer agent.
Diphenhydramine
A histamine H1 antagonist used as an antiemetic, antitussive, for dermatoses and pruritus, for hypersensitivity reactions, as a hypnotic, an antiparkinson, and as an ingredient in common cold preparations. It has some undesired antimuscarinic and sedative effects.
Mast Cells
Granulated cells that are found in almost all tissues, most abundantly in the skin and the gastrointestinal tract. Like the BASOPHILS, mast cells contain large amounts of HISTAMINE and HEPARIN. Unlike basophils, mast cells normally remain in the tissues and do not circulate in the blood. Mast cells, derived from the bone marrow stem cells, are regulated by the STEM CELL FACTOR.
p-Methoxy-N-methylphenethylamine
A potent mast cell degranulator. It is involved in histamine release.
Basophils
Impromidine
A highly potent and specific histamine H2 receptor agonist. It has been used diagnostically as a gastric secretion indicator.
Thiourea
A photographic fixative used also in the manufacture of resins. According to the Fourth Annual Report on Carcinogens (NTP 85-002, 1985), this substance may reasonably be anticipated to be a carcinogen (Merck Index, 9th ed). Many of its derivatives are ANTITHYROID AGENTS and/or FREE RADICAL SCAVENGERS.
Guinea Pigs
Anaphylaxis
An acute hypersensitivity reaction due to exposure to a previously encountered ANTIGEN. The reaction may include rapidly progressing URTICARIA, respiratory distress, vascular collapse, systemic SHOCK, and death.
Burimamide
Histamine H1 Antagonists, Non-Sedating
A class of non-sedating drugs that bind to but do not activate histamine receptors (DRUG INVERSE AGONISM), thereby blocking the actions of histamine or histamine agonists. These antihistamines represent a heterogenous group of compounds with differing chemical structures, adverse effects, distribution, and metabolism. Compared to the early (first generation) antihistamines, these non-sedating antihistamines have greater receptor specificity, lower penetration of BLOOD-BRAIN BARRIER, and are less likely to cause drowsiness or psychomotor impairment.
Bronchial Provocation Tests
Ranitidine
A non-imidazole blocker of those histamine receptors that mediate gastric secretion (H2 receptors). It is used to treat gastrointestinal ulcers.
Triprolidine
Immunoglobulin E
An immunoglobulin associated with MAST CELLS. Overexpression has been associated with allergic hypersensitivity (HYPERSENSITIVITY, IMMEDIATE).
Cromolyn Sodium
A chromone complex that acts by inhibiting the release of chemical mediators from sensitized mast cells. It is used in the prophylactic treatment of both allergic and exercise-induced asthma, but does not affect an established asthmatic attack.
Pruritus
Terfenadine
A selective histamine H1-receptor antagonist devoid of central nervous system depressant activity. The drug was used for ALLERGY but withdrawn due to causing LONG QT SYNDROME.
Dose-Response Relationship, Drug
Famotidine
A competitive histamine H2-receptor antagonist. Its main pharmacodynamic effect is the inhibition of gastric secretion.
Amine Oxidase (Copper-Containing)
A group of enzymes including those oxidizing primary monoamines, diamines, and histamine. They are copper proteins, and, as their action depends on a carbonyl group, they are sensitive to inhibition by semicarbazide.
Gastric Juice
The liquid secretion of the stomach mucosa consisting of hydrochloric acid (GASTRIC ACID); PEPSINOGENS; INTRINSIC FACTOR; GASTRIN; MUCUS; and the bicarbonate ion (BICARBONATES). (From Best & Taylor's Physiological Basis of Medical Practice, 12th ed, p651)
Gastric Mucosa
Lining of the STOMACH, consisting of an inner EPITHELIUM, a middle LAMINA PROPRIA, and an outer MUSCULARIS MUCOSAE. The surface cells produce MUCUS that protects the stomach from attack by digestive acid and enzymes. When the epithelium invaginates into the LAMINA PROPRIA at various region of the stomach (CARDIA; GASTRIC FUNDUS; and PYLORUS), different tubular gastric glands are formed. These glands consist of cells that secrete mucus, enzymes, HYDROCHLORIC ACID, or hormones.
SRS-A
A group of LEUKOTRIENES; (LTC4; LTD4; and LTE4) that is the major mediator of BRONCHOCONSTRICTION; HYPERSENSITIVITY; and other allergic reactions. Earlier studies described a "slow-reacting substance of ANAPHYLAXIS" released from lung by cobra venom or after anaphylactic shock. The relationship between SRS-A leukotrienes was established by UV which showed the presence of the conjugated triene. (From Merck Index, 11th ed)
Gastric Acid
Hydrochloric acid present in GASTRIC JUICE.
Cetirizine
Methacholine Compounds
Pentagastrin
A synthetic pentapeptide that has effects like gastrin when given parenterally. It stimulates the secretion of gastric acid, pepsin, and intrinsic factor, and has been used as a diagnostic aid.
Ketotifen
A cycloheptathiophene blocker of histamine H1 receptors and release of inflammatory mediators. It has been proposed for the treatment of asthma, rhinitis, skin allergies, and anaphylaxis.
Tripelennamine
A histamine H1 antagonist with low sedative action but frequent gastrointestinal irritation. It is used to treat ASTHMA; HAY FEVER; URTICARIA; and RHINITIS; and also in veterinary applications. Tripelennamine is administered by various routes, including topically.
Bronchi
Anti-Allergic Agents
Muscle, Smooth
Unstriated and unstriped muscle, one of the muscles of the internal organs, blood vessels, hair follicles, etc. Contractile elements are elongated, usually spindle-shaped cells with centrally located nuclei. Smooth muscle fibers are bound together into sheets or bundles by reticular fibers and frequently elastic nets are also abundant. (From Stedman, 25th ed)
Airway Resistance
Bronchoconstriction
Narrowing of the caliber of the BRONCHI, physiologically or as a result of pharmacological intervention.
Trachea
The cartilaginous and membranous tube descending from the larynx and branching into the right and left main bronchi.
Enterochromaffin-like Cells
Neuroendocrine cells in the glands of the GASTRIC MUCOSA. They produce HISTAMINE and peptides such as CHROMOGRANINS. ECL cells respond to GASTRIN by releasing histamine which acts as a paracrine stimulator of the release of HYDROCHLORIC ACID from the GASTRIC PARIETAL CELLS.
Passive Cutaneous Anaphylaxis
An evanescent cutaneous reaction occurring when antibody is injected into a local area on the skin and antigen is subsequently injected intravenously along with a dye. The dye makes the rapidly occurring capillary dilatation and increased vascular permeability readily visible by leakage into the reaction site. PCA is a sensitive reaction for detecting very small quantities of antibodies and is also a method for studying the mechanisms of immediate hypersensitivity.
Gastrins
A family of gastrointestinal peptide hormones that excite the secretion of GASTRIC JUICE. They may also occur in the central nervous system where they are presumed to be neurotransmitters.
Serotonin
A biochemical messenger and regulator, synthesized from the essential amino acid L-TRYPTOPHAN. In humans it is found primarily in the central nervous system, gastrointestinal tract, and blood platelets. Serotonin mediates several important physiological functions including neurotransmission, gastrointestinal motility, hemostasis, and cardiovascular integrity. Multiple receptor families (RECEPTORS, SEROTONIN) explain the broad physiological actions and distribution of this biochemical mediator.
Mucuna
A plant genus of the family FABACEAE that is the source of mucuna gum.
Stomach
Muscle Contraction
A process leading to shortening and/or development of tension in muscle tissue. Muscle contraction occurs by a sliding filament mechanism whereby actin filaments slide inward among the myosin filaments.
Nasal Provocation Tests
Application of allergens to the nasal mucosa. Interpretation includes observation of nasal symptoms, rhinoscopy, and rhinomanometry. Nasal provocation tests are used in the diagnosis of nasal hypersensitivity, including RHINITIS, ALLERGIC, SEASONAL.
Capillary Permeability
The property of blood capillary ENDOTHELIUM that allows for the selective exchange of substances between the blood and surrounding tissues and through membranous barriers such as the BLOOD-AIR BARRIER; BLOOD-AQUEOUS BARRIER; BLOOD-BRAIN BARRIER; BLOOD-NERVE BARRIER; BLOOD-RETINAL BARRIER; and BLOOD-TESTIS BARRIER. Small lipid-soluble molecules such as carbon dioxide and oxygen move freely by diffusion. Water and water-soluble molecules cannot pass through the endothelial walls and are dependent on microscopic pores. These pores show narrow areas (TIGHT JUNCTIONS) which may limit large molecule movement.
Bronchial Spasm
Spasmodic contraction of the smooth muscle of the bronchi.
Bradykinin
A nonapeptide messenger that is enzymatically produced from KALLIDIN in the blood where it is a potent but short-lived agent of arteriolar dilation and increased capillary permeability. Bradykinin is also released from MAST CELLS during asthma attacks, from gut walls as a gastrointestinal vasodilator, from damaged tissues as a pain signal, and may be a neurotransmitter.
Imidazoles
Stimulation, Chemical
The increase in a measurable parameter of a PHYSIOLOGICAL PROCESS, including cellular, microbial, and plant; immunological, cardiovascular, respiratory, reproductive, urinary, digestive, neural, musculoskeletal, ocular, and skin physiological processes; or METABOLIC PROCESS, including enzymatic and other pharmacological processes, by a drug or other chemical.
Asthma
A form of bronchial disorder with three distinct components: airway hyper-responsiveness (RESPIRATORY HYPERSENSITIVITY), airway INFLAMMATION, and intermittent AIRWAY OBSTRUCTION. It is characterized by spasmodic contraction of airway smooth muscle, WHEEZING, and dyspnea (DYSPNEA, PAROXYSMAL).
Hypersensitivity
Gastric Fistula
Abnormal passage communicating with the STOMACH.
Parietal Cells, Gastric
Hypersensitivity, Immediate
Hypersensitivity reactions which occur within minutes of exposure to challenging antigen due to the release of histamine which follows the antigen-antibody reaction and causes smooth muscle contraction and increased vascular permeability.
Clemastine
Enterochromaffin Cells
Atropine
An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.