Search results for "histamine"

Models with clinically-relevant and life-threatening histamine-related cardiovascular disturbances: Evaluation of the clinical effectiveness of H1/H2…

1996

Effect of dantrolene sodium in isolated guinea-pig trachea.

1990

The effect of dantrolene sodium (3 microM-0.3 mM) on the spontaneous tone and responses to various contractile agonists was studied in isolated guinea-pig trachea. Dantrolene produced a concentration-related inhibition of the spontaneous tracheal tone, reaching a value of 94.8 +/- 4.8% of the relaxation induced by caffeine 10 mM. Removal of the epithelium did not affect the dantrolene-induced relaxation. Dantrolene did not alter the concentration-response curve for KCl and produced only small displacements of the concentration-response curves for CaCl2, acetylcholine and histamine, without affecting their maximal effects. Dantrolene dose relatedly inhibited the contraction induced by caffei…

EFFECTS OF CROMAKALIM (BRL-34915) IN TRACHEA ISOLATED FROM ACTIVELY SENSITIZED GUINEA-PIGS

1993

Abstract The effects of cromakalim were examined in tracheal strips isolated from normal (unsensitized) guinea-pigs and from animals actively sensitized to bovine serum albumin. Sensitized tracheae exhibited hyper-responsiveness to KCl, acetylcholine and histamine. In normal and sensitized tracheae, cromakalim (0·01–10 μm) produced a concentration-related suppression of spontaneous tone. The ability of cromakalim to relax tracheal strips was reduced when tone was raised by KCl (25 Mm), acetylcholine (0·1 Mm) or histamine (0·1 Mm) and lost against KCl (120 Mm)-induced spasm. Procaine (5 Mm) abolished the relaxant effect of cromakalim whilst tetraethylammonium (8 Mm) was without effect. These…

Role of epithelium in agonist-induced contractile responses of guinea-pig trachealis: influence of the surface through which drug enters the tissue.

1990

1. A method has been used in guinea-pig isolated tracheal rings to achieve selective drug entry from the adventitial or mucosal surface. A study has been made of the effects of epithelium removal on responses to spasmogens entering the tissue solely from the adventitial or the mucosal surface. 2. Cumulative concentration-response curves for KCl (1 to 100 mM), acetylcholine (0.1 microM to 10 mM) and histamine (1 microM to 1 mM) were constructed in intact and epithelium-denuded tracheal rings in circumstances where drug entry was unrestricted or restricted to the adventitial or mucosal surface. 3. Epithelium removal did not alter the responsiveness or sensitivity of tracheal rings to KCl eith…

Histamine binding to H2 receptors stimulates phospholipid methylation in mast cells

1982

Rat peritoneal mast cells incubated in vitro in the presence of L-[methyl-3H] methionine and exposed to histamine undergo a rapid but transient increase in phospholipid methylation. By using specific H1- and H2-receptor antagonists, and histamine analogues differing in their H2-receptor agonist potency, it has been demonstrated that this metabolic event is dependent on histamine binding to H2-receptors.

Mediator-Induced Changes in Macromolecular Permeability in the Rat Mesenteric Microcirculation

1995

An intravital fluorescence microscopic method for measurement of changes in macromolecular permeability has been established in the mesenterial microcirculation of the rat. After exteriorization of the fat-free distal part of the ileal mesentery, a 1-hr period of stabilization was followed by the injection of FITC-labeled macromolecules. Five minutes later, histamine, leukotriene B4, or leukotriene C4 was topically applied to the tissue by means of a micromanipulator. Areas of 1 mm2 were videotaped with a SIT camera. The fluorescence intensity of these areas was measured by an analogous video image processing system and displayed as gray value histograms. The shift of the frequency of gray …

Pharmacological activity of PF-904 in guinea pig in vivo, and on human bronchus and neutrophils in vitro.

1997

The effects of PF-904 (4-amino-1-ethyl-6-methylpyrazino[2,3-c][1,2,6]thiadiazine 2,2-dioxide), a pyrazinothiadiazine derivative, were examined in guinea-pig airways in vivo, in human isolated bronchus and human polymorphonuclear leukocytes. PF-904 (12.5-200 mg/kg, intraduodenal) reduced bronchoconstriction in response to histamine, arachidonic acid, platelet-activating factor (PAF) and methacholine. PF-904 (50-200 mg/kg) prevented PAF-induced airways hyperreactivity and inhibited antigen-induced bronchoconstriction, airway microvascular leakage and eosinophil lung accumulation, but antigen-induced airways hyperresponsiveness was not reduced. PF-904 (1 microM-1 mM) produced complete inhibiti…

Comparative relaxant effects of the NO donors sodium nitroprusside, DEA/NO and SPER/NO in rabbit carotid arteries.

1999

1. Sodium nitroprusside (SNP, 10(-9)-3x10(-4) M), diethylamine/NO complex (DEA/NO, 10(-9)-10(-4) M) and spermine/NO complex (SPER/NO, 10(-8)-3x10(-4) M) induced concentration-dependent relaxation of isolated rabbit carotid arteries precontracted with KCl (50 mM) or with histamine (3x10(-6) M). 2. In KCl-precontracted arteries the order of potency was SNP=DEA/NO>SPER/NO, and in histamine-precontracted arteries the order of potency was SNP>DEA/NO>SPER/NO. Relaxations to the three NO donors were significantly higher in histamine-precontracted arteries than in KCl-precontracted arteries. 3. The guanylyl cyclase inhibitor methylene blue (10(-5) M) significantly inhibited relaxations to the three…

Antiasthmatic Effects of <i>Galphimia glauca</i>, Gallic Acid, and Related Compounds Prevent Allergen- and Platelet-Activating Factor-Ind…

1992

A methanolic extract from Galphimia glauca (320 mg/kg, orally) inhibited acute bronchial reactions to allergen (ovalbumin, 10 mg/ml) and platelet-activating factor (PAF, 1 microgram/ml) inhalation challenges, but not to histamine or acetylcholine in spontaneously breathing guinea pigs. Furthermore, the PAF-induced bronchial hyperreactivity was markedly reduced. Gallic acid and related compounds as well as the flavonoid, quercetin, were identified as active compounds. Gallic acid, methyl gallate and quercetin showed significant effects after a single oral dose of 45 mg/kg, tetragalloyl quinic acid after 5 mg/kg. Continuous treatment of the animals with one certain fraction (GG II, 3 days, 3 …

Epithelium modulates the reactivity of sensitized guinea-pig trachea: influence of the surface of drug entry.

1991

Abstract A technique by which drug access was restricted to either the mucosal or the adventitial surface of tracheal rings isolated from sensitized guinea-pigs was applied to study the role of the epithelium in modulating responses to KCl, acetylcholine, histamine and antigen (bovine serum albumin, BSA). Epithelium removal did not alter the responsiveness or sensitivity of tracheal rings to KCl. In contrast, a leftward shift occurred for concentration-response curves to acetylcholine (concentration ratio (CR) = 4·1), histamine (CR = 2·9) and BSA (CR = 33·9) entering from the mucosal surface of de-epithelialized trachea. This shift was not associated with changes in the maximal effect of th…