Related Experiment Video
Updated: Aug 26, 2026

A Reversible, Non-invasive Method for Airway Resistance Measurements and Bronchoalveolar Lavage Fluid Sampling in Mice
Published on: April 13, 2010
Interaction with histamine H1-receptors and bronchospasmolytic effects of urapidil
Abstract:
The antihypertensive drug, urapidil, competitively antagonized the histamine-induced contractions in guinea pig isolated tracheal and ileal preparations. Its affinity to histamine H1-receptors was 3-fold higher than that of histamine but 10- and 30-fold weaker than that of diphenhydramine and indoramin, respectively. Urapidil did not inhibit contractions induced by muscarinic agonists in both organs. Investigations in spontaneously breathing guinea pigs showed a greater efficacy of urapidil than that of diphenhydramine in protecting the animals against histamine-induced bronchospasms, whereas acetylcholine-induced spasms were only moderately inhibited. Theophylline, at a 100-fold higher dosage than urapidil, protected the animals against both histamine and acetylcholine challenges. This experimentally observed effect of urapidil supports clinical trials in hypertensive patients suffering also from obstructive lung disease and/or allergic illness.
Related Concept Videos
Drugs Used in Lower Respiratory Disorders: Overview
Bronchodilators, the first step of respiration enhancement, come in various forms, each with its own mechanism...
Upper Respiratory Drugs: Antitussives, Expectorants, and Mucolytics
Antitussives include codeine, dextromethorphan (Robitussin), and benzonatate (Tessalon). Codeine and dextromethorphan exert their effects centrally by suppressing the cough reflex center in the medulla. Benzonatate operates peripherally within the respiratory tract by anesthetizing...
Antiasthma Drugs: β2-Adrenoceptor Agonists
One class of bronchodilators includes β2-adrenoceptor agonists. These agents target the β2-adrenoceptors located on bronchial smooth muscle cells. By stimulating these receptors, β2-agonists induce relaxation in these...
Antiasthma Drugs: Methylxanthines
Theophylline is thought to inhibit phosphodiesterase enzymes, increasing intracellular levels of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). This rise in cAMP and cGMP concentrations stimulates cardiac function,...
Antiasthma Drugs: Muscarinic Receptor Antagonists
Antimuscarinic agents compete with ACh for the same binding site on the muscarinic receptors. By binding to these receptors, they inhibit the downstream effects of ACh and block the parasympathetic...
Antiasthma Drugs: Mast Cell Stabilizers and Anti-IgE Drugs
Mast cell stabilizers, such as cromolyn (also known as sodium cromoglycate) and nedocromil (Tilade), are effective drugs in asthma management. These stabilizers hinder histamine release by skillfully obstructing the activation of mast cells and other cellular entities. Notably, they navigate this task without...

