Methacholine Chloride: A quaternary ammonium parasympathomimetic agent with the muscarinic actions of ACETYLCHOLINE. It is hydrolyzed by ACETYLCHOLINESTERASE at a considerably slower rate than ACETYLCHOLINE and is more resistant to hydrolysis by nonspecific CHOLINESTERASES so that its actions are more prolonged. It is used as a parasympathomimetic bronchoconstrictor agent and as a diagnostic aid for bronchial asthma. (From Martindale, The Extra Pharmacopoeia, 30th ed, p1116)Bronchoconstrictor Agents: Agents causing the narrowing of the lumen of a bronchus or bronchiole.Drug Storage: The process of keeping pharmaceutical products in an appropriate location.Methacholine Compounds: A group of compounds that are derivatives of beta-methylacetylcholine (methacholine).Drug Stability: The chemical and physical integrity of a pharmaceutical product.Chlorides: Inorganic compounds derived from hydrochloric acid that contain the Cl- ion.Bronchial Provocation Tests: Tests involving inhalation of allergens (nebulized or in dust form), nebulized pharmacologically active solutions (e.g., histamine, methacholine), or control solutions, followed by assessment of respiratory function. These tests are used in the diagnosis of asthma.Bronchial Hyperreactivity: Tendency of the smooth muscle of the tracheobronchial tree to contract more intensely in response to a given stimulus than it does in the response seen in normal individuals. This condition is present in virtually all symptomatic patients with asthma. The most prominent manifestation of this smooth muscle contraction is a decrease in airway caliber that can be readily measured in the pulmonary function laboratory.Bronchoconstriction: Narrowing of the caliber of the BRONCHI, physiologically or as a result of pharmacological intervention.Chloride Channels: Cell membrane glycoproteins that form channels to selectively pass chloride ions. Nonselective blockers include FENAMATES; ETHACRYNIC ACID; and TAMOXIFEN.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).Forced Expiratory Volume: Measure of the maximum amount of air that can be expelled in a given number of seconds during a FORCED VITAL CAPACITY determination . It is usually given as FEV followed by a subscript indicating the number of seconds over which the measurement is made, although it is sometimes given as a percentage of forced vital capacity.Airway Resistance: Physiologically, the opposition to flow of air caused by the forces of friction. As a part of pulmonary function testing, it is the ratio of driving pressure to the rate of air flow.Bronchi: The larger air passages of the lungs arising from the terminal bifurcation of the TRACHEA. They include the largest two primary bronchi which branch out into secondary bronchi, and tertiary bronchi which extend into BRONCHIOLES and PULMONARY ALVEOLI.Vinyl Chloride: A gas that has been used as an aerosol propellant and is the starting material for polyvinyl resins. Toxicity studies have shown various adverse effects, particularly the occurrence of liver neoplasms.Respiratory Hypersensitivity: A form of hypersensitivity affecting the respiratory tract. It includes ASTHMA and RHINITIS, ALLERGIC, SEASONAL.Administration, Inhalation: The administration of drugs by the respiratory route. It includes insufflation into the respiratory tract.Sodium Chloride: A ubiquitous sodium salt that is commonly used to season food.Parasympathomimetics: Drugs that mimic the effects of parasympathetic nervous system activity. Included here are drugs that directly stimulate muscarinic receptors and drugs that potentiate cholinergic activity, usually by slowing the breakdown of acetylcholine (CHOLINESTERASE INHIBITORS). Drugs that stimulate both sympathetic and parasympathetic postganglionic neurons (GANGLIONIC STIMULANTS) are not included here.Acetylcholinesterase: An enzyme that catalyzes the hydrolysis of ACETYLCHOLINE to CHOLINE and acetate. In the CNS, this enzyme plays a role in the function of peripheral neuromuscular junctions. EC 3.1.1.7.Pregnancy Tests: Tests to determine whether or not an individual is pregnant.Bronchodilator Agents: Agents that cause an increase in the expansion of a bronchus or bronchial tubes.Ethanolamines: AMINO ALCOHOLS containing the ETHANOLAMINE; (-NH2CH2CHOH) group and its derivatives.Cough: A sudden, audible expulsion of air from the lungs through a partially closed glottis, preceded by inhalation. It is a protective response that serves to clear the trachea, bronchi, and/or lungs of irritants and secretions, or to prevent aspiration of foreign materials into the lungs.Mannitol: A diuretic and renal diagnostic aid related to sorbitol. It has little significant energy value as it is largely eliminated from the body before any metabolism can take place. It can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function and has been used for determination of glomerular filtration rate. Mannitol is also commonly used as a research tool in cell biological studies, usually to control osmolarity.Antitussive Agents: Agents that suppress cough. They act centrally on the medullary cough center. EXPECTORANTS, also used in the treatment of cough, act locally.Dose-Response Relationship, Drug: The relationship between the dose of an administered drug and the response of the organism to the drug.Drug Monitoring: The process of observing, recording, or detecting the effects of a chemical substance administered to an individual therapeutically or diagnostically.Universal Precautions: Prudent standard preventive measures to be taken by professional and other health personnel in contact with persons afflicted with a communicable disease, to avoid contracting the disease by contagion or infection. Precautions are especially applicable in the diagnosis and care of AIDS patients.Pharmaceutical Preparations: Drugs intended for human or veterinary use, presented in their finished dosage form. Included here are materials used in the preparation and/or formulation of the finished dosage form.Laboratories: Facilities equipped to carry out investigative procedures.Laboratories, Hospital: Hospital facilities equipped to carry out investigative procedures.Clinical Laboratory Techniques: Techniques used to carry out clinical investigative procedures in the diagnosis and therapy of disease.Animals, LaboratoryMedical Laboratory Personnel: Health care professionals, technicians, and assistants staffing LABORATORIES in research or health care facilities.Molecular Sequence Data: Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.Adenosine: A nucleoside that is composed of ADENINE and D-RIBOSE. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter.Adenosine Monophosphate: Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2'-, 3'-, or 5'-position.Adenine NucleotidesCyclic AMP: An adenine nucleotide containing one phosphate group which is esterified to both the 3'- and 5'-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and ACTH.Receptor, Adenosine A2A: A subclass of adenosine A2 receptors found in LEUKOCYTES, the SPLEEN, the THYMUS and a variety of other tissues. It is generally considered to be a receptor for ADENOSINE that couples to the GS, STIMULATORY G-PROTEIN.Receptor, Adenosine A1: A subtype of ADENOSINE RECEPTOR that is found expressed in a variety of tissues including the BRAIN and DORSAL HORN NEURONS. The receptor is generally considered to be coupled to the GI, INHIBITORY G-PROTEIN which causes down regulation of CYCLIC AMP.Adenosine Deaminase: An enzyme that catalyzes the hydrolysis of ADENOSINE to INOSINE with the elimination of AMMONIA.Atropine: An alkaloid, originally from Atropa belladonna, but found in other plants, mainly SOLANACEAE. Hyoscyamine is the 3(S)-endo isomer of atropine.Lung: Either of the pair of organs occupying the cavity of the thorax that effect the aeration of the blood.Pirenzepine: An antimuscarinic agent that inhibits gastric secretion at lower doses than are required to affect gastrointestinal motility, salivary, central nervous system, cardiovascular, ocular, and urinary function. It promotes the healing of duodenal ulcers and due to its cytoprotective action is beneficial in the prevention of duodenal ulcer recurrence. It also potentiates the effect of other antiulcer agents such as CIMETIDINE and RANITIDINE. It is generally well tolerated by patients.Muscarinic Antagonists: Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system.Alligators and Crocodiles: Large, long-tailed reptiles, including caimans, of the order Loricata.Salt Gland: A compound tubular gland, located around the eyes and nasal passages in marine animals and birds, the physiology of which figures in water-electrolyte balance. The Pekin duck serves as a common research animal in salt gland studies. A rectal gland or rectal salt gland in the dogfish shark is attached at the junction of the intestine and cloaca and aids the kidneys in removing excess salts from the blood. (Storer, Usinger, Stebbins & Nybakken: General Zoology, 6th ed, p658)Biology: One of the BIOLOGICAL SCIENCE DISCIPLINES concerned with the origin, structure, development, growth, function, genetics, and reproduction of animals, plants, and microorganisms.Osmosis: Tendency of fluids (e.g., water) to move from the less concentrated to the more concentrated side of a semipermeable membrane.Neuronal Plasticity: The capacity of the NERVOUS SYSTEM to change its reactivity as the result of successive activations.Genes, mos: Retrovirus-associated DNA sequences (mos) originally isolated from the Moloney murine sarcoma virus (Mo-MSV). The proto-oncogene mos (c-mos) codes for a protein which is a member of the serine kinase family. There is no evidence as yet that human c-mos can become transformed or has a role in human cancer. However, in mice, activation can occur when the retrovirus-like intracisternal A-particle inserts itself near the c-mos sequence. The human c-mos gene is located at 8q22 on the long arm of chromosome 8.Reptiles: Cold-blooded, air-breathing VERTEBRATES belonging to the class Reptilia, usually covered with external scales or bony plates.