Abstract

ABAD SANTOS, F; NOVALBOS, J; GALLEGO SANDIN, S  and  GALVEZ MUGICA, Mª A. Regulation of bronchial tone in chronic obstructive pulmonary disease (COPD): role of muscarinic receptors. An. Med. Interna (Madrid) [online]. 2003, vol.20, n.4, pp.45-49. ISSN 0212-7199.

Anticholinergic agents have proved to be of particular value in the treatment of COPD, as vagal cholinergic tone appears to be the only reversible component of airway narrowing, opposite to what happens in asthma. Anticholinergics block muscarinic receptors on airway smooth muscle an submucosal gland cells. Three subtypes of muscarinic receptors have been demonstrated in human airways. M₁ receptors in parasympathectic ganglia facilitate cholinergic neurotransmision. M₃ receptors on airway smooth muscle cells and glands mediate bronchoconstriction and mucus secretion. M₂ receptors at cholinergic nerve endings inhibit the release of acetylcholine and therefore act as feedback inhibitory receptors (autoreceptors). Ipratropium bromide is a non-selective muscarinic antagonist and therefore blocks M₁, M₂ and M₃ receptors. Tiotropium is a novel, potent, and long-lasting muscarinic antagonist that has a kinetic selectivity for M₁ and M₃ receptors because it dissociated very quickly from M₂ receptors. Once-daily inhaled tiotropium is a safe and effective bronchodilator useful as a first-line maintenance therapy in COPD.

Keywords : COPD; Muscarinic receptors; Ipratropium; Tiotropium.

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