Methacholine chloride is a potent muscarinic receptor agonist[1]. Methacholine chloride acts directly on acetylcholine receptors on smooth muscle, resulting in bronchoconstriction and airway narrowing[2, 3]. Methacholine chloride can be used to measure airway hyperresponsiveness (AHR) as a diagnostic aid in evaluating individuals with asthma-like symptoms and normal resting expiratory flow rates[4, 5].
In vivo, Methacholine chloride (0.5mg/kg) induced bronchoconstriction in male Balb c mice by intravenous injection[6].
References:
[1] Kumar S, Singh J, Kedika R, et al. Role of muscarinic-3 receptor antibody in systemic sclerosis: correlation with disease duration and effects of IVIG[J]. American Journal of Physiology-Gastrointestinal and Liver Physiology, 2016, 310(11): G1052-G1060.
[2] Kistemaker L E M, Gosens R. Acetylcholine beyond bronchoconstriction: roles in inflammation and remodeling[J]. Trends in pharmacological sciences, 2015, 36(3): 164-171.
[3] Wagner E M, Jacoby D B. Methacholine causes reflex bronchoconstriction[J]. Journal of applied physiology, 1999, 86(1): 294-297.
[4] Hallstrand T S, Leuppi J D, Joos G, et al. ERS technical standard on bronchial challenge testing: pathophysiology and methodology of indirect airway challenge testing[J]. European Respiratory Journal, 2018, 52(5).
[6] Choi S H, Sheen Y H, Kim M A, et al. Clinical implications of oscillatory lung function during methacholine bronchoprovocation testing of preschool children[J]. BioMed Research International, 2017, 2017(1): 9460190.