Which of the following was previously used to diagnose bronchial asthma
Oxtremorine
Methacoline
Carbachol
Oxybutynin
Methacholine normally acts on M2 receptor present on heart. "Methacholine challenge test" was used to diagnose bronchial asthma, where it can cause bronchoconstriction because of increased sensitivity of M3 receptors due to airway hyperreactivity.