Relaxant effects of the essential oil of Mentha pulegium L. in rat isolated trachea and urinary bladder

• Published in: Journal of pharmacy and pharmacology 2012-12, Vol.64 (12), p.1777-1784
• Main Authors: Soares, Pedro Marcos Gomes, de Freitas Pires, Alana, de Souza, Emmanuel Prata, Assreuy, Ana Maria Sampaio, Criddle, David Neil
• Format: Article
• Language: English
• Subjects: Acetylcholine; Animals; bladder; Calcium Chloride - metabolism; contraction; Dose-Response Relationship, Drug; Inhibitory Concentration 50; Male; Mentha pulegium - chemistry; Mentha pulegium essential oil; Monoterpenes - pharmacology; Muscle Contraction - drug effects; Muscle, Smooth - drug effects; Muscle, Smooth - physiology; Oils, Volatile - pharmacology; Parasympatholytics - pharmacology; Plant Extracts - pharmacology; Potassium Chloride; pulegone; Rats; Rats, Wistar; trachea; Trachea - drug effects; Trachea - physiology; Urinary Bladder - drug effects; Urinary Bladder - physiology
• ISSN: 0022-3573; 2042-7158
• DOI: 10.1111/j.2042-7158.2012.01558.x

Objectives  We evaluated the relaxant activity of the essential oil of Mentha pulegium L. (EOMP) and pulegone in rat isolated tracheal and bladder smooth muscles. Methods  Isometric contractions of isolated tracheal and bladder strips from male Wistar rats were induced by KCl (K60; 60 mm) or acetylcholine (ACh; 10 µm). EOMP and its majory compound pulegone were incubated, after contracting agent, with the tissues in cumulating concentrations. Key findings  EOMP (3–300 µg/ml) inhibited the contractions induced by ACh and K60 in both tissues, but was more effective against the contractions induced by K60 in trachea (IC50 = 40.47 ± 3.27 µg/ml) compared with ACh. Its relaxant action rules out ganglia and NO participation. Pulegone (10−7 to 10−3 m) inhibited the contractions induced by ACh and K60 in both tissues. EOMP concentration‐dependently inhibited the contractions evoked by addition of CaCl2 in depolarised trachea, suggesting inhibition of extracellular calcium entry. Conclusions  These findings suggests that EOMP induced relaxant responses in pre‐contracted smooth muscles of rat trachea and bladder, which are likely to be mediated via inhibition of calcium entry, mainly by its major compound, pulegone. These effects are coherent with the popular use of EOMP as an antispasmodic agent.