Myorelaxant Effects of the Essential Oil of Croton nepetaefolius on the Contractile Activity of the Guinea-Pig Tracheal Smooth Muscle

Abstract

The effects of the essential oil of Croton nepetaefolius (EOCN) on isolated guinea-pig trachea were investigated. EOCN decreased the preparation’s basal tone (EC₅₀ = 4.3 μg/mL) with a maximal effect similar to that of aminophylline. EOCN fully relaxed preparations pre-contracted with 60 mM K⁺ (IC₅₀ = 113.0 μg/mL). EOCN did not alter the E_m of smooth muscle cells in 5 and 80 mM K⁺. EOCN, at 300 and 600 μg/mL, reduced the contraction induced by ovalbumin (10 μg/mL) from 227.2 to 82.5 and 35.5 % of the 60 mM K⁺-induced contraction, respectively. EOCN blocked the submaximal contractions induced by histamine, carbachol and 60 mM K⁺ with a similar potency (IC₅₀ values = 123.9, 102.5 and 128.8 μg/mL, respectively). In conclusion, EOCN exerts respiratory smooth muscle antispasmodic activity by a mechanism that is probably myogenic and not specific for neurotransmitters and autacoids.

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