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Antispasmodic effects of the essential oil of Croton nepetaefolius on guinea‐pig ileum: a myogenic activity
Author(s) -
Magalhães Pedro Jorge Caldas,
Lahlou Saad,
LealCardoso José Henrique
Publication year - 2004
Publication title -
fundamental and clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.655
H-Index - 73
eISSN - 1472-8206
pISSN - 0767-3981
DOI - 10.1111/j.1472-8206.2004.00276.x
Subject(s) - contraction (grammar) , ileum , acetylcholine , chemistry , hexamethonium , tetrodotoxin , histamine , medicine , muscle contraction , endocrinology , nifedipine , guinea pig , biophysics , calcium , biochemistry , biology
The effects of essential oil of Croton nepetaefolius (EOCN) on guinea‐pig‐isolated ileum were studied. We previously demonstrated that EOCN induced reversible relaxation of ileal tone artificially increased by high [K + ] nutrient solution. This study aimed to elucidate whether these effects were caused by indirect, neural, or primarily by myogenic effect. EOCN (40 μ g/mL) induced a relaxation of basal tone corresponding to approximately 38% of the reference contraction (K + 60 m m ), and was unaltered by 0.5 m m hexamethonium, 0.5 μ m tetrodotoxin, 1 μ m indomethacin, and 100 μ m l ‐nitroarginine methyl ester ( l ‐NAME). Epinephrine‐ (100 μ m ) and EOCN‐induced maximal relaxation of ileum pre‐contracted with 60 m m KCl represented 16.8 ± 2.3% ( n = 10) and 95.0 ± 6.4% ( n = 6) of KCl‐induced contraction, respectively. EOCN (200 μ g/mL) had no effect on the transmembrane resting potential ( E m ) of ileum in nutrient solutions with normal (5 m m ) and high (80 m m ) [K + ]. EOCN similarly inhibited the contractions induced by KCl, acetylcholine (ACh) and histamine (IC 50 values of approximately 18, 28 and 21 μ g/mL, respectively). EOCN also inhibited both the nifedipine‐insensitive component of ACh‐induced contraction and the contraction induced by ACh in Ca 2+ ‐free solution. EOCN accelerated the reversal of a KCl‐induced tonic contraction upon withdrawal of Ca 2+ from the extracellular medium. Our results suggest that EOCN induces relaxation of guinea‐pig ileum by a direct action on smooth muscle via a mechanism largely independent of alterations of E m and Ca 2+ influx, possibly at the level of the contractile apparatus.