ABSTRACT
Background: Although traditional use of Tridax procumbens aqueous leaf extract (TPALE) in the management of respiratory disorders is documented, validated scientific evidence is scarce. Aim and Objectives: Trachea smooth muscle (TSM) relaxant activity of TPALE ingestion was investigated in the presence or absence of key TSM relaxant agents. This was with the aim at elucidating relaxant activity of TPALE on TSM. Materials and Methods: Contractile activity of TSM excised from TPALE treated (100 mg/kg) and non-treated rats was assessed pre - and post-incubation in salbutamol (10?4 M), theophylline (10?4 M), caffeine (10?4 M), naringin (10?4 M), and naringenin (10?4 M) using organ chamber connected to a force isometric transducer (Model 7004; Ugo-Basile VArese, Italy). Results: TPALE treatment significantly inhibited contractile activity in TSM. TPALE treated rats showed significantly inhibited contractile activity of the TSM pre (45.6%) and post-incubation (35%) in theophylline when compared to control pre (90.6%) and post-incubation (60%). Incubation of TSM from control and TPALE treated rats in salbutamol, significantly inhibited contractile activity (33.2%) and (37.2%), respectively. After incubation in caffeine, TSM from TPALE treated rats showed significant inhibition in the contractile activity (30.7%) as TSM from control postincubation (38.4%). TSM of TPALE-treated group pre-incubation showed significant inhibition in contractile activity (41.8%) when compared to the TSM of TPALE-treated Group (59.3%) and control (64.5%) post-incubation in naringin. However, incubation of TSM of TPALE-treated rats in naringenin significantly inhibited contractile activity (40.4%) when compared to pre-incubation (45%) and control pre - and post-incubation, respectively (52% and 90%). Conclusion: Calcium-activated K+ channels, ?2 adrenergic stimulation, and antioxidant activity contribute to the mediation of relaxant activity by TPALE in TSM.