Studies on the antispasmodic and cardiovascular activities of methanolic crude extract of Andropogon muricatus. Nash

Andropogon muricatus Nash., has been used in the traditional medicine as an antispasmodic and in palpitation and this study was aimed to provide scientific basis for its use in gastrointestinal and cardiovascular disorders. Apporaximatly 2 cm long segments of rabbit jejunum and 2-3 mm wide aortic rings and strips of guinea-pig atria were incubated in normal Tyrod’s and Krab’s solutions at 37°C and 32°C respectively, aerated with carbogen. Responses were measured on Bioscience oscillograph. Blood pressure was recorded via the cannula inserted into the carotid artery in anesthetized rat coupled with Gross model 79 Polygraph. In rabbit jejunum it caused inhibition of spontaneous and high K+ (80 mM)-induced contractions at 0.01-0.30 mg/mL in both cases, with EC50 values of 0.08±0.03 and 0.086±0.03 mg/mL, respectively, which is suggestive of calcium channel blocking (CCB) activity. The CCB activity was confirmed when it shifted the Ca++ dose-response curves to the right at similar dose range. In anaesthetized rats, it caused a fall in mean arterial blood pressure. The effect was dose-dependent; fall in BP was 14.5%±1.22%, 48.0%±2.10%, and 65.0%±0.73% at 10, 30 and 100 mg/Kg respectively. In isolated rabbit aorta it caused inhibition of phenylephrine (1 µM) and high K+ (80 mM) induced contractions at 0.1-1.0 and 0.01-0.30 mg/mL, with EC50 values of 0.43±0.086 and 0.082±0.038 mg/mL respectively, indicative of nonspecific vasodilatation. In guinea-pig atria it suppressed the rate and force of spontaneous contractions at 0.03-5.0 and 0.10-5.0 mg/mL with EC50 values of 1.38±0.19 and 1.32±0.19 mg/mL respectively. These results suggest that the antispasmodic and cardiovascular effects of Andropogon muricatus are mediated though CCB, and this study provides mechanistic base for some of its traditional uses.