Shin_1993_Life.Sci_53_1495

The effects of berberine on guinea-pig ileum contractility were studied in both transmurally-stimulated and unstimulated preparations. Transmural stimulation (80 V, 0.5 ms, 0.05 Hz) of the guinea-pig ileal segments produced a twitch response. Berberine (10(-8)-10(-5) M) enhanced this response dose-dependently. Atropine (10(-7) M), but not mecamylamine (10(-5) M), abolished this response. Acetylcholine (3 x 10(-9) and 10(-8) M) also enhanced the response to transmural stimulation. Pretreatment with hemicholinium (3 x 10(-5) M) antagonized the effect of berberine but failed to change that of acetylcholine. Berberine (10(-5) M) also antagonized the alpha 2-adrenoceptor agonist xylazine (10(-8) and 10(-7) M)-induced inhibition of the twitch response to transmural stimulation. In unstimulated ileal preparations, berberine (10(-5) M) produced contractile responses. In these preparations, atropine (10(-6) M), but not mecamylamine (10(-4) M), abolished the response to berberine. Furthermore, berberine (10(-6)-10(-4) M) inhibited dose-dependently the cholinesterase activity of the guinea-pig blood. The results suggest that berberine increases ileal contractility by: 1) increasing acetylcholine release from the postganglionic parasympathetic nerve terminal, 2) increasing acetylcholine retention through an inhibition of cholinesterase activity, and 3) blocking alpha 2-adrenoceptors, possibly in the postganglionic parasympathetic nerve.