Effects of methylflavonolamine hydrochloride on contractility of isolated rabbit ileum

Methylflavonolamine hydrochloride (MFA), verapamil (Ver), and trifluoperazine (Tri) inhibited the contractions induced by submaximal concentrations of acetylcholine (ACh) and serotonin (5-HT). IC50 values (mumol.L-1) were 33.2 +/- 0.7, 0.276 +/- 0.018, 3.83 +/- 0.23, and 15.31 +/- 0.10, 0.233 +/- 0.017, 2.33 +/- 0.20, respectively. MFA, Ver, and Tri inhibited the contractions induced by CaCl2 and pD'2 values were 4.3 +/- 0.3, 6.23 +/- 0.22, 4.99 +/- 0.24, respectively. MFA 3 mumol.L-1, Ver 0.03 mumol.L-1, and Tri 3 mumol.L-1 inhibited the contractions induced by ACh in Ca(2+)-free medium, while MFA 60 mumol.L-1, Tri 30 mumol.L-1, but not Ver 0.6 mumol.L-1, had pronounced inhibitions on extracellular calcium-dependent contractions induced by ACh. These results suggest that MFA has a calcium antagonistic effect and that MFA is similar to Tri, but not Ver, in mechanism.