BRL37344 (100 μM) significantly decreases the amplitude of the electrical field stimulation (EFS)-induced contractions of guinea pig DSM isolated strips in the absence or presence of SR59230A (10 μM). Original recordings illustrating EFS-induced (0.5–50 Hz) contractions of DSM isolated strips in response to 100 μM BRL37344 (A), 10 μM SR59230A and 100 μM BRL37344 combined (C), and 10 μM SR59230A (E). Frequency-response curves for the EFS-induced (0.5–50 Hz) contractions in response to 100 μM BRL37344 (B), 10 μM SR59230A and 100 μM BRL37344 combined (D), 10 μM SR59230A (F; n = 10, N = 4 for B; n = 11, N = 5 for D; n = 9, N = 6, P > 0.05 for F; *P < 0.05, **P < 0.01, ***P < 0.005). EFS-induced contraction amplitude at 50 Hz under control conditions was taken to be 100%.