Application of a single concentration of BRL37344 (100 μM) decreased the guinea pig DSM spontaneous phasic contraction amplitude, muscle force integral, and phasic contraction frequency in the absence of atropine. A, C: original recording of DSM contractions illustrating BRL37344 inhibitory effect in the absence (A) or presence of 1 μM atropine (C). B, D: summary data showing BRL37344 (100 μM) inhibitory effect in the absence (B; n = 14, N = 5, ***P < 0.005) or presence of 1 μM atropine (D; n = 9, N = 5, ***P < 0.005). Spontaneous contractions were taken to be 100%. TTX (1 μM) was present throughout the experiments.