The effect of antiadrenaline compounds on acetylcholine responses of frog rectus abdominis muscle.

1. Nine antiadrenaline compounds and ergometrine have been examined for their effect on acetylcholine (ACh)-induced contractures of the frog isolated rectus abdominis muscle.2. Tolazoline caused potentiation (pP(2)=4.14 at 7 min). Slightly higher concentrations of tolazoline caused antagonism (pA(2)=3.68 at 37 min).3. No potentiation of ACh responses was seen with any of the remaining compounds, which all antagonized ACh responses. Phenoxybenzamine gave the highest, and ergometrine the lowest, pA(2) values.4. In the concentrations needed to determine pA(2), yohimbine and ergometrine also had other effects on the muscle.5. These results are discussed in the context of previous findings.