The effects of three benzodiazepines and of meprobamate on the action of smooth muscle stimulants on the guinea-pig ileum.

The benzodiazepines chlorodiazepoxide, diazepam and flurazepam and meprobamate depress the response of the guinea-pig ileum to acetylcholine, histamine and 5-hydroxytryptamine. As compared to the benzodiazepines the action of meprobamate is very weak. Chlorodiazepoxide has a weaker anti-acetylcholine activity than diazepam and flurazepam. On the other hand chlorodiazepoxide possesses a realtively strong anti-histamine activity. The three benzodiazeptines tested are about equally effective in reducing the contraction of the guinea-pig ileum caused by 5-hydroxytryptamine. The potency of diazepam and flurazepam in blocking the effect of the three smooth muscle stimulants appears to be rather similar.