Structural aspects of the effect of ethyl benzoates on caffeine contracture

The effect of ethyl benzoate, ethyl o- and p-fluorobenzoate and ethyl o- and p-toluate on the caffeine-induced contracture of frog sartorius muscle was investigated. All drugs with the exception of ethyl o-toluate depressed caffeine-induced contractures. It is proposed that the methyl group in ethyl o-toluate sterically blocks the ester carbonyl group from exerting its inhibitory action. It is further proposed that ethyl o-aminobenzoate exerts its potentiating effect through the lone pair of electrons on the nitrogen atom.