A potent, structurally specific stimulant action of procaine in bullfrog lung

1. Local anesthetics with a procaine-like structure are exceptionally potent smooth muscle stimulation in Rana catesbeiana. 2. Procaine completely reverses the relaxant effect of 1 mM theophylline, an action that cannot be duplicated with carbachol, histamine or 5-hydroxytryptamine. 3. Stimulant activity is related to the procaine-like structure rather than local anesthetic potency, and is independent of pH between 7.0 and 8.4. 4. The high potency and structural specificity of this effect suggests an action at a specific receptor site rather than a diffuse action on membrane structure.