M. Y. Winton

The effects of cholinergic substances upon the isolated heart of Periplaneta americana

Abstract The effects of acetylcholine and twelve other structurally related esters in accelerating the heartbeat rate of the isolated heart of Periplaneta americana were studied. Acetylcholine was about forty times more effective than acetylthiocholine or any other analogues studied, indicating that the receptor sites are much more stereospecific than the active site of insect cholinesterase. Organophosphorus and phenyl N-methylcarbamate anticholinesterase at great dilutions also accelerate the rate of heartbeat. The importance of the acetylcholine cholinesterase system at the insect neural synapses is emphasized by the protective action afforded by pyridine aldoxime methiodide and atropine sulphate in antagonizing the action of the anticholinesterases on heartbeat rate.