The Action of Rotenone and Tetraethyl Pyrophosphate on the isolated Heart of the Cockroach

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Abstract
A method based upon Yeager's technique is described permitting the study of the surviving heart ofPeriplaneta americanaunder varying conditions for several hours.Rotenone causes diastolic contractions, decrease of frequency and cessation in diastole, threshold action on the neurogenic automatic cardiac centre.The latent period of the rotenone action is dependent upon the concentration. Using this principle a method is developed for quantitative estimation of the activity of derris preparations.Tetraethyl pyrophosphate has a strongly accelerating action on the frequency of the heart and increases the amplitude; in this case there is no latent period. Threshold 0·000008 per cent. Presumably TEPP activates the neurogenic heart automatism by its vigorous anticholinesterase activity.

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