| Abstract: | The authors studied the influence of adrenaline-like substances and acetylcholine on the protoplasmic streaming in Physarella oblonga, investigating the effect on the duration of the rhythmic period. Adrenaline and noradrenaline proved to cause a shortening, whereas acetylcholine appeared to be capable of causing an extension of the period duration. The authors present and discuss critically the possibility that the adrenergic and cholinergic transmitter substances, which influence the visceral (mechano-) effectors in the higher animal organism often antagonistically, may also affect an elementary “functional” effector system responsible for protoplasmic streaming, and that in so doing they have comparable effects. The results of experiments with eserine, acetylcholine and a mixture of these two substances render it probable that an acetylcholine esterase and acetylcholine occur in the plasmodium. The mean normal value of the period duration was, calculated from 976 measurements and expressed in seconds: 284.183 ± 1.486 (S.E. of the mean). The average duration of the progressive and the regressive phase was found to be almost the same. |
