Paramecium - A modell system for studying cellular graviperception

Abstract

Experiments under varied gravitational accelerations as well as in density-adjusted media showed that sensation of gravity in protists may clear gravi- responses (gravitaxis and gravikinesis) is an ideal model system to prove this hypothesis since the ciliary activity and thus the swimming behaviour is controlled by the membrane potential. It has also been assumed that the cytoplasmic mass causes a distinct stimulation of the bipolarly distributed mechano-sensitive K and Ca ion channels in the plasma membrane in dependence of the spatial orien- tation of the cell. In order to prove this hypo- thesis, different channel blockers are currently under investigation. Gadolinium did not inhibit gravitaxis in Paramecium, showing that it does not specifically block gravireceptors. Further studies concentrated on the question of whether second messengers are involved in the gravity signal trans- duction chain. Exposure to 5g for up to 10 min led to a significant increase in cAMP.