INSP(3)-MODULATED PHOTOPHOBIC RESPONSES IN BLEPHARISMA

Cells of Blepharisma japonicum are characterized by a light avoiding r eaction, the step-up photophobic response. Microscope videorecording a nd behavioral analysis showed that photosensitivity of these cells is greatly reduced when they were incubated in solutions containing such agents as neomycin, an inhibitor of phospholipase C, heparin, a inhibi tor of inositol receptors and Li+ ions, potent inhibitor of monophosph oinositol phosphatase, which are known to modify the cell inositol lip id pathway. All of these substances caused a decrease of the number of cells reacting to light stimulation with photophobic responses, and l atency of the cell responses were appreciably extended. The observed i nhibitory effects in all tested cases were dependent on both the time of cell incubation and doses of neomycin, heparin or Li+ ions used. Th e obtained behavioral results allow to suggest that in protozoan Bleph arisma there exists possibly InsP(3) pathway which seems to be one of the mechanisms of signal transduction.