A Videomicroscopic Study of the Effect of L-cis -Diltiazem on the Photobehavior of Stentor Coeruleus

• Published in: Photochemistry and photobiology Vol. 77; no. 3; pp. 339 - 342
• Main Authors: Walerczyk, M, Fabczak, H, Fabczak, S
• Format: Journal Article
• Language: English
• Published: 01.03.2003
• Subjects: Stentor coeruleus
• ISSN: 0031-8655
• DOI: 10.1043/0031-8655(2003)077(0339:AVSOTE)2.0.CO;2

The protozoan ciliate Stentor coeruleus displays a step-up photophobic response to an increase in light intensity in its environment. The motile response consists of a delayed stop of ciliary beating and transient ciliary reversal period. Such light-avoiding behavior was significantly influenced by an incubation of cells with l -cis -diltiazem, a common blocker of cyclic guanosine monophosphate (cGMP)-gated ion channel conductance. The introduction of l -cis -diltiazem to the medium induced ciliary reversal in control cells, mimicking the step-up photophobic response. In light-stimulated ciliates, the presence of this inhibitor caused a substantial decrease of the latency of ciliary stop response, prolongation of the ciliary reversal duration and also an increase of cell photoresponsiveness in a dose- and time-dependent manner. The obtained behavioral results support the suggestion that the photosensitive ciliate S. coeruleus possesses cGMP-gated channels, which may be involved in the process of light signal transduction for the motile photophobic response.