Photosensitive signal transduction induces membrane hyperpolarization in Paramecium bursaria.
The protozoan ciliate Paramecium bursaria exhibits membrane hyperpolarization in response to photostimulation, accompanied with an increased swimming speed. The external addition of cyclic nucleotide phosphodiesterase (PDE) inhibitors, either theophylline (1,3-dimethylxanthine) or 3-isobutyl-1-methylxanthin (IBMX), increased in both amplitudes of the membrane hyperpolarization and the increase in swimming speed. Moreover, the addition of membrane permeable cyclic nucleotide analogs, either 8-bromo-adenosine 3',5'-cyclic monophosphate (Br-cAMP) or 8-Br-guanosine 3',5'-cyclic monophosphate (Br-cGMP), increased these amplitudes. On the other hand, the addition of l-cis-diltiazem, known to block the conductance of cyclic nucleotide-gated channels, partially decreased both amplitudes of the membrane hyperpolarization and the increase in swimming speed. An enzyme immunoassay of cellular cyclic nucleotide contents showed that photostimulation induced a rapid increase in adenosine 3',5'-cyclic monophosphate (cAMP), but little increase in guanosine 3',5'-cyclic monophosphate (cGMP), raising the possibility that a rapid increase in cAMP mediates the light-induced hyperpolarization in P. bursaria.
Mitarai
Atsushi
A
Biophysical Dynamics Laboratories, Graduate School of Frontier Bioscience, Osaka University, Toyonaka, Osaka 560-8531, Japan.
Nakaoka
Yasuo
Y
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives / Q000494:pharmacology; D004110:Diltiazem / Q000494:pharmacology; D008027:Light; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects; D009068:Movement / Q000187:drug effects / Q000528:radiation effects; D010247:Paramecium / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010775:Photic Stimulation; D017319:Photosensitizing Agents / Q000494:pharmacology*; D015398:Signal Transduction / Q000187:drug effects / Q000528:radiation effects
D010726:Phosphodiesterase Inhibitors; D017319:Photosensitizing Agents; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D000242:Cyclic AMP; D004110:Diltiazem; D006152:Cyclic GMP