title: Photosensitive signal transduction induces membrane hyperpolarization in Paramecium bursaria.
abstract: 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.
authors: Biophysical Dynamics Laboratories, Graduate School of Frontier Bioscience, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors: Atsushi
authors: A
authors: Mitarai
authors: Yasuo
authors: Y
authors: Nakaoka
mesh_terms: 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
chemical_list: D010726:Phosphodiesterase Inhibitors; D017319:Photosensitizing Agents; D015124:8-Bromo Cyclic Adenosine Monophosphate; C016276:8-bromocyclic GMP; D000242:Cyclic AMP; D004110:Diltiazem; D006152:Cyclic GMP