title: Electrical responses of the marine ciliate Euplotes vannus (hypotrichia) to mechanical stimulation at the posterior cell end.
abstract: Electrical responses upon mechanostimulation at the posterior cell end were investigated in the marine hypotrichous ciliate Euplotes vannus. A new mechanostimulator was developed to mimic stimuli that are identical with those involved in cell-cell collisions. The receptor potential hyperpolarized by 18-35 mV within 12-25 msec, reached a peak value of -62 mV with a delay of 4-9 msec after membrane deformation, and was deactivated after 50-70 msec. Cirri were stimulated to beat accelerated backward. The corresponding receptor current exerted a similar time course with a peak of 2.4 nA. The shift of the reversal potential by 57.6 mV at a tenfold increase of [K+]o identifies potassium ions as current carriers within the development of the receptor potential. An intracellular K concentration of 355 mmol/liter was calculated for cells in a medium that was composed similar to sea-water. The mechanically activated potassium current was totally inhibited by extracellular TEA and intracellular Cs+, and partially inhibited by extracellular 4-AP. The total inhibition of the current by injected EGTA points to a Ca dependence of the posterior mechanosensitivity. It was confirmed by the increase of the peak current amplitude with rising [Ca2+]o. Sodium presumably repolarizes the receptor potential because the repolarization was delayed and after-depolarizations were eliminated in media without sodium. Since deciliation did not affect mechanosensitivity, the corresponding ion channels reside within the soma membrane.
authors.affiliation: Universität Osnabrück, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Krüppel
authors.forename: V
authors.initials: V
authors.lastname: Furchbrich
authors.forename: W
authors.initials: W
authors.lastname: Leuken
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002462:Cell Membrane / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D016812:Euplotes / Q000502:physiology* / Q000648:ultrastructure; D008465:Mechanoreceptors / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013314:Stress, Mechanical
chemical_list: D000644:Quaternary Ammonium Compounds; D004533:Egtazic Acid; D012964:Sodium; C027917:tetramethylammonium; D002118:Calcium