Membrane potential fluctuation in paramecium

Majima, Toshikazu

doi:10.1016/0301-4622(80)85012-5

Cited by 19 publications

(12 citation statements)

References 15 publications

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“…Physiologically, the resting membrane potential in Paramecium is about -25mV and displays random fluctuations of small amplitude (Majima, 1980;Moolenaar et al, 1976). Larger fluctuations generate a more extensive, spike-like depolarization that is accompanied by both the opening of Ca 2+ channels localized in the ciliary membrane (Dunlap, 1977;Ogura and Takahashi, 1976) and by a simultaneous influx of Ca…”

Section: Discussionmentioning

confidence: 99%

γ-Amino butyric acid (GABA) release in the ciliated protozoonParameciumoccurs by neuronal-like exocytosis

Ramoino

Milanese

Candiani

et al. 2010

Journal of Experimental Biology

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SUMMARYParamecium primaurelia expresses a significant amount of -amino butyric acid (GABA). Paramecia possess both glutamate decarboxylase (GAD)-like and vesicular GABA transporter (vGAT)-like proteins, indicating the ability to synthesize GABA from glutamate and to transport GABA into vesicles. Using antibodies raised against mammalian GAD and vGAT, bands with an apparent molecular weight of about 67kDa and 57kDa were detected. The presence of these bands indicated a similarity between the proteins in Paramecium and in mammals. VAMP, syntaxin and SNAP, putative proteins of the release machinery that form the so-called SNARE complex, are present in Paramecium. Most VAMP, syntaxin and SNAP fluorescence is localized in spots that vary in size and density and are primarily distributed near the plasma membrane. Antibodies raised against mammal VAMP-3, sintaxin-1 or SNAP-25 revealed protein immunoblot bands having molecular weights consistent with those observed in mammals. Moreover, P. primaurelia spontaneously releases GABA into the environment, and this neurotransmitter release significantly increases after membrane depolarization. The depolarization-induced GABA release was strongly reduced not only in the absence of extracellular Ca 2+ but also by pre-incubation with bafilomycin A1 or with botulinum toxin C1 serotype. It can be concluded that GABA occurs in Paramecium, where it is probably stored in vesicles capable of fusion with the cell membrane; accordingly, GABA can be released from Paramecium by stimulus-induced, neuronal-like exocytotic mechanisms.

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Section: Discussionmentioning

confidence: 99%

γ-Amino butyric acid (GABA) release in the ciliated protozoonParameciumoccurs by neuronal-like exocytosis

Ramoino

Milanese

Candiani

et al. 2010

Journal of Experimental Biology

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“…The intracellular electric potential of a paramecium cell fixed on a plate was measured by inserting a glass microelectrode. The potential fluctuation appeared to consist of two components (Majima, 1980). The basic fluctuation has an average amplitude of one to a few mV.…”

Section: (Ii) Comparison With Experimental Datamentioning

confidence: 99%

“…The potential was usually about −20 to −30 mV on average. It was not kept constant, but showed a random fluctuation of the amplitude of one to a few mV, including a sharp spikelike fluctuation of a larger amplitude (Moolenaar et al, 1976;Majima, 1979Majima, , 1980. This spike-like fluctuation was a signal for partial reversal of ciliary beating on the cell surface.…”

Section: Introductionmentioning

confidence: 98%

Spontaneous Signal Generation in Living Cells

Oosawa

2001

Bulletin of Mathematical Biology

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Living cells often generate signals spontaneously in the absence of external stimuli. Those signals play an important role in their tactic behaviors. This paper presents a theoretical treatment on the mechanism of spontaneous signal generation. The mechanism consists of two steps: (1) production of the basic fluctuation of the intracellular electric potential due to the open-closed fluctuation of the gates of ion channels and (2) generation of a spike-like fluctuation of potential depending on the positive shift of the basic fluctuation. The first step is described by an equation of the Langevin type, where the random force is proportional to the circulating ion current across the membrane; the average of the square of the random force is proportional to the rate of free-energy consumption by the current. The second step is described by a rate equation of transition of field-sensitive channel gates which contains the fluctuating electric field in the exponential term. There, the fluctuation has a nonlinear effect. Such a two-step process may work in various kinds of living cells. The presence of circulating ion current in the resting state is a most important key. Some cells may be quiet and some cells may be active to generate spontaneous signals.

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“…Therefore, the membrane potential fluctuation was interpreted to be mainly due to the fluctuation of K + channels. However, Majima indicated that Ca 2+ current also makes contributions to the membrane potential fluctuation after experiments with various concentrations of K + and Ca 2+ (Majima, 1980). The membrane potential fluctuation increased with an increase in the motive force of the Ca 2+ current.…”

Section: Introductionmentioning

confidence: 99%

“…The resting membrane potential, which on average is about -25 mV, is not kept constant but instead displays a random amplitude fluctuation of about 1-3 mV (Majima, 1980;Moolenaar et al, 1976). When the resting potential fluctuation reaches a positive level, a spikelike depolarization of much larger amplitude is frequently generated.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous fluctuation of the resting membrane potential inParamecium: amplification caused by intracellular Ca2+

Nakaoka

Imaji

Hara

et al. 2009

Journal of Experimental Biology

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SUMMARY The ciliated protozoan Paramecium spontaneously changes its swimming direction in the absence of external stimuli. Such behavior is based on resting potential fluctuations, the amplitudes of which reach a few mV. When the resting potential fluctuation is positive and large, a spike-like depolarization is frequently elicited that reverses the beating of the cilia associated with directional changes during swimming. We aimed to study how the resting potential fluctuation is amplified. Simultaneous measurements of the resting potential and intracellular Ca2+([Ca2+]i) from a deciliated cell showed that positive potential fluctuations were frequently accompanied by a small increase in[Ca2+]i. This result suggests that Ca2+influx through the somatic membrane occurs during the resting state. The mean amplitude of the resting potential fluctuation was largely decreased by either an intracellular injection of a calcium chelater (BAPTA) or by an extracellular addition of Ba2+. Hence, a small increase in[Ca2+]i amplifies the resting potential fluctuation. Simulation analysis of the potential fluctuation was made by assuming that Ca2+ and K+ channels of surface membrane are fluctuating between open and closed states. The simulated fluctuation increased to exhibit almost the same amplitude as the measured fluctuation using the assumption that a small Ca2+ influx activates Ca2+ channels in a positive feedback manner.

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Membrane potential fluctuation in paramecium

Cited by 19 publications

References 15 publications

γ-Amino butyric acid (GABA) release in the ciliated protozoonParameciumoccurs by neuronal-like exocytosis

γ-Amino butyric acid (GABA) release in the ciliated protozoonParameciumoccurs by neuronal-like exocytosis

Spontaneous Signal Generation in Living Cells

Spontaneous fluctuation of the resting membrane potential inParamecium: amplification caused by intracellular Ca2+

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