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Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels
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Single-Cell Calcium Imaging for Studying the Activation of Calcium Ion Channels

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[Dual action of intracellularly released calcium on the quantal mediator secretion]

O P Balezina, A N Bukiia, V I Lapteva

    Rossiiskii Fiziologicheskii Zhurnal Imeni I.M. Sechenova
    |March 19, 2005
    PubMed

    Insights

    Ryanodine influences neurotransmitter release by affecting calcium stores in nerve terminals. Its effects can be either inhibitory or excitatory depending on calcium levels and nerve activity.

    Area of Science:

    • Neuroscience
    • Molecular Biology
    • Muscle Physiology

    Background:

    • Neurotransmitter release is crucial for synaptic function.
    • Intracellular calcium stores play a significant role in regulating neurotransmitter release.
    • Ryanodine is known to interact with calcium release channels.

    Purpose of the Study:

    • To investigate the effect of ryanodine on spontaneous and evoked neurotransmitter release.
    • To determine how ryanodine's action is modulated by different calcium loads and stimulation frequencies.
    • To elucidate the role of intraterminal calcium stores in synaptic transmission.

    Main Methods:

    • Experiments conducted on mouse diaphragm muscle using microelectrode techniques.
    • Assessment of spontaneous and evoked mediator release under varying potassium-induced depolarization (8-16 mM [K+]ex).
    • Evaluation of ryanodine's effects during rhythmic motor nerve terminal stimulation (4-100 Hz).

    Main Results:

    • Low calcium load increased miniature and plate potentials (MEPPs) frequency, inhibited by ryanodine.
    • High calcium load led to a significant increase in MEPPs frequency, further enhanced by ryanodine.
    • Ryanodine modulated excitatory postsynaptic potential (EPP) amplitude, decreasing it at low frequencies and increasing it at high frequencies.

    Conclusions:

    • Ryanodine-induced calcium release from intraterminal stores has a dual effect on neurotransmitter release.
    • The action of ryanodine is dependent on the intraterminal calcium load and synaptic activity patterns.
    • This highlights the complex role of intracellular calcium dynamics in synaptic transmission.

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