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Vibrodissociation of Neurons from Rodent Brain Slices to Study Synaptic Transmission and Image Presynaptic Terminals
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GABAB receptors modulate an omega-conotoxin-sensitive calcium current that is required for synaptic transmission in

M J Wall1, N Dale

  • 1School of Biological Sciences, Bristol University, United Kingdom.

The Journal of Neuroscience : the Official Journal of the Society for Neuroscience
|October 1, 1994
PubMed

Insights

Activation of GABAB receptors in Xenopus embryos inhibits neurotransmitter release by reducing specific calcium (Ca2+) currents. This finding clarifies mechanisms of presynaptic inhibition in the vertebrate nervous system.

Area of Science:

  • Neuroscience
  • Molecular Biology
  • Developmental Biology

Background:

  • GABAB receptors modulate neuronal excitability and transmitter release.
  • Presynaptic inhibition by GABAB receptors is known but underlying mechanisms require elucidation.
  • Xenopus embryo spinal neurons provide a model system for studying these mechanisms.

Purpose of the Study:

  • To investigate the cellular and molecular mechanisms of GABAB receptor action in Xenopus embryo spinal neurons.
  • To identify the specific ion currents modulated by GABAB receptor activation.
  • To determine the role of these currents in synaptic transmission.

Main Methods:

  • Whole-cell voltage-clamp recordings from isolated Xenopus embryo spinal neurons.
  • Application of GABAB receptor agonist (baclofen) and antagonists (CGP35348, phaclofen, 2-hydroxysaclofen).
  • Pharmacological characterization using omega-conotoxin (omega-CgTX) and assessment of synaptic transmission in the intact spinal cord.

Main Results:

  • Baclofen reversibly reduced Ca2+ current amplitude in a voltage-dependent manner.
  • GABAB antagonists blocked this reduction, confirming GABAB receptor mediation.
  • Baclofen's effect was occluded by omega-CgTX, indicating modulation of an omega-CgTX-sensitive Ca2+ current.
  • omega-CgTX blocked inhibitory synaptic transmission, highlighting the role of this Ca2+ current in transmitter release.

Conclusions:

  • GABAB receptors modulate a specific omega-conotoxin-sensitive Ca2+ current in Xenopus spinal neurons.
  • This Ca2+ current is essential for transmitter release and plays a key role in GABAB receptor-mediated presynaptic inhibition.
  • Findings provide insight into the mechanisms of synaptic modulation in the vertebrate nervous system.

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