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Glutamate inhibits GABA excitatory activity in developing neurons
A N van den Pol1, X B Gao, P R Patrylo
1Department of Neurosurgery, Yale University, New Haven, Connecticut 06520, USA.
Summary
In developing brains, glutamate inhibits the excitatory effects of GABA, a key neurotransmitter. This glutamate-mediated inhibition occurs at both presynaptic and postsynaptic sites, preventing overexcitation during early brain development.
Area of Science:
- Neuroscience
- Developmental Biology
Background:
- Gamma-aminobutyric acid (GABA) acts as an excitatory neurotransmitter in the developing brain, unlike its inhibitory role in mature brains.
- Excitatory GABA leads to neuronal depolarization, increased intracellular calcium, and action potentials, crucial for early neural development.
Purpose of the Study:
- To investigate the inhibitory role of glutamate on the excitatory actions of GABA in developing neurons.
- To identify the specific mechanisms and receptor subtypes involved in glutamate's modulation of GABAergic activity.
Main Methods:
- Utilized fura-2 digital imaging and whole-cell recording techniques.
- Examined neuronal activity in cultured hypothalamic neurons and brain slices from developing brain regions.
- Analyzed the expression of metabotropic glutamate receptors (mGluRs) using Northern blots.
Main Results:
- Glutamate reduces GABA-evoked calcium increases, partly via group II mGluRs.
- Activation of group III mGluRs significantly inhibits GABA release at early synapses.
- Inhibitory effects of group III mGluRs on excitatory GABA were observed across developing hypothalamic, cortical, and spinal cord neurons.
- Group III mGluR antagonists enhanced GABA activity, indicating ongoing glutamate-mediated inhibition.
- Northern blot analysis confirmed early expression of various mGluRs during synaptogenesis.
Conclusions:
- Glutamate exerts inhibitory control over excitatory GABA actions at both presynaptic and postsynaptic levels in developing neurons.
- This glutamate-mediated inhibition is a critical mechanism preventing excessive neuronal excitation during early brain development.
- Glutamate's modulatory role on GABAergic calcium signaling influences crucial developmental processes like neuronal migration and synapse formation.