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Postnatal maturation of the GABAergic system in rat neocortex
1Department of Neurology and Neurological Sciences, Stanford University School of Medicine, California 94305.
Journal of Neurophysiology
|February 1, 1991
Summary
This study reveals how inhibitory circuits mature in the rat brain, showing that GABAergic responses strengthen with age. Key findings highlight developmental changes in neurotransmitter receptor function critical for brain development.
Area of Science:
- Neuroscience
- Developmental Neuroscience
- Cortical Circuitry
Background:
- Intracortical inhibitory circuitry undergoes significant postnatal maturation.
- Understanding the developmental trajectory of gamma-aminobutyric acid (GABA) and baclofen responses is crucial for comprehending neural network development.
Purpose of the Study:
- To investigate the postnatal maturation of intracortical inhibitory circuitry.
- To examine the development of neuronal responses to GABA and baclofen in rat cortical neurons.
Main Methods:
- In vitro electrophysiological recordings from rat primary somatosensory and visual cortex neurons (layers II and III).
- Studied spontaneous inhibitory postsynaptic potentials (IPSPs) and evoked responses following electrical stimulation.
- Utilized receptor antagonists (bicuculline methiodide, D-APV) and focal application of GABA to assess receptor function.
Main Results:
- Spontaneous IPSPs mediated by GABAA receptors were present across all studied ages (postnatal days 4-41).
- Evoked fast and late IPSPs, along with their peak conductance, significantly increased from juvenile to adult stages.
- Immature neurons showed NMDA receptor-mediated excitatory postsynaptic potentials (EPSPs) concurrent with IPSPs, an effect diminished in adults.
Conclusions:
- Cortical inhibitory circuitry undergoes substantial functional maturation postnatally, characterized by strengthening of GABAergic transmission.
- Developmental changes in NMDA receptor co-activation influence the integration of excitatory and inhibitory inputs.
- The triphasic GABA response in mature neurons indicates complex GABAA and GABAB receptor roles in cortical inhibition.