Synaptic dysfunction and adaptation after NMDA receptor ablation in the mouse medial prefrontal cortex

Area of Science:

• Neuroscience
• Molecular Biology
• Psychiatry

Background:

• N-methyl-D-aspartate receptors (NMDARs) in the prefrontal cortex (PFC) regulate neuronal excitability and cognition.
• NMDAR dysfunction is implicated in schizophrenia, potentially due to altered glutamatergic signaling.
• The impact of progressive adolescent NMDAR loss on PFC excitatory synapses remains unclear.

Purpose of the Study:

• To investigate the effects of ablating NMDAR expression in adolescent mouse PFC on excitatory synaptic structure and function.
• To explore potential compensatory mechanisms in PFC networks following NMDAR loss.

Main Methods:

• In vivo genome editing to ablate the Grin1 gene (encoding NMDAR GluN1 subunit) in medial PFC neurons of adolescent mice.
• Whole-cell patch-clamp electrophysiology and confocal imaging of dendritic spines in layer V pyramidal neurons.

Main Results:

• NMDAR ablation led to an initial decrease in basilar dendritic spine density.
• A subsequent rebound in spine density and increased AMPA receptor-mediated (AMPAR) synaptic transmission were observed.
• These effects were specific to pan-neuronal NMDAR ablation, not observed with targeted excitatory neuron manipulation.

Conclusions:

• Progressive NMDAR loss in the adolescent PFC triggers a cascading reorganization of local neuronal networks.
• Compensatory processes may occur to maintain allostasis but could be impaired in disease states like schizophrenia.