Corticothalamic inhibition in the thalamic reticular nucleus

Area of Science:

• Neuroscience
• Computational Neuroscience

Background:

• The thalamic reticular nucleus (RTN) uses mutual inhibition to regulate thalamocortical network oscillations.
• Excitatory cortical inputs to the RTN are known to induce spindle oscillations.

Purpose of the Study:

• To investigate how corticothalamic influences engage the inhibitory network within the RTN.
• To explore the mechanisms by which cortical excitation spreads inhibition throughout the RTN.

Main Methods:

• Focal electrical stimulation of layer VI in the mouse barrel cortex in vitro.
• Recording of inhibitory postsynaptic currents (IPSCs) in RTN cells.
• Application of ionotropic glutamate receptor and GABA(A) receptor antagonists.

Main Results:

• Cortical stimulation induced prominent di- or polysynaptic inhibitory postsynaptic currents (IPSCs) in RTN cells.
• The majority of responses were predominantly inhibitory or purely inhibitory, suggesting local inhibition of neighboring RTN cells.
• Spontaneous and evoked IPSCs were dependent on GABA(A) receptors, indicating functional intrareticular inhibitory connections.

Conclusions:

• Cortical excitation effectively recruits a substantial network of intrareticular inhibitory connections.
• Activation of the RTN by the somatosensory cortex can disynaptically engage the entire inhibitory network via local and reentrant GABA(A) receptor-based synapses.
• This mechanism spreads corticothalamic influence throughout the RTN, contributing to spindle oscillation generation.