Functionally Distinct Circuits Are Linked by Heterocellular Electrical Synapses in the Thalamic Reticular Nucleus

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Systems Neuroscience

Background:

• The thalamic reticular nucleus (TRN) regulates sensory attention, sleep, and wake states by inhibiting thalamocortical neurons.
• Two distinct TRN neuron subtypes, calbindin-expressing (CB) and somatostatin-expressing (SOM), have been identified with differing connectivity patterns.

Purpose of the Study:

• To investigate the presence and nature of electrical synapses between CB and SOM TRN neuron subtypes.
• To determine if electrical synapses functionally link first-order and higher-order thalamic channels within the TRN.

Main Methods:

• Utilized GFP reporter mice to specifically label and record from CB and SOM TRN neurons.
• Electrophysiological recordings were performed to confirm subtype differentiation and identify electrical synaptic connections.

Main Results:

• Confirmed that GFP expression accurately distinguishes CB and SOM TRN neuron subtypes based on electrophysiological properties.
• Identified electrical synapses forming both homocellular (within subtype) and heterocellular (across subtypes) connections between TRN neurons.

Conclusions:

• Electrical synapses are prevalent within the TRN, connecting both CB and SOM neuron subtypes.
• These electrical synapses provide a substrate for functionally integrating first-order and higher-order thalamocortical channels within the TRN, influencing information flow.