Thalamic Gap Junctions Control Local Neuronal Synchrony and Influence Macroscopic Oscillation Amplitude during EEG...

Area of Science:

• Neuroscience
• Neurophysiology

Background:

• Alpha (α) rhythms (8-13 Hz) are linked to perception, not just brain idling.
• A proposed mechanism involves specialized thalamocortical (TC) neurons in the lateral geniculate nucleus (LGN) interconnected by gap junctions (GJs).
• Evidence for GJ involvement in thalamic α rhythms primarily comes from in vitro studies, with a lack of direct anatomical evidence in the LGN.

Purpose of the Study:

• To investigate the role of GJ inhibitors in suppressing LGN and EEG α rhythms in vivo.
• To provide direct anatomical evidence of neuronal GJs within the LGN.
• To determine if GJs are present between TC neurons or interneurons.

Main Methods:

• Administered GJ inhibitors (carbenoxolone and 18β-glycyrrhetinic acid) to the LGN via reverse microdialysis in behaving cats.
• Recorded spontaneous LGN and EEG α rhythms.
• Examined the effect of carbenoxolone on LGN unit activity.
• Utilized electron microscopy to identify ultrastructural evidence of GJs in the cat LGN.

Main Results:

• Both GJ inhibitors (18β-GA and CBX) reversibly suppressed LGN and EEG α rhythms.
• Carbenoxolone also decreased neuronal synchrony.
• Electron microscopy provided definitive ultrastructural evidence of GJs between neurons in the cat LGN.
• Absence of GJ coupling in interneurons suggests GJs are located between TC neurons.

Conclusions:

• Thalamic GJs play a significant role in generating and modulating LGN and EEG α rhythms in vivo.
• These findings provide direct anatomical and functional evidence for the involvement of TC neuron GJs in α rhythms.
• This study bridges macroscopic α rhythm observations with underlying cellular mechanisms in the LGN.