Gap Junctions Link Regular-Spiking and Fast-Spiking Interneurons in Layer 5 Somatosensory Cortex

Area of Science:

• Neuroscience
• Cellular Biology

Background:

• Gap junctions form electrical synapses, synchronizing action potential (AP) firing in cortical interneurons (INs).
• These connections were previously thought to occur mainly within functionally similar IN subtypes, forming discrete networks.

Purpose of the Study:

• To investigate the prevalence and functional significance of gap junction coupling between different cortical IN subtypes.
• To challenge the prevailing view of functionally segregated IN networks.

Main Methods:

• Electrophysiological recordings in 16-21 day old mice.
• Analysis of firing properties and electrical coupling probabilities between regular-spiking (RS) and fast-spiking (FS) INs, as well as other IN types (neurogliaform, LTS).

Main Results:

• Electrical coupling probability was similar between and within RS and FS INs.
• Pre-junctional APs were shown to depolarize postsynaptic neurons, increasing firing probability.
• Distinct firing properties were observed between RS/FS INs and neurogliaform/LTS cells.

Conclusions:

• Cortical IN networks are more extensively and heterogeneously coupled by gap junctions than previously understood.
• This widespread electrical connectivity may significantly impact cognitive functions and neurological disorders like epilepsy.