Electrical coupling among irregular-spiking GABAergic interneurons expressing cannabinoid receptors

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Systems Neuroscience

Background:

• Cannabinoid receptor-1 (CB1) is found in specific GABAergic interneurons.
• These neurons are implicated in cognitive functions and brain rhythm regulation.
• The detailed physiology and connectivity of neocortical CB1-expressing interneurons are not well understood.

Purpose of the Study:

• To characterize the morphology, physiology, and synaptic connectivity of CB1-expressing interneurons in the mouse neocortex.
• To investigate the presence and function of electrical synapses between these interneurons.

Main Methods:

• Patch-clamp recordings in mouse neocortical slices.
• Identification of CB1-expressing interneurons based on morphology and electrophysiological properties (irregular spiking).
• Paired recordings to assess electrical coupling and synaptic connections.

Main Results:

• A population of CB1-expressing interneurons (CB1-IS) was identified in layer II/III.
• These cells exhibit multipolar/bitufted morphology, wide axonal projection, and irregular spiking.
• CB1-IS cells form inhibitory GABAA synapses onto pyramidal cells and other CB1-IS cells.
• A high proportion (90%) of CB1-IS cells were electrically coupled, with a 6% average coupling coefficient.
• Electrical coupling facilitated coordinated firing among CB1-IS cells.

Conclusions:

• A distinct population of electrically coupled, GABAergic CB1-IS interneurons exists in the neocortex.
• These neurons possess unique morphological and electrophysiological features.
• Their electrical and chemical synaptic interactions likely contribute to neocortical network activity and cannabinoid-mediated cognitive effects.