Alternating sources of perisomatic inhibition during behavior

Area of Science:

• Neuroscience
• Cellular Neuroscience
• Systems Neuroscience

Background:

• Two main GABAergic interneurons, cholecystokinin (CCK) and parvalbumin (PV), regulate hippocampal pyramidal cell output.
• While PV interneuron activity is well-understood, CCK interneuron recruitment patterns in vivo remain largely unknown.

Purpose of the Study:

• To investigate the in vivo activity patterns of CCK-expressing basket cells (BCs) in the mouse hippocampus.
• To elucidate the relationship between CCK BCs, PV interneurons, and pyramidal cells during spontaneous behavior.

Main Methods:

• In vivo electrophysiological recordings in the CA1 region of the mouse hippocampus.
• Analysis of neuronal activity at behaviorally relevant timescales (seconds).
• Intervention experiments to probe the functional interactions between CCK and PV systems.

Main Results:

• CCK BC activity inversely scales with both PV interneuron and pyramidal cell activity.
• PV interneurons exert powerful inhibitory control over CCK BCs.
• This inverse coupling suggests a mechanism for brain-state-specific segregation of inhibition.

Conclusions:

• CCK and PV interneurons form a tightly coupled, complementary inhibitory system in the hippocampus.
• The findings reveal a novel form of inhibitory segregation during spontaneous behavior, mediated by the PV-CCK circuit.
• This study advances our understanding of hippocampal microcircuit regulation and its role in brain states.