Specific hippocampal interneurons shape consolidation of recognition memory

SUMMARY A complex array of different inhibitory interneurons tightly controls hippocampal activity, but how such diversity specifically impacts on memory processes is scantly known. We found that a small subclass of type-1 cannabinoid receptor (CB 1 )-expressing hippocampal interneurons determines episodic-like memory consolidation by linking dopamine D 1 receptor signaling to GABAergic transmission. Mice lacking CB 1 in D 1 -positive cells (D 1 - CB 1 -KO) displayed impaired long-term, but not short-term, object recognition memory. Re-expression of CB 1 in hippocampal, but not striatal, D 1 -positive cells rescued this memory impairment. Learning induced a facilitation of in vivo hippocampal long-term potentiation (LTP), which was abolished in mutant mice. Chemogenetic and pharmacological experiments revealed that both CB 1 -mediated memory and associated LTP facilitation involves the local control of GABAergic inhibition in a D 1 -dependent manner. This study reveals that CB 1 -/D 1 -expressing interneurons shape hippocampal circuits to sustain recognition memory, thereby identifying a mechanism linking the diversity of hippocampal interneurons to specific behavioral and cognitive outcomes.