Astroglial CB₁ Receptors Determine Synaptic D-Serine Availability to Enable Recognition Memory

Area of Science:

• Neuroscience
• Astrocyte Biology
• Synaptic Plasticity

Background:

• Astrocytes and neurons communicate bidirectionally, influencing synaptic plasticity and behavior.
• D-serine is crucial for N-methyl-D-aspartate receptor (NMDAR) function, but factors regulating its role in memory are poorly understood.

Purpose of the Study:

• To investigate the role of astroglial cannabinoid receptor 1 (CB1) in regulating D-serine availability and its impact on memory and synaptic plasticity.
• To elucidate the mechanism by which astroglial CB1 receptors influence NMDAR function and cognitive processes.

Main Methods:

• Generated and analyzed GFAP-CB1-KO mice lacking CB1 receptors in astrocytes.
• Assessed object recognition memory and hippocampal long-term potentiation (LTP) in vivo and in vitro.
• Measured intracellular astroglial calcium (Ca2+) levels and extracellular D-serine concentrations.
• Determined NMDAR co-agonist binding site occupancy.

Main Results:

• GFAP-CB1-KO mice exhibited impaired object recognition memory and reduced CA3-CA1 hippocampal LTP.
• Activation of astroglial CB1 receptors increased astroglial Ca2+ and extracellular D-serine.
• GFAP-CB1-KO mice showed lower NMDAR co-agonist site occupancy.
• Supplementation of D-serine fully restored LTP and memory deficits in GFAP-CB1-KO mice.

Conclusions:

• Astroglial CB1 receptors are critical for object recognition memory and hippocampal synaptic plasticity.
• A novel mechanism involves astroglial CB1 receptors controlling D-serine availability to modulate NMDAR function.
• This highlights a key pathway for astroglial regulation of memory and synaptic plasticity.