TRPA1 Channels Are Regulators of Astrocyte Basal Calcium Levels and Long-Term Potentiation via Constitutive D-Serine Release

Astrocytes are found throughout the brain where they make extensive contacts with neurons and synapses. Astrocytes are known to display intracellular Ca2+ signals and release signaling molecules such as D-serine into the extracellular space. However, the role(s) of astrocyte Ca2+ signals in hippocampal long-term potentiation (LTP), a form of synaptic plasticity involved in learning and memory, remains unclear. Here, we explored a recently discovered novel TRPA1 channel-mediated transmembrane Ca2+ flux pathway in astrocytes. Specifically, we determined whether block or genetic deletion of TRPA1 channels affected LTP of Schaffer collateral to CA1 pyramidal neuron synapses. Using pharmacology, TRPA1(-/-) mice, imaging, electrophysiology, and D-serine biosensors, our data indicate that astrocyte TRPA1 channels contribute to basal Ca2+ levels and are required for constitutive D-serine release into the extracellular space, which contributes to NMDA receptor-dependent LTP. The findings have broad relevance for the study of astrocyte-neuron interactions by demonstrating how TRPA1 channel-mediated fluxes contribute to astrocyte basal Ca2+ levels and neuronal function via constitutive D-serine release.