Figure 2.

Astrocyte mediated metaplasticity. (A) Left: under basal conditions astrocytes release a basal tone of d-serine (green) which is sensed by neuronal NMDARs. Right: when astrocytes are stimulated, for example by the activation of cholinergic fibers, this leads to an increased release of d-serine from the astrocytes, which leads to an increased availability of neuronal NMDARs for activation. (B) Hypothetical BCM curve for the induction of LTP and LTD. Depending on the concentration of astrocyte-derived d-serine, the neuronal activity requirements for induction of LTP and LTD will shift.