Astrocytic perisynaptic processes (PAPs), which envelope excitatory synapses, respond to long-term potentiation (LTP) induction by modifying their morphology, but the underlying mechanisms are unclear. Here, the morphological changes in PAPs were shown to depend on increases in intracellular calcium levels and activation of astrocytic metabotropic glutamate receptors. Furthermore, whisker stimulation increased PAP motility in the somatosensory cortex, suggesting that signalling between neurons and astrocytes regulates PAP structural plasticity.