Astrocyte-induced modulation of synaptic transmission

The idea that astrocytes simply provide structural and trophic support to neurons has been challenged by recent evidence demonstrating that astrocytes exhibit a form of excitability and communication based on intracellular Ca²⁺ variations and intercellular Ca²⁺ waves, which can be initiated by neuronal activity. These astrocyte Ca²⁺ variations have now been shown to induce glutamate-dependent Ca²⁺ elevations and slow inward currents in neurons. More recently, it has been demonstrated that synaptic transmission between cultured hippocampal neurons can be directly modulated by astrocytes. We have reported that astrocyte stimulation can increase the frequency of miniature synaptic currents. Furthermore, we also have demonstrated that an elevation in the intracellular Ca²⁺ in astrocytes induces a reduction in both excitatory and inhibitory evoked synaptic transmission through the activation of selective presynaptic metabotropic glutamate receptors.