In 2009 the research group of Alfonso Araque publishes a review paper titled “Tripartite synapses: astrocytes process and control synaptic information”.
The term “tripartite synapse” was proposed in 1999.
Astrocyte Ca2+ signal has a fundamental role in neuron–astrocyte communication as the cellular signal triggered by the neuronal activity and responsible for transmitter release from astrocytes and the consequent neuromodulation.
They even refer to an “astrocytic revolution in current neuroscience”. Everything started in the early 1990s with the first fluorescence imaging experiments of intracellular calcium concentrations in living astrocytes. The data revelead the excitability of astrocytes, that were till then considered non-excitable cells.