Recent evidences demonstrate the bidirectional communication between astrocytes and neurons. Astrocytes respond to neuronal activity with intracellular calcium variations and release different gliotransmitters that modulate neuronal and synaptic activity. This communication has been widely described in rat and mouse brains; however the existence of this intercellular signalling in human brain is unknown. Therefore, the aim of this study is to determine and characterize the cellular and molecular mechanisms of the neuron-astrocyte communication in human brain.

We have used electrophysiological and calcium imaging techniques on human brain slices (hippocampus and mesial cortex) from biopsies of epileptic patients.

We have found that: 

1) Human astrocytes show intrinsic excitability based on intracellular calcium oscillations that are independent of neuronal activity.

2) Astrocytes exhibit functional receptors for glutamate and ATP that after their activation induce calcium elevations.

3) The activation of astrocytes evokes slow inward currents in neurons, modifying the neuronal excitability.

Therefore, these results indicate that there is a communication between astrocytes and neurons in human tissue, suggesting the existence of a new signalling pathway in human brain.

Supported by: FIS (PI060349) to RGS, MEC (BFU2004-0448) and EC (Health-F2-2007-202167) to AA.