Short-term synaptic depression is a fundamental property of synapses, thought mainly to depend on mechanisms inherent to the presynaptic terminal. We show that hippocampal glutamate synapses, in the rat hippocampal CA1 area of stratum radiatum, exhibit a large depression of presynaptic release probability following a short synaptic burst. This depression is elicited using a brief high frequency train and affects both the recently active (< 1 s) synapses (post-burst depression) as well as inactive neighbouring synapses (transient heterosynaptic depression). This astrocyte- mediated depression is abolished by inhibiting astrocyte metabolism and astrocyte calcium signalling. Our results suggest that the astrocyte part of the tripartite synapse is actively involved in short-term synaptic depression