Single synapses control mossy cell firing

Abstract

The function of mossy cells (MCs) in the dentate gyrus has remained elusive. Here we determined the functional impact of single mossy fibre (MF) synapses on MC firing in mouse entorhino-hippocampal slice cultures. We stimulated single MF boutons and recorded Ca2+ transients in the postsynaptic spine and unitary excitatory postsynaptic potentials (EPSPs) at the MC soma. Synaptic responses to single presynaptic stimuli varied strongly between different MF synapses, even if they were located on the same MC dendrite. Synaptic strengths ranged from subthreshold EPSPs to direct postsynaptic action potential (AP) generation. Induction of synaptic plasticity at these individual MF synapses resulted in potentiation or depression depending on the initially encountered synaptic state, indicating that synaptic transmission at MF synapses on MCs is determined by their previous functional history. With these unique functional properties MF-MC synapses control MC firing individually thereby enabling modulation of the dentate network by single granule cells.