Mossy fiber synapses on glutamate decarboxylase-immunoreactive neurons: evidence for feed-forward inhibition in the CA3 region of the hippocampus.

Mossy fibers are known to form excitatory synapses on pyramidal neurons in regio inferior of the hippocampus. This study demonstrates that the mossy fibers also establish synaptic contacts with glutamate decarboxylase-immunoreactive, supposedly GABAergic inhibitory neurons in the CA3 region. The observed connection provides a morphological basis for feed-forward inhibition of the pyramidal cells.