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Updated: Jun 22, 2026

Real-time Electrophysiology: Using Closed-loop Protocols to Probe Neuronal Dynamics and Beyond
Published on: June 24, 2015
Proximity of excitatory and inhibitory axon terminals adjacent to pyramidal cell bodies provides a putative basis for
Angel Merchán-Pérez1, José-Rodrigo Rodriguez, Charles E Ribak
1Department of Anatomy I, School of Medicine, Universidad Complutense, 28040 Madrid, Spain. amerchan@med.ucm.es
Abstract:
Although pyramidal cells are the main excitatory neurons in the cerebral cortex, it has recently been reported that they can evoke inhibitory postsynaptic currents in neighboring pyramidal neurons. These inhibitory effects were proposed to be mediated by putative axo-axonic excitatory synapses between the axon terminals of pyramidal cells and perisomatic inhibitory axon terminals [Ren M, Yoshimura Y, Takada N, Horibe S, Komatsu Y (2007) Science 316:758-761]. However, the existence of this type of axo-axonic synapse was not found using serial section electron microscopy. Instead, we observed that inhibitory axon terminals synapsing on pyramidal cell bodies were frequently apposed by terminals that established excitatory synapses with neighbouring dendrites. We propose that a spillover of glutamate from these excitatory synapses can activate the adjacent inhibitory axo-somatic terminals.
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