Recruitment of Perisomatic Inhibition during Spontaneous Hippocampal Activity In Vitro

Anna Beyeler, Aude Retailleau, Colin Molter, Amine Mehidi, Janos Szabadics, Xavier Leinekugel
PLoS ONE. 2013-06-21; 8(6): e66509
DOI: 10.1371/journal.pone.0066509

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It was recently shown that perisomatic GABAergic inhibitory postsynaptic
potentials (IPSPs) originating from basket and chandelier cells can be recorded
as population IPSPs from the hippocampal pyramidal layer using extracellular
electrodes (eIPSPs). Taking advantage of this approach, we have investigated the
recruitment of perisomatic inhibition during spontaneous hippocampal activity in
vitro. Combining intracellular and extracellular recordings from pyramidal cells
and interneurons, we confirm that inhibitory signals generated by basket cells
can be recorded extracellularly, but our results suggest that, during spontaneous
activity, eIPSPs are mostly confined to the CA3 rather than CA1 region. CA3
eIPSPs produced the powerful time-locked inhibition of multi-unit activity
expected from perisomatic inhibition. Analysis of the temporal dynamics of spike
discharges relative to eIPSPs suggests significant but moderate recruitment of
excitatory and inhibitory neurons within the CA3 network on a 10 ms time scale,
within which neurons recruit each other through recurrent collaterals and trigger
powerful feedback inhibition. Such quantified parameters of neuronal interactions
in the hippocampal network may serve as a basis for future characterisation of
pathological conditions potentially affecting the interactions between excitation
and inhibition in this circuit.

Auteurs Bordeaux Neurocampus