Network stability through homeostatic scaling of excitatory and inhibitory synapses following inactivity in CA3 of rat organotypic hippocampal slice cultures

Homeostatic plasticity is a phenomenon whereby synaptic strength is scaled in the context of the activity that the network receives. Here, we have analysed excitatory and inhibitory synapses in a model of homeostatic plasticity where rat organotypic hippocampal slice cultures were deprived of excitatory synaptic input by the NMDA and AMPA/KA glutamate receptor antagonists, AP5 and CNQX. We show that chronic excitatory synapse deprivation generates an excitable CA3 network where enhanced amplitude and frequency of spontaneous excitatory post-synaptic potentials were associated with increased glutamate receptor subunit expression and increased number and size of synapsin 1 and VGLUT1 positive puncta. Intact spontaneous inhibitory post-synaptic potentials coincided Nvith persistent expression of the GABA-A receptor alpha subunit and GAD65 and an enhancement of parvalbumin-positive puncta. In this model of homeostatic plasticity, scaling up of synaptic excitation and maintenance of fast synaptic inhibition promote an excitable, but stable, CA3 network. (c) 2006 Elsevier Inc. All rights reserved.