GABAergic synapses onto SST and PV interneurons in the CA1 hippocampal region show cell-specific and integrin-dependent plasticity

It is known that GABAergic transmission onto pyramidal neurons shows different forms of plasticity. However, GABAergic cells innervate also other inhibitory interneurons and plasticity phenomena at these projections remain largely unknown. Several mechanisms underlying plastic changes, both at inhibitory and excitatory synapses, show dependence on integrins, key proteins mediating interaction between intra- and extracellular environment. We thus used hippocampal slices to address the impact of integrins on long-term plasticity of GABAergic synapses on specific inhibitory interneurons (containing parvalbumin, PV + or somatostatin, SST +) known to innervate distinct parts of principal cells. Administration of RGD sequence-containing peptide induced inhibitory long-term potentiation (iLTP) at fast-spiking (FS) PV + as well as on SST + interneurons. Interestingly, treatment with a more specific peptide GA(C)RRETAWA(C)GA (RRETAWA), affecting α5β1 integrins, resulted in iLTP in SST + and iLTD in FS PV + interneurons. Brief exposure to NMDA is known to induce iLTP at GABAergic synapses on pyramidal cells. Intriguingly, application of this protocol for considered interneurons evoked iLTP in SST + and iLTD in PV + interneurons. Moreover, we showed that in SST + cells, NMDA-evoked iLTP depends on the incorporation of GABA(A) receptors containing α5 subunit to the synapses, and this iLTP is occluded by RRETAWA peptide, indicating a key role of α5β1 integrins. Altogether, our results revealed that plasticity of inhibitory synapses at GABAergic cells shows interneuron-specificity and show differences in the underlying integrin-dependent mechanisms. This is the first evidence that neuronal disinhibition may be a highly plastic process depending on interneuron type and integrins’ activity.