Long term imaging in vivo of dendritic spine dynamics on an inhibitory neuronal subclass in the mouse cerebral cortex 

In supragranular layers of the cerebral cortex vasoactive intestinal peptide (VIP)-expressing cells disinhibit excitatory pyramidal cells by inhibiting parvalbumin (PV)- and somatostatin (SST)-expressing interneurons. VIP-cells receive local and long-range cortical inputs as well as inputs from deeper brain areas. In my thesis work we used VIP-cre transgenic mice in combination with AAV-flex-GFP vectors to prove that a multipolar subpopulation of VIP cells carries dendritic spines. Longitudinal in vivo study indicates that the spines turnover at a rate of 0.25 per 4 days and have lower survival fractions than pyramidal cell spines. Electron microscopy showed that spines form excitatory synapses. Mono-synaptic tracing confirmed that their inputs are local, thalamic as well as other long-range projections. We conclude that a group of VIP cells receive excitatory inputs on structurally dynamic spines and their high degree of plasticity may regulate the strength and the source of their excitation, and thereby shape network disinhibition