Competition and Homeostasis of Excitatory and Inhibitory Connectivity in the Adult Mouse Visual Cortex

M Hadi Saiepour, Sridhara Chakravarthy, Rogier Min, Christiaan N Levelt

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During cortical development, synaptic competition regulates the formation and adjustment of neuronal connectivity. It is unknown whether synaptic competition remains active in the adult brain and how inhibitory neurons participate in this process. Using morphological and electrophysiological measurements, we show that expressing a dominant-negative form of the TrkB receptor (TrkB.T1) in the majority of pyramidal neurons in the adult visual cortex does not affect excitatory synapse densities. This is in stark contrast to the previously reported loss of excitatory input which occurs if the exact same transgene is expressed in sparse neurons at the same age. This indicates that synaptic competition remains active in adulthood. Additionally, we show that interneurons not expressing the TrkB.T1 transgene may have a competitive advantage and obtain more excitatory synapses when most neighboring pyramidal neurons do express the transgene. Finally, we demonstrate that inhibitory synapses onto pyramidal neurons are reduced when TrkB signaling is interfered with in most pyramidal neurons but not when few pyramidal neurons have this deficit. This adjustment of inhibitory innervation is therefore not a cell-autonomous consequence of decreased TrkB signaling but more likely a homeostatic mechanism compensating for activity changes at the population level.

Originele taal-2Engels
Pagina's (van-tot)3713-22
Aantal pagina's10
TijdschriftCerebral Cortex
Nummer van het tijdschrift10
StatusGepubliceerd - okt. 2015


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