The age-related increase in arborization of the apical tree of xCT+/+ mice -once again an event which was not seen in xCT−/− mice- was restricted to the mid-apical dendrites (stratum radiatum) where the CA1 neurons receive extensive glutamatergic input of the Shaffer collaterals, possibly representing a compensatory reaction induced by excitotoxic damage in the aged hippocampus, as described in ischemia [84]. This evidence concerns the gene SLC7A11 and ischemia.