Since no increase in SR expression (but rather a decrease in SR expression was observed during the first 12 h of ischemic insult) or decrease in DAAO expression was observed in different models of ischemia, it is reasonable to suppose that increased levels of D-serine may result from increased SR activity (likely as a consequence of phosphorylation, changes in intracellular distribution, and/or change in binding partners), decreased DAAO activity, altered shuttling of D-serine across membranes, and or altered NR1 expression and sensitivity. Here, DAO is linked to ischemia.