It is well-known that sleep serves several functions, such as energy saving, detoxification, and brain temperature regulation. Recently, many sleep researchers are interested in the relationship between sleep and synaptic plasticity, and hypothesize that the synaptic connection becomes stronger during wakefulness and weaker during sleep. In order to confirm this hypothesis, we performed whole-cell patch-clamp recordings from layer II/III pyramidal neurons of somatosensory cortex in acute slices of the adolescent rats that had been awake or asleep. We found that current-voltage (I-V) relationship of EPSCs showed inward rectification in slices of both waking and sleep deprived animals, but I-V plots of EPSCs in sleeping rat were linear. In addition, we found that eEPSCs were depressed by Philanthotoxin 74 (PhTx), which is antagonist of Ca ²⁺ permeable AMPA receptors, in both waking and sleep deprived animals. In contrast, PhTx did not change EPSPs amplitude in sleeping rats. These results show that amount of Ca²⁺ permeable AMPA receptors, which plays a crucial role in synaptic potentiation, are expressed during wakefulness. These strongly suggest that synapses become widely potentiated during wakefulness.