Synaptic Transmission Is Delayed During NREM Sleep Compared to Awake State in the Mouse Hippocampal CA1 Commissural Pathway.
The hippocampus is essential for spatial learning and memory, and sleep plays a major role in memory processing. In this study, using in vivo electrophysiological methods, we characterize the latency of hippocampal CA1 field Excitatory Postsynaptic Potentials (fEPSP) response. Then, we compared the latency during Non-rapid eye movement (NREM) sleep and the awake state during the period after fear-conditioning learning. We observed that after learning, the synaptic response during NREM state was delayed by about 0.3 ms compared to awake state. These results suggest that the speed of synaptic transmission is different between the NREM and the awake state. This effect could potentially come from the differences in neurochemical composition of the CA1 region during the NREM and the awake state.