Developmental Changes in Early Sharp Waves in the Hippocampus of Neonatal Rats

Synchronized activity the hallmark of neural networks. Early sharp waves (eSPW) form one type of synchronized activity – these are synchronized network discharges of neuronal ensembles seen in the developing hippocampus. Despite the fact that eSPW may play a central role in coordinating neural activity and forming hippocampal functions, little is known of changes in eSPW during early postnatal development. Our experiments on neonatal rat pups using multichannel extracellular electrodes showed that during the first two weeks of postnatal life, along with reductions in the duration of eSPW, there were increases in their frequency and amplitude. We also found an increase in extracellular recorded activity of neurons in the pyramidal layer of the hippocampus. These data lead to the suggestion that the dynamics of changes in eSPW and overall network hippocampal activity are associated with the development of the hippocampal neural network and bottom-up neuromodulator projections.