Effect of prenatal stress on neural oscillations in developing hippocampal formation.

The effect of prenatal stress (PS) on offspring's behavior was reported previously. Several studies attempted to reveal the mechanisms of PS on synaptic and molecular levels. However, the influences of PS on neural oscillations and their interaction in hippocampus are still unknown. In the present study, a PS rat model was established by using restraint stress. The local-field potentials (LFPs) were simultaneously recorded from the hippocampal CA3 and CA1 regions in young, adolescent and early-adult offspring rats. After that, LFPs were analyzed by analytic algorithms for estimating power spectrum, coherence, phase synchronization and cross-frequency coupling. The results showed that there was a significant influence of PS on power distribution from 1 to 100 Hz during different developmental stages. The identical-frequency synchronizations between CA3 and CA1 regions, including coherence and phase synchronization, were significantly reduced in PS rats compared to that in normal rats. Meanwhile, PS significantly impaired the cross-frequency coupling strength between theta and gamma rhythms. These data show that PS alters the neural oscillations and their interaction on the hippocampal CA3-CA1 pathway, which may be associated with the behavior outcomes and synaptic impairments previously reported in PS offspring rats. Moreover, the significant PS × age interactions between the effects of PS and age have been only found in the cross-frequency coupling, implying that the cross-frequency coupling more appropriately reflects the differences of the behavioral effects of PS in different postnatal ages.