Neuronal Architecture of the Hippocampus and the Cerebral Cortex in Rats Experiencing Maternal Social Separation

Objective：Maternal social separation (MSS), a crucial early life experience, plays an essential role in the development of the nervous system. In our previous study, we demonstrated that the volume of the dentate gyrus decreases among rats experiencing MSS. Furthermore, chronic stress has been assumed to alter synaptic structures within the hippocampus. Therefore, we assessed the effects of MSS on neuronal morphology in the hippocampus and cerebral cortex. Methods：Golgi histochemistry and calretinin immunohistochemistry were used to evaluate the structure of neurons from the hippocampus and cerebral cortex in control and MSS rats. Results：Three weeks of maternal social separation was associated with morphological alteration of the apical dendrites of CA3 pyramidal neurons. Furthermore, calretinin-positive dentate pyramidal basket cells, GABAergic interneurons, significantly decreased in MSS rats. However, no morphological alterations of pyramidal neurons and interneurons in the cerebral cortex were observed. In addition, spine density in the terminal dendritic branches did not differ between control and MSS rats. Conclusion：These findings demonstrate that maternal social separation is associated with changes in neuronal architecture, and with biological features that might underlie behavioral and learning impairments.