Effects of different social interactions on hippocampal neurogenesis and neuron numbers in juvenile rats: a histological and behavioral study

Abstract

Purpose: Adolescence is a period of development affected by numerous hormonal and neurochemical changes. During this period, time spent with peers and experiences are known to have neurodevelopmental benefits. The hippocampus is a brain region where the production of new neurons after birth continues throughout life and is sensitive to changing social interactions. In this study, we aimed to investigate the effects of changing social interactions on behavioral parameters, doublecortin (DCX) expression, and total neuron numbers in the hippocampus of rat pups. Materials and methods: 21-day-old male and female Wistar albino rats were divided into three groups: control, social isolation, and environmental enrichment. Social isolation and environmental enrichment were applied for 4 weeks. Behavioral parameters were analyzed using ball burying, social interaction, and open-field tests. Following the behavioral tests, the rats were euthanized, and their hippocampal tissues were extracted. Cresyl violet staining was performed on paraffin sections, and DCX immunohistochemistry was performed on floating sections. Results: Increased social interactions had positive effects on exploratory behavior in adolescent rats. Decreased social interactions caused anxiety, depression behaviors, and increased locomotor activity. Histological analysis revealed a significant increase in the total number of neurons and DCX-positive neuroblasts in the dentate gyrus in the environmental enrichment group. In the social isolation group, a significant decrease in the total number of neurons and DCX-positive neuroblasts was observed. Conclusion: These results implied that changing social interactions during the weaning period have an effect on neurogenesis and the number of mature neurons in the DG, and this effect is regulated by different survival mechanisms.