Abstract

Social contacts play an important role in the development and survival of social animals. Social isolation (SI) at adolescence often induces abnormalities in many kinds of behaviors . This study assessed whether five weeks of continuous SI at adulthood could alter social behaviors and whether dorsal raphe nucleus (DR) to medial prefrontal cortex (mPFC) 5-HT neural projections were involved in this alteration in C57BL/6J adult male mice. The present study found that five weeks chronic social isolation (CSI) at adulthood increased mounting and sniffing behaviors in resident-intruder test, and lengthened duration staying in interaction zone of stranger cage in the three-chamber social preference test. CSI also reduced the release of 5-HT in the mPFC detected by 5-HT 1.0 sensor and measured by in vivo fiber photometry test. Meanwhile, the c-Fos expression indicated that CSI reduced the activity of serotonergic neurons. Chemogenetic activation of DR-mPFC 5-HTergic projection reduced sniffing of CSI mice in the resident-intruder test, but didn’t significantly affect mounting behavior. It also decreased the interaction time during the three-chamber social preference test. Thus, 5-HT neural projections from the DR to the mPFC are involved in changes of social exploration behaviors induced by CSI at adulthood.