Hyperlocomotor activity and stress vulnerability during adulthood induced by social isolation after early weaning are prevented by voluntary running exercise before normal weaning period

摘要

In rodents, the disruption of social-rearing conditions before normal weaning induces emotional behavioral abnormalities, such as anxiety, motor activity dysregulation, and stress vulnerability. The beneficial effects of exercise after normal weaning on emotional regulation have been well documented. However, effects of exercise before normal weaning on emotion have not been reported. We examined whether voluntary wheel running (R) during social isolation after early weaning(early weaning/isolation; El) from postnatal day (PD) 14-30 could prevent El-induced emotional behavioral abnormalities in Sprague-Dawley rats. Compared with control rats reared with their dam and siblings until PD30, rats performed R during El (El + R) and El rats demonstrated greater locomotion and lower grooming activity in the open-field test (OFT) during the juvenile period. Juvenile El ± R rats showed greater learned helplessness (LH) after exposure to inescapable stress (IS; electric foot shock) than IS-exposed control and El rats. In contrast, El rats showed increased locomotion in the OFT and LH after exposure to IS compared with control rats during adulthood; this was not observed in El ± R rats. Both El and El ± R rats exhibited greater rearing activity in the OFT than controls during adulthood. El did not increase anxiety in the OFT and elevated plus-maze. These results suggested that R during El until normal weaning prevented some of the El-induced behavioral-abnormalities, including hyperlocomotor activity and greater LH, during adulthood but not in the juvenile period.