Persistência versus esquecimento: efeitos da neurogênese adulta na memória social de camundongos C57BL/6J

Abstract

Adult neurogenesis is the process which new neurons are born in the adult brain. A role for adult-born neurons in mnemonic mechanisms has been revealed by studies that increase and/or decrease neurogenesis. Curiously, depending on when during memory processing the manipulation is done adult neurogenesis can favor as much persistence as forgetting. Social memory (SM) is the ability to remember conspecifics. Although SM is susceptible to adult neurogenesis changes, it is an open question if adult-born neurons play a role in SM persistence and forgetting like they do in other hippocampus-dependent memories. In the present study, we manipulate adult neurogenesis using enriched environment (EE), running wheels (RUN), antimitotic drug (TMZ) and chemogenetics (hM4Di). Neurogenesis was measured as doublecortin (DCX) and BrdU expression. SM was accessed by the social recognition task, which experimental mouse has two successive encounters with the same social stimulus (juvenile) and a decrease on social interaction during the second time is indicative of SM. Our results show that C57BL/6J mice are resistant to the pro- and anti- neurogenic effect of EE and TMZ, respectively. Even though SM persistence was mitigated by TMZ. Nevertheless, chemogenetic inactivation of adult-born neurons before SM acquisition impaired it, suggesting the activity of these cells is necessary for SM formation. Interestingly, the interaction with a juvenile reduced dorsal CA2 c-Fos expression and this region is known for its specific role in SM. Neurogenesis enhancement with RUN after SM acquisition caused its forgetting when the task was made difficult by reducing habituation duration. Overall, our results support a role for adult neurogenesis in SM persistence and forgetting. Adult-born neurons activity seems to be important for SM and the adult neurogenesis forgetting effect on SM appears to be different from what happens with other memories.