Neonatal handling and environmental enrichment increase the expression of GAP-43 in the hippocampus and promote cognitive abilities in prenatally stressed rat offspring

Abstract

Neonatal handling and environmental enrichment have been used to aid the treatment and recovery of a diverse variety of brain dysfunctions. However, the underlying mechanism and the effects on cognitive function following neonatal handling and environmental enrichment are still unclear. In this study, we investigated GAP-43 protein levels in the hippocampus of prenatally stressed rat pups by Western blot on postnatal day (P) 10, P20 and P45. The cognitive ability of prenatally stressed rat pups was tested by using the Morris water maze on P45. GAP-43 protein levels were upregulated on P10 in the prenatal restraint stress (RS) group and the prenatal restraint stress plus neonatal handling and environmental enrichment (RE) group compared to the negative control (NC) group. However, the expression of GAP-43 in RS pups was lower on P20 and P45 than that in NC and RE pups. Exposure to prenatal stress prolonged average latency and total swim distance, but neonatal handling and environmental enrichment could reverse the change. Differences were also observed in the selection of search strategies. These results indicate that neonatal handling and environmental enrichment can improve the spatial learning and memory ability of prenatally stressed offspring, and the possible mechanism is the upregulation of GAP-43.