Brief maternal separation procedures occurring early in life affect learning and memory in adult Wistar rats: Sex-related differences in cognitive behaviour

Abstract

Adverse life events during the neonatal period result in long-term effects on physiology and behavior.1 Early postnatal experiences, such as a modification of the mother–infant interaction, may influence the development of neural systems that underlie the expression of neuroendocrine and behavioural responses to environmental challenges, involving changes in the hypothalamic-pituitary-adrenal (HPA) axis2 together with decreased levels of brain-derived eurotrophic factor (BDNF) and nerve growth factor (NGF).3 Disturbances in mother-infant interaction represent a natural stressor which may lead to maladaptive develop ment; indeed protracted Maternal Separation (MS) reduces maternal care thus induce in abnormal HPA axis responses, hippocampal BDNF down-regulation impaired memory formation The opposite is observed when maternal care is increased by a daily brief, maternal sep aration. The polymorphism of neuroendocrine processes and behaviour al responses following brief MS procedure 7 includes gender-related dif ferences; however very few studies exist on sex-specific behaviours.7 Based upon these findings, the present study was carried out to investi gate the consequences of a brief, maternal separation on declarative and spatial memory, focusing on sex related alteration due to the discrete effects that hormones may play on the brain