Early experience as a determinant of adult behavioural responses to reward: the effects of repeated maternal separation in the rat.

Depression is a major public health concern, representing one of the most significant causes of disability and morbidity. Despite significant advances in the definition of specific cognitive, emotional and neural dysfunctions that are associated with depression, there has been frustratingly little progress in the elucidation of plausible aetiological and pathophysiological mechanisms. The complex, multi-system dysfunctions of depressive illness do not lend themselves to hypothesis-driven, systematic manipulation in patients. For this reason, there is a need to develop valid and reliable models of affective psychopathology in laboratory animals. In this paper, we review briefly some of our previous work demonstrating that a specific periodic neonatal maternal separation procedure leads to a robust constellation of behavioural changes in the adult rat that resemble core aspects of human depressive psychopathology. We also present data from a study of the adult effects of the same manipulation on electrical intracranial self-stimulation behaviour. These data further support the hypothesis that it is possible to model vulnerability to anhedonia in the adult rat by manipulation of early experience.