Early-life social experiences in mice affect emotional behaviour and hypothalamic-pituitary-adrenal axis function.
BACKGROUND
Early-life stressful experiences are associated to alterations in behavioural responses and development of psychiatric and neurodegenerative diseases. In rodents, individual housing is considered as a stressful condition whilst enriched environment can protect against stress and its negative consequences. Neuroendocrine responses to stress can also be altered by early-life experiences and seem to contribute to behavioural alterations induced by changes in housing conditions.


OBJECTIVE
To develop an improved procedure of social isolation throughout development (from pre-adolescence to adulthood) in CD1 mice and to elucidate its effects on behavioural parameters related to stress and neuroendocrine responses compared to enriched or social conditions.


METHODS
CD1 male mice (PND 21) were housed in social/standard conditions, enriched conditions or isolated conditions during seven weeks. After that, different relevant behaviours were evaluated, including locomotor activity, anxiety-like and despair behaviour. Levels of plasma corticosterone were also analysed before and after a stressful event.


RESULTS
CD1 mice exposed to an isolated environment exhibited higher locomotion and anxiety-like responses than animals exposed to social or enriched conditions. In addition, isolated animals showed lower basal plasma corticosterone than social or enriched ones but after a stressful event the elevation of plasma corticosterone was higher, suggesting an enhanced response of the HPA axis to a novel and stressful situation.


CONCLUSIONS
Social interaction is an important feature to display an appropriate behavioural and neuronal development. Habituation to novel stimuli is impaired in subjects exposed to social isolation and induces increased excitability response to stressful events. Social deprivation increases the possibility of altered neuronal function and could facilitate the development of neuropsychiatric disorders in adulthood.
Grup de Recerca en Neurobiologia del Comportament-GReNeC, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, Parc de Recerca Biomèdica de Barcelona, Dr Aiguader 88, 08003 Barcelona, Spain.
Clara
C
Ros-Simó
Olga
O
Valverde
D000704:Analysis of Variance; D000818:Animals; D001007:Anxiety / Q000523:psychology; D001522:Behavior, Animal / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D003345:Corticosterone / Q000097:blood; D004644:Emotions / Q000502:physiology*; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000502:physiology; D010913:Pituitary-Adrenal System / Q000502:physiology*; D012931:Social Environment; D012934:Social Isolation / Q000523:psychology; D013315:Stress, Psychological / Q000097:blood / Q000523:psychology
D003345:Corticosterone