Sex-dependent effects of an early life treatment in rats that increases maternal care: vulnerability or resilience?

Abstract

Early life stress (ELS) in rodents has profound long-term effects that are partially mediated by changes in maternal care. ELS not only induces “detrimental” effects in adulthood, increasing psychopathology, but also promotes resilience to further stressors. In Long-Evans rats, we evaluated a combination of two procedures as a model of ELS: restriction of bedding during the first post-natal days and exposure to a “substitute” mother. The maternal care of biological and “substitute” mothers was measured. The male and female offspring were evaluated during adulthood in several contexts. Anxiety was measured by the elevated plus-maze (EPM), acoustic startle response (ASR) and forced swim test (FST). In other group of animals, novelty-seeking was measured (activity in an inescapable novel environment, preference for novel environments and exploration of novel objects). Plasmatic ACTH and corticosterone in basal conditions and in response to stress were also measured. Cognitive impulsivity was assessed by a delay-discounting paradigm, and impulsive action, attention and compulsive-like behavior by a five choice serial reaction time task (5CSRTT). ELS decreased pup body weight and increased the care of the biological mother; however, the “substitute” mother did not exhibit overt maltreatment. A mixture of “detrimental” and “beneficial” effects was shown. In the 5CSRTT, attention was impaired in both genders, and in females, ELS increased compulsive-like behavior. Novel object exploration was only increased by ELS in males, but the preference for novel spaces decreased in both genders. Baseline anxiety (EPM and ASR) and recognition memory were not affected. Unexpectedly, ELS decreased the ACTH response to novelty and swim stress and increased active coping in the FST in both genders. Cognitive impulsivity was decreased only in females, but impulsive action was not affected. The enhancement in maternal care may “buffer” the effects of ELS in a context-dependent manner.

Sex differences in the behavioural and hypothalamic–pituitary–adrenal response to contextual fear conditioning in rats

“…Our data are in line with previous studies from our lab (Fuentes et al, 2014;Peña et al, 2009) and with most previous reports measuring basal plasma corticosterone (e.g. Patchev et al, 1999;Rhodes et al, 2002;Seale et al, 2004a).…”

Maternal separation induces neuroinflammation and long-lasting emotional alterations in mice

“…However, increased maternal care failed to recover MSEW-related impairment of neurobiological functions and behaviours during adolescence, like locomotion deficits, responses to stress and the manifestation of anhedonia related to a lack of preference for saccharine. We found that several of these alterations were more striking in females, reflecting their greater vulnerability to stress, as previous reported (Becker et al, 2007;Fuentes et al, 2014).…”

“…Experimental and clinical studies have shown that the immaturity and plasticity of the central nervous system during childhood make it particularly sensitive to stress at a young age, which may cause significant changes in brain structure and function (Lupien et al, 2009). In recent years, various rodent behavioural models of early life stress, such as maternal separation, have been used to study the neurobiological basis of emotional and motivational disorders (Fuentes et al, 2014;Martini and Valverde, 2012;Pryce et al, 2001aPryce et al, , 2001b. Maternal separation with early weaning (MSEW) (George et al, 2010) attempts to reduce any potential compensatory maternal care after maternal deprivation.…”

Gambling in rhesus macaques (Macaca mulatta): The effect of cues signaling risky choice outcomes

“…Beyond appearances, however, there are reasons to believe that the signaling effect captures a psychologically meaningful aspect embedded in the traditional gambling environment. First, the neurological basis for gambling disorders may be based in reward anticipation (e.g., Linnet, 2014) and the signaled-delay procedure accentuates that aspect of the risky choice contingency. Second, this task has shown promise as a means to predict individuals with a gambling habit.…”