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Maternal Programming of Defensive Responses 163coeruleus, and almost nowhere else in the corticolimbic system (Caldji et al., 2003).Such effects may well represent a developmental strategy that permits phenotypicplasticity in response to early environmental conditions. Although such effectsmay be adaptive with respect to survival and reproduction, the cost of enhanceddefensive responses may be reflected in an increased risk for multiple forms ofchronic illness over the life span.ConclusionsWe have described what appears to be a sustained change in gene expression thatreflects variation in maternal care. So the obvious biological question is, whybother? As suggested earlier, we think that maternal effects represent a developmentalstrategy whereby the defensive responses of the offspring are refined inresponse to the prevailing level of environmental demand. In mammals, the relevantsignal that predicts the level of environmental demand is the behavior ofthe parent. Indeed, we use the term “developmental strategy” here more in a descriptivesense because the strategy may be seen as emerging from a strategy onthe part of the offspring (i.e., use the signals of the parent to forecast environmentaldemand) or the parent (i.e., signal the offspring in a manner that influences thedevelopment of defensive responses; see Wells, 2003). These need not be consideredas mutually exclusive options. The crucial assumption is that the result conferssome advantage onto the offspring with respect to survival and reproduction.Thus we propose that adversity in mammals alters parent-offspring interactionsin a manner that is designed to increase endocrine, cognitive, and emotional responsesto stress. In the rat, gestational stress is associated with decreased maternallicking/grooming (Champagne et al., 2001; Smith et al., 2004) and increasedstress reactivity in the offspring (Champagne et al., submitted). In the macaque,stress imposed on lactating females decreases the quality of mother-infant interactions(Rosenblum & Andrews, 1994) and increases endocrine and behavioralresponses to stress (Coplan et al., 1996, 1998). In the rat, decreased maternallicking/grooming is associated with increased fearfulness, enhanced HPA responsesto stress, and impaired performance on attentional tasks and tests of declarativelearning/memory under stressful conditions. These effects appear to bemediated by maternal effects on gene expression in relevant brain regions. Wesuggest that such effects produce an increased “preparedness” of defensive systems.Considering the adaptive value of behavioral and endocrine responses tostress, such a bias may be functional for an individual under conditions of increasedadversity. If this is the case, then we are better to consider functional differencesin developmental outcomes under conditions of adversity as reflecting alternativephenotypes, as opposed to impairments in development. Finally, althoughthese studies certainly support efforts to consider parental care as a relevant and