Dysfunctional nurturing behavior in rat dams with limited access to nesting material: A clinically relevant model for early-life stress

Abstract

Limiting dams' ability to construct a nest for their pups leads to an abnormal repertoire of nurturing behaviors, possibly as a result of chronic stress and mild anxiety of the dams. Because the fragmented and aberrant maternal behavior provoked chronic stress in the pups, the limited-nesting paradigm provides a useful tool for studying the mechanisms and consequences of such early-life stress experience in the offspring.

Chronic Early-life Stress in Rat Pups Alters Basal Corticosterone, Intestinal Permeability, and Fecal Microbiota at Weaning: Influence of Sex

“…Exposure to early-life stress events has been reported to have a long lasting effect on HPA axis activity in adult rodents previously exposed to repeated maternal separation 22 and in adult humans. 33,34 The present results indicate that rat pups exposed to the LNS post-natal stress associated with altered maternal behavior 9,12,14 induces a basal state of elevated corticosteronemia which can be detected at weaning more prominently in females while not present at PND10. 14 This shows for the first time the onset of sex differences in a component of the HPA axis induced by early-life adverse environmental factors.…”

“…[3][4][5][6] Another model of early-life adverse events is the rearing of pups by dams subjected postpartum to conditions of limited bedding and nesting stress. 7,8 This model has face validity in humans 7,8 where the mother is continuously present but provides an altered repertoire of maternal behaviors indicative of fragmented and erratic care 9 and altered dam-pup interactions. 10 It has also the advantage of minimizing variability linked to handling of the pups to perform daily maternal separation.…”

Influence of housing variables on the development of stress-sensitive behaviors in the rat

“…Rats reared (and subsequently housed) on corncob bedding exhibited signicantly less-anxious phenotypes compared to those reared (then housed) on wood pulp bedding material. As glucocorticoid receptor, BDNF, CRH, CRH-R1, and CRH-R2 expression (in various neuronal regions) have all been implicated in the expression of fear and anxiety and are sensitive to early life environmental factors, we wished to assess if bedding conditions during early life inuenced the expression of these genes [11,31,[41][42][43]. Hypothalamic CRH, CRH-R1, and CRH-R2 mRNA levels were not signicantly different across conditions.…”

“…Rat dams themselves, with restricted access to bedding material during the postpartum period, also display an increase in HPA reactivity, more stressful behavioral phenotypes and altered hypothalamic CRH expression suggesting that environmental alterations increase maternal stress. While offspring behavior was not reported [31], other studies in which pups whose mothers were given restricted access to nesting and bedding material had decits in spatial memory, reduced body mass, and an increase in depressive-like behavior that were accompanied by changes in hippocampal CA1 long term potentiation [5].…”

“…Manipulation of the physical environment, including access to nesting sites and bedding, perturbs parental care which subsequently inuences neuroendocrine and behavioral phenotypes of developing offspring. For example, rat mothers with restricted access to bedding material during the postpartum period displayed more disorganized/ fragmented levels of maternal care than controls [31]. Rat dams themselves, with restricted access to bedding material during the postpartum period, also display an increase in HPA reactivity, more stressful behavioral phenotypes and altered hypothalamic CRH expression suggesting that environmental alterations increase maternal stress.…”