Systems neuroscienceDysfunctional nurturing behavior in rat dams with limited access to nesting material: A clinically relevant model for early-life stress
Section snippets
Animals
Sprague–Dawley timed-pregnant female rats (Zivic-Miller, Zelienople, PA, USA) were housed in the federally approved University of California, Irvine vivarium and maintained in quiet, temperature-controlled rooms on a 12 h light/dark cycle (6 pm lights off/6 am lights on) with access to unlimited laboratory chow and water. Parturition was verified at 12 h intervals (date of birth=day 0). On the second day of the pups' life (postpartum day (P) 2), litters were culled to 12 pups if necessary, and
Reduced nesting/bedding material provoked abnormal nurturing behaviors in the dams
Maternal licking and grooming of the pups have been extensively shown to be important parameters of nurturing behaviors associated with reduced stress responses of the offspring during adulthood (Liu et al 1997, Caldji et al 2000). Restricting the nesting material available to the ES dams prevented them from constructing adequate nests for their pups, and reduce the overall quality of their care, including licking and grooming activities. Comparing their behaviors to those of control dams, the
Discussion
The main findings of these studies are: (1) Limiting a dam's ability to nest provokes abnormal nurturing behaviors toward her offspring. (2) A key element of this abnormal maternal behavior involves its inconsistent and fragmented nature. (3) The dams' abnormal nurturing behaviors are associated with, and perhaps a result of, changes in physiological and psychological indicators of chronic stress; these include increased plasma corticosterone, hypertrophic adrenal glands, reduced hypothalamic
Conclusion
In summary, a model of dysfunctional maternal nurturing behaviors is described here, that it is based on limiting nesting material in the cage. The paradigm influences the quality as well as the quantity of the dams' nurturing activities, recapitulating an important element of human early-life neglect and abuse. Because a week of exposure to this disrupted maternal care leads to long-lasting effects on the offspring that resemble those in human survivors of early-life neglect/abuse (Bremner and
Acknowledgments
The authors acknowledge Natalie Korthamar for excellent technical assistance with the maternal behavioral analysis and Joy Calara for editorial contributions. Supported by NIH NS28912 and MH73136 (T.Z.B.).
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