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Front. Behav. Neurosci. | doi: 10.3389/fnbeh.2018.00287

Loss of Environmental Enrichment Elicits Behavioral and Physiological Dysregulation in Female Rats

Rachel Morano1, Olivia Hoskins1, Brittany L. Smith1 and  James P. Herman1*
  • 1Pharmacology and Systems Physiology, University of Cincinnati, United States

Chronic stress drives behavioral and physiological changes associated with numerous psychiatric disease states. In rodents, the vast majority of chronic stress models involve imposition of external stressors, whereas in humans stress is often driven by internal cues, commonly associated with a sense of loss. We previously exposed groups of rats to environmental enrichment (EE) for a protracted period (one month), followed by removal of enrichment (ER), to induce an experience of loss in male rats. ER enhanced immobility in the forced swim test (FST), led to hypothalamic pituitary adrenal (HPA) axis hypoactivity, and caused hyperphagia relative to continuously enriched (EE), single-housed (Scon) and pair-housed (Pcon) groups, most of which were reversible by antidepressant treatment [1]. Here, we have applied the same approach to study enrichment loss in female rats. Similar to the males, enrichment removal in females led to an increase in the time spent immobile in the forced swim test and increased daytime food intake compared to the single and pair-housed controls. Unlike males, ER females showed decreased sucrose preference, and showed estrus cycle-dependent HPA axis hyperactivity to an acute restraint stress. The increase in passive coping (immobility), anhedonia-like behavior in the sucrose preference test and HPA axis dysregulation suggest that enrichment removal produces a loss phenotype in females that differs from that seen in males, which may be more pronounced in nature.

Keywords: Anhedonia, coping behavior, Corticosterone, estrus cycle, sex differences, stress

Received: 13 Jul 2018; Accepted: 06 Nov 2018.

Edited by:

Amanda C. Kentner, MCPHS University, United States

Reviewed by:

Marie-Claude Audet, University of Ottawa, Canada
Kelly Lambert, University of Richmond, United States
Tara S. Perrot, Dalhousie University, Canada  

Copyright: © 2018 Morano, Hoskins, Smith and Herman. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. James P. Herman, University of Cincinnati, Pharmacology and Systems Physiology, Cincinnati, 45208, Ohio, United States, jpherman87@gmail.com