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Packard, B. A.

Publications and source records attributed to Packard, B. A..

2 recordsLinked to original sources

Selective modulation of the glucocorticoid receptor with CORT108297 during chronic adolescent stress evokes sex specific effects in adulthood.

Adolescent animals are vulnerable to the effects of stress on brain development. We hypothesized that long-term effects of adolescent chronic stress are mediated by glucocorticoid receptor (GR) signaling. We used a specific GR modulator (CORT108297) to pharmacologically disrupt GR signaling in adolescent rats during exposure chronic variable stress (CVS). Male and female rats received 30mg/kg of drug concomitantly with a 2-week CVS protocol starting at PND46. Emotional reactivity (open field) and coping behaviors (forced swim test (FST)) were then tested in adulthood, 5 weeks after the end of the CVS protocol. Blood samples were collected two days before FST and serial samples after the onset of the swim test to determine baseline and stress response levels of HPA hormones respectively.\n\nOur results support differential behavioral, physiological and stress circuit reactivity to adolescent chronic stress exposure in males vs. females, with variable involvement of GR signaling. In response to adolescent stress, males had heightened reactivity to novelty and exhibited marked reduction in neuronal excitation following swim stress in adulthood, whereas females developed a passive coping strategy and enhanced HPA axis stress reactivity. Only the latter effect was attenuated by treatment with the GR modulator C108297. Our data suggest that adolescent stress differentially affects emotional behavior and circuit development in females, and that GR plays a role in driving some but not all sequelae of adolescent stress.

neuroscience

Use of CRISPR/Cas9 Gene Targeting to Conditionally Delete Glucocorticoid Receptors in Rat Brain

Glucocorticoid receptors (GR) have diverse functions relevant to maintenance of homeostasis and adaptation to environmental challenges. Understanding the importance of tissue-specific GR function in physiology and behavior has been hampered by near-ubiquitous localization in brain and body. Here we use CRISPR/Cas9 gene editing to create a conditional GR knockout in Sprague Dawley rats. To test the impact of cell-and region-specific GR deletion on physiology and behavior, we targeted GR knockout to output neurons of the prelimbic cortex. Prelimbic deletion of GR in females caused deficits in acquisition and extinction of fear memory during auditory fear conditioning, whereas males exhibit enhanced active-coping behavior during forced swim. Our data support the utility of this conditional knockout rat to afford high-precision deletion of GR across a variety of contexts, ranging from neuronal depletion to circuit-wide manipulations, leveraging the behavioral tractability and enhanced brain size of the rat as a model organism.

neuroscience