Forebrain Glucocorticoid Receptor Overexpression Increases Environmental Reactivity and Produces a Stress-Induced Spatial Discrimination Deficit

Abstract

Reactivity to environmental stressors influences vulnerability to neurological and psychiatric illnesses, but little is known about molecular mechanisms that control this reactivity. Since mice with forebrain-specific glucocorticoid receptor overexpression (GRov mice) display anxiety-like behaviors in novel environments and have difficulty adjusting to change in memory tasks, we hypothesized that these may be facets of a broader phenotype of altered reactivity to environmental demands. Male GRov and wild-type mice were tested in a multiple-trial object interaction test comprising environmental and object habituation and spatial and object novelty trials. Half the mice received restraint stress before testing. GRov mice exhibited more locomotor activity and, without stress, more object interaction than wild-type mice. Following acute stress, GRov mice no longer showed increased object exploration. While stress dampened responses to object novelty in both groups, GRov mice were particularly impaired in discrimination of spatial novelty poststress. These data demonstrate that GRov leads to increased environmental reactivity, responsiveness to salience, and vulnerability to stress-induced cognitive deficits. They implicate forebrain glucocorticoid receptor (GR) in fine-tuning interactions with the environment and the interplay of emotional salience, coping abilities, and cognitive function.