Does Salt Make You Scared? Evaluating How High Salt Intake in Mice Affects Anterior Cingulate Cortex GABA Signaling and Downstream Fear Behaviors

Abstract ID 90488 Poster Board 298 Anxiety disorders are the most frequent type of neuropsychiatric disorders, with a prevalence of around 30% in U.S. adults, and women are disproportionately more affected. A key symptom across anxiety disorders is pathological fear generalization. Fear generalization is typically an adaptive process, but can become maladaptive (i.e., pathological) when stimuli that are not harmful are perceived as threatening. Disruptions in GABAA receptor signaling have been implicated in anxiety disorders. GABAA receptors are abundant throughout the brain, including in the anterior cingulate cortex (ACC), a critical brain region for fear generalization. Typically, activation of GABAA receptors leads to neuronal inhibition. However, reversal of the chloride gradient (under certain conditions such as excess salt intake in male rats) reverses effects of GABA's activation of GABAA receptors, leading to neuronal excitation. A high salt diet also sex-specifically affects fear generalization in mice, where fear generalization is attenuated in males but augmented in females. Further, excess salt consumption has been associated with exacerbated anxiety symptoms in humans. To start understanding the underlying neurophysiology, we investigated how ACC chloride gradients were impacted by salt intake, and how GABAA receptor agonism in the ACC affected fear generalization. Given evidence that excess salt intake can reverse the chloride gradient in male rats, we hypothesized that this same reversal is contributing to sex-specific effects of high salt intake on fear generalization. To test this hypothesis, male and female C57BL/6J mice underwent context fear training two wks into a 6 wk diet manipulation using either control (0.4% NaCl, w/w) or high salt (4.0% NaCl) diet. Mice were tested 4 wks after training (thus, after 6 wks on diet) to examine fear generalization. Mice underwent stereotaxic surgeries at diet wk 5 (one week before context fear testing) to implant cannulae targeting the ACC. Then, just before testing at the 6 wk time point, mice underwent intracranial infusions of 0.25μL of either vehicle (PBS) or muscimol (0.5 μg; GABAA receptor agonist). Experiments and data analyses are ongoing, but results could bridge gaps in knowledge regarding how fear generalization becomes pathological in sex-specific and diet-dependent ways. Specifically, our investigations might help explain how consuming a high salt diet exacerbates some symptoms of anxiety disorders, and thereby identify a potentially novel complement to therapeutic approaches. Funding: This project was supported by an Applied Psychology Center Graduate Student Research Fellowship to JNB from Kent State University, and by a Farris Family Innovation Award to TLG.