Our aim is to understand the neural circuit underlying the cognitive control over the mal-adaptive behaviors that stem from stress-induced anxiety, especially among female adolescents. We also aim to understand why adolescent females are more vulnerable than males, adults and children to mental illnesses that are co-morbid with anxiety disorders. We have shown that adolescent female rodents that are exposed to the stress of food restriction (FR) exhibit individual differences in vulnerability to an anxiety disorer-like behavior, consisting of abnormality on the elevated plus maze, voluntary food restriction and excessive exercise, the latter of which contribute to severe weight loss and for some, death. This compilation of FR-evoked abnormalities, called activity-based anorexia (ABA) differs widely among individuals and correlate strongly with changes in the GABAergic inhibitory system (axons and alpha4betadelta-GABA receptors) in the prefrontal cortex and hippocampus. What remains unknown is whether the behavioral and anatomical changes are causally linked and if so, the mechanism for the stress (in this study, FR)-evoked up-regulation of the GABAergic system that protects animals from the mal-adaptive behavior. We hypothesize that (1) up-regulation to the GABAergic system of the prefrontal cortex and hippocampus is causal to the animal's ability to make decisions regarding responses to stressful environments (e.g., to eat or to run) that are more adaptive and to regulate the stress-evoked anxiety; and (2) individual differences in the GABAergic system of the prefrontal cortex and hippocampus arise from gonadal hormone fluctuations at puberty and the activity-dependent BDNF release. We will test these hypotheses by (1) determining the extent to which experimentally boosting the GABA system in the hippocampus and prefrontal cortex reduces ABA vulnerability and trait anxiety; and (2) determining whether systemic progesterone or the systemic or local alterations of BDNF level increase the strength of the GABA system and with it, reductions in the mal-adaptive behavior of voluntary FR, excessive exercise, and anxiety measures on the elevated plus maze. These goals will be achieved by quantifying the mal-adaptive behaviors of mice that are globally or locally knocked down of or boosted of the expression of GABAR subunits or of the GABA synthesizing enzyme or of BDNF and verifying the ultrastructure of GABAergic synapses by electron microscopy.
We will identify the cellular and molecular basis for individual differences in the cognitive control over mal-adaptive behaviors that are evoked by anxiety and stress during adolescence, and especially among females. These findings will help build design treatments of mental illnesses with comorbidity of anxiety disorders.
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