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Effect of Chronic Stress Exposure on Beta-Adrenergic Receptor Signaling and Fear- Learning

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Effect of Chronic Stress Exposure on Beta-Adrenergic Receptor Signaling and Fear- Learning Effect of Chronic Stress Exposure on Beta-adrenergic Receptor Signaling and Fear- Learning A dissertation submitted to Kent State University in partial fulfillment of the requirements for the degree of Doctor of Philosophy By Robert Michael Camp June 2015 © Copyright All rights reserved Except for previously published materials Dissertation written by Robert M. Camp B.A. Kent State University, 2009 Ph.D. Kent State University, 2015 Approved by __________________________________________________ Dr. John D. Johnson, Advisor, Department of Biological Sciences __________________________________________________ Dr. Eric M. Mintz, Member, Department of Biological Sciences __________________________________________________ Dr. Heather K. Caldwell, Member, Department of Biological Sciences __________________________________________________ Dr. Aaron M. Jasnow, Outside member, Department of Psychology __________________________________________________ Dr. David C. Riccio, Graduate faculty representative, Department of Psychology Accepted by __________________________________________________ Dr. Laura G. Leff, Chair, Department of Biological Sciences __________________________________________________ Dr. James L. Blank, Dean, College of Arts & Sciences ii Table of Contents Page List of Figures………………………………………………………………………………….viii List of Abbreviations…………………………………………………………………………….x Acknowledgements…………………………………………………………………………….xii Chapter I. Introduction………………………………………………………………………….1 Stress, defined…………………………………………………………………………..1 Stress and psychological disorder…………………………………………………….2 Selye and the GAS, Cannon and “Fight-or-Flight”.................................................5 The neuroendocrine stress response………………………………………………...7 The central stress response………………………………………………………….11 Memory, stress, and norepinephrine………………………………………………...14 Repeated stress alters noradrenergic signaling……………………………………16 Focus of dissertation…………………………………………………………………..17 Chapter II. Strain- and context-dependent effects of repeated stressor exposure on the expression of depressive-like behavior in rats……………………………………………..22 Introduction…………………………………………………………………………….22 Methods and procedures……………………………………………………………..25 Subjects..……………………………………………………………………….25 Drug delivery…………………………………………………………………...26 Repeated stress protocol……………………………………………………..27 Sucrose preference measurements………………………………………....28 iii Behavioral measurements…………………………………………………....28 Organ weight and stress hormone measurement………………………….29 Statistical analysis……………………………………………………………..30 Study 1: effects of context on behavioral changes in animals exposed to chronic stress……………………………………………………………….….30 Study 2: the role of β-ARs in enhanced contextual fear conditioning in chronically stressed animals………………………………………………....30 Study 3: differential effects of chronic stress between central and peripheral β-ARs……………………………………………………………....31 Study 4: disparity between laboratory rat strains in effects of chronic mild stress exposure..………………………………………………………………31 Results………………………………………………………………………………….32 Study 1: effect of context on repeated stress-induced behavioral changes………………………………………………………………………...32 Study 2: effect of propranolol on repeated stress-induced behavioral changes………………………………………………………………………...37 Study 2: effect of propranolol on stress-induced changes in body and organ weights..………………………………………………………………...43 Study 2: effect of propranolol on corticosterone levels following acute and repeated stressor exposure………………………………………………….46 Study 3: effect of nadolol on repeated stress-induced behavioral changes………………………………………………………………………...49 iv Study 3: effect of nadolol on spleen weight following repeated stressor exposure…...…………………………………………………………………...54 Study 4: effects of repeated stress-induced behavioral changes in Sprague-Dawley rats….……………………………………………………….54 Discussion………………………………………………………………………………58 Conclusion……………………………………………………………………………...62 Chapter III: Repeated stressor exposure enhances contextual fear memory in a beta- adrenergic receptor-dependent process and increases impulsivity in a non-beta receptor-dependent fashion...………………………………………………………………...64 Introduction……………………………………………………………………………..64 Methods and materials…….…………………………………………………………..66 Subjects…………………………………………………………………………66 Repeated stress protocol……………………………………………………...67 Behavioral testing………………………………………………………………68 Conditioned fear………………………………………………………..68 Open field...……………………………………………………………..69 Passive avoidance….………………………………………………….69 Beta-adrenergic receptor antagonist administration……………………….70 Statistical analysis……………………………………………………………..70 Experimental design…………………………………………………………..70 Results………………………………………………………………………………….71 Effect of CMS on freezing behavior………………………………………….71 v Effect of CMS on passive avoidance behavior……………………………..74 Effect of repeated stress on non-contextual anxiety-like behavior……….74 Discussion……………………………………………………………………………...76 Chapter IV: Effects of chronic mild stress on sensitization of beta-adrenergic receptor- stimulated intracellular signaling in amygdaloid and hippocampal tissue……………….80 Introduction……………………………………………………………………………..80 Methods and procedures……………………………………………………………...83 Subjects…………………………………………………………………………83 Chronic mild stress protocol……...…………………………………………...83 Beta-adrenergic receptor stimulation………………………………………...83 Cellular signaling analysis…………………………………………………….84 Statistical analysis……………………………………………………………..84 Experimental design………………………………………………….………..85 Results……………………………………………………………………….………….85 Effect of stress and propranolol on intracellular signaling in the amygdala……………………………………………………………………….85 Effect of propranolol on intracellular signaling on intracellular signaling in the hippocampus……………………………………………………………….89 Discussion………………………………………………………………………………92 Chapter V: Global discussion………………………………………………………………...95 Future directions……………………………………………………………………...103 Final thoughts…………………………………………………………………………105 vi References……………………………………………………………………………………107 vii List of figures Page Chapter I. Introduction Fig. 1. The HPA axis and the sympathetic nervous system………………………………..8 Fig. 2. Hypothetical process of stress-induced enhancement of fear memory…………18 Fig. 3. Intracellular signaling at β-ARs………………………………………………………21 Chapter II. Strain- and context-dependent effects of repeated stressor exposure on the expression of depressive-like behavior in rats Fig. 4. Effects of context on behaviors following repeated stressor exposure………….33 Fig. 5. Effects of chronic propranolol infusion on behaviors following repeated stressor exposure………………………………………………………………………………………..38 Fig. 6. Effects of chronic propranolol infusion and repeated stressor exposure on body and organ weights……………………………………………………………………………..44 Fig. 7. Effects of chronic propranolol infusion on corticosterone responses…………….47 Fig. 8. Effects of chronic nadolol infusion on behaviors following repeated stressor exposure………………………………………………………………………………………..50 Fig. 9. Effect of chronic nadolol infusion and repeated stressor exposure on spleen weight…………………………………………………………………………………………...55 Fig. 10. Behavioral effects of repeated stressor exposure in Sprague-Dawley rats.…..56 Chapter III: Repeated stressor exposure enhances contextual fear memory in a beta- adrenergic receptor-dependent process and increases impulsivity in a non-beta viii receptor-dependent fashion Fig. 11. Effects of chronic mild stress on contextual fear conditioning…………………..72 Fig. 12. Effects of chronic mild stress on latency in a passive avoidance test..….……..73 Fig. 13. Effects of chronic mild stress on open field behavior.……………………………75 Chapter IV. Effects of chronic mild stress on sensitization of beta-adrenergic receptor- stimulated intracellular signaling in amygdaloid and hippocampal tissue Fig. 14. Effects on intracellular signaling in the amygdala following repeated stressor exposure………………………………………………………………………………………..86 Fig. 15. Effects on intracellular signaling in the hippocampus following repeated stressor exposure………………………………………………………………………………………..90 Chapter V. Global discussion Fig. 16. Observed process of stress-induced enhancement of fear memory...…………96 Fig. 17. Additional components of signaling at β-ARs……………………………………102 ix List of abbreviations ACTH - adrenocorticotropic hormone AMPA(R) - α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (receptor) β-AR - beta-adrenergic receptor BDNF - brain-derived neurotrophic factor BLA - basolateral nucleus of the amygdala CAMK-IV - calmodulin kinase IV cAMP - 3’-5’-cyclic adenosine monophosphate CMS - chronic mild stress CORT - corticosterone or cortisol CREB - cAMP response element-binding CRH - corticotropin-releasing hormone DEX - dexamethasone EDTA - ethylenediaminetetraacetic acid ELISA - enzyme-linked immunosorbent assay ERK - extracellular signal-regulated kinase GAD - generalized anxiety disorder GAS - general adaptation syndrome GR – glucocorticoid receptor GluR1 - glutamate receptor 1 HCC – home cage controls HPA - hypothalamic-pituitary-adrenal x IL-1β - interleukin-1 beta IL-6 - interleukin-6 LC - locus cœruleus LTP - long-term potentiation MAPK - mitogen-activated protein kinase MHPG - 3-methoxy-4-hydroxyphenethylene glycol NE - norepinephrine NMDA - N-methyl-D-aspartate NTS - nucleus tractus solitarius or nucleus of the solitary tract PFC - prefrontal cortex PKA - protein kinase A PTSD - posttraumatic stress disorder RT-PCR - real-time polymerase chain reaction SNS - sympathetic nervous system TMT - trimethylthiazoline TNF-α - tumor necrosis factor
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