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Stress
modelDescription Source CMS; CUS; CVS Originally developed by Paul Willner as a model for depression, involves the subjugation of animals to a series of multiple, unpredictable stressors over a prolonged period;
May vary in the combination and duration of stressors;
Many limitations, such as difficulty to replicateWillner, 1997;
Lezak et al., 2017CSDS Initially developed to model depression by Avgustinovich et al. (2005); was popularly adapted to investigate anxiety phenotypes by Krishnan et al. (2007);
Study animal is introduced to the cage of a larger, aggressive animal (often a different strain of rat or mouse);
Study animal is consider the “intruder”; aggressor animal is considered a “resident”;
Exposure lasts for 10 min for 10 d, but may differ based on the researcher’s goals;
Some animals may overcome CSDS-induced anxiety and are considered models for studying anxiety resilience;
Limitations: sex-related differences (females tend not to participate in territorial related aggression); and injury to the model animal by the aggressor animalAvgustinovich et al., 2005; Krishnan et al., 2007; Lezak et al., 2017 Prenatal stress Originally used in rats by William Thompson, this stress model involves the application of a stressor to a pregnant dam; later adapted to study anxiety-like behaviors in offspring by other researchers (Vallée et al., 1997);
Considered a developmental form of stress;
Stressors include, e.g., footshock, restraint stress, subjection to EDCs; for more comprehensive reading on variations used in this model, please refer to Weinstock (2017)Thompson et al., 1962;
Vallée et al., 1997;
Lezak et al., 2017Postnatal stress Administration of a stressor following the birth of pups and was first reportedly used by Krzysztof Janus (1987);
Considered a developmental form of early life stress;
The most commonly employed stressor is maternal separation in rodents, the time of separation is crucial for inducing anxiety-like phenotypes: separation at P3 to P4 tends to induce anxiety-like behaviors, while separation at P11 to P12 has been shown to cause the opposite effect of hyporesponsivenessMurthy and Gould, 2018; Lezak et al., 2017;
van Oers et al., 1998CUS, Chronic unpredictable stress; CVS, chronic variable stress; P, postnatal day.
Test Characteristics Source Light/dark box assay Box apparatus is divided into two sections: the smaller dark “protected” side (minimally lit with black walls), and the larger light ‘unprotected’ side (brightly illuminated with white walls);
Relies on the principle of the innate aversion of a rodent to light and exposure to predators as a prey animals;
Shorter latency periods entering the light side, and/or longer periods spent here, are interpreted as reduced anxiety-like behaviors;
Measures the approach–avoidance behaviorCrawley and Goodwin, 1980;
Campos et al., 2013;
Lezak et al., 2017EPM test Consists of two open, or unenclosed arms opposing two enclosed arms in the shape of a plus sign;
Apparatus is elevated several feet from the ground;
Animals are placed at the left of the EPM and allowed to explore freely for 5 min;
Exposure created by open arms is associated with anxiety-like behavior, such as increased defecation and corticosteroid levels;
More time spent in, as well as higher percentage of entries into the open arms of the EPM, are interpreted as reduced anxiety-like indices;
Measures approach–avoidance behaviorsHandley and Mithani, 1984;
Korte, 2001;
Campos et al., 2013;
Lezak et al., 2017Open field test Consists of an open box divided into layers of rings from the left of the box to the corners;
The time spent in the middle where hypothetically the animal is most exposed and vulnerable, is compared with the amount of time spent hugging the safer corners of the box;
The number of times ventured towards the left of the box is also recorded;
Reduced anxiety is inferred if the animal tends to venture out from peripheral zones, or spend longer periods in the more central zones of the open box;
Relies on instinctual fear responses to predatorsLezak et al., 2017 Protein product Gene denotation Glutamate receptor subunits Grik1, Grik2, Grin1, Grin2b, Grin3a, Grm5, Nr2b GABA receptor subunit Gabra2, Gabbr1, Gabbr2 Mineralocorticoid receptor Nr3c2 Glucocorticoid receptor Nr3c1 Jagged-1 JAG1 B-cell lymphoma/leukemia 11A Bcl11A Corticotropin-releasing hormone/corticotropin-releasing factor CRH/CRF Glutamic acid decarboxylase GAD67 CRH receptor Crhr1 FK506 binding protein 5 FKBP5 Histone-lysine N-methyltransferase SUV39H1 SUV39H1 Euchromatic histone-lysine N-methyltransferase EHMT2, G9a G9a-like protein EHMT1, GLP Marker Sample retrieved Anxiety model Reference ↕Dnmt1 Hippocampus (CA1, CA3)
Amygdala (medial, basolateral and lateral nucleus)bLR animals (rats: P7 to P14) Simmons et al., 2012 ↓Dnmt3a Peripheral blood Anxious young adults (measured with HADS-A) Murphy et al., 2015 mPFC Adult CSDS (9 weeks) mice (killed 4 weeks after CSDS) Elliott et al., 2016 ↓Dnmt3a
↓Dnmt3b ↓Grin2b ↓Gabar2 ↑Grin1Hippocampus Low-methyl diet adult mice (6 and 12 weeks) (low anxiety) Ishii et al., 2014 ↑NR3C11F (Me) Peripheral whole blood Adolescents (mean age = 16 years) who reported SLE's van der Knaap et al., 2014 ↓NR3C11F (Me) Leukocytic blood Adults (age range = 18–65 years) who reported SLEs and diagnosed with variable ADs Tyrka et al., 2016 ↑NR3C1 (Me)
↓GRαPBMCs Adults (mean age = 35 years) diagnosed with GAD Wang et al., 2017 ↓GR ↑FKBP5 Placenta NR3C1+/− mice Schmidt et al., 2019 ↑FKBP5 Amygdala Adult rats (25 weeks) born to dams exposed to predator odors (prenatal/in utero stress) St-Cyr et al., 2017 Amygdala (basolateral) Viral overexpression of FKBP51 Hartmann et al., 2015 ↓Dnmt1 ↑Gabra2
↓GABAWhole brain H67D male mutant mice (low anxiety) Ye et al., 2018 ↑Dnmt1 ↓GAD67 Amygdala (basolateral) Female mice (P45) exposed to BPA in utero Zhou et al., 2013 Female mice (P60/P70) exposed prenatally/in utero to maternal restraint stress Zhu et al., 2018 ↑Crf ↓Dnmt3b Hypothalamus (PVN) Adult CSDS mice Elliott et al., 2010 ↑Crf ↑Cortisol Hypothalamus PRS adolescent rats (P38) born to dams subjected to restraint stress Xu et al., 2014 ↑Crf ↑CRHR1,
↓Dnmt3bHypothalamus (PVN) Male adult (P90) rats exposed in utero to gestational hypoxia Wang et al., 2013 ↓CRHR1 (Me) Peripheral whole blood Adults (mean age = 35 years) diagnosed with panic disorder Schartner et al., 2017 ↑Crhr1 Amygdala (basolateral) HAB mice bred for a high anxiety trait, LAB mice exposed to CMS Sotnikov et al., 2014 GRIN1, GRM5
↓BCL11A, ↓JAG1Amygdala (central) Anxious temperament rhesus macaques (mean age = 1.3 years) Alisch et al., 2014 Genes are italicized. (me) denotes methylation reported. HADS-A, Hospital anxiety and depression scale; P, postnatal day.
- Table 5
Summary of differential histone modifications marks and histone modifying enzymes in stress/anxiety models
Marker Sample retrieved Stress model Reference ↑H4ac ↑BDNF IV Prefrontal cortex Footshock conditioned male mice (10–12 weeks) with fear extinction learning (low anxiety) Bredy et al., 2007 ↓H3K9me2 ↑BDNF IV Hippocampus Male rats (P21 and 2 months) subjected to maternal separation Suri et al., 2013 ↑H3K9me2 ↓BDNF IV Male rats (15 months) subjected to maternal separation ↓H3K9me ↓H3K9me3 Hippocampus Adult male rats (P70) subjected to CRS Hunter et al., 2009 ↓H3K9me ↓H3K9me3 Prefrontal cortex Young female rats subjected to early maternal separation (low fear-conditioned startle) Kao et al., 2012 ↑H3K9me3 ↓GR Amygdala; hippocampus Adult bHR (low anxiety) rats Chaudhury et al., 2014 ↓G9a ↓H3K9me2 Whole brain Adult mice treated with G9a inhibitors (low-anxiety phenotype) Wang et al., 2018 ↑G9a ↑H3K9me2 Nucleus accumbens Viral G9a overexpression in male adult rats (high anxiety phenotype) Anderson et al., 2018 ↓HDAC2 ↑HDAC3 ↓HDAC8 ↓Suv39 h1 Hippocampus Young adult rats (2 months) subjected to early maternal separation (anxiety phenotype) Suri et al., 2013 ↓H3K9ac ↓GR ↑CRF ↑SIRT6 Amygdala (central) Male adult mice were infused with CORT (chronic anxiety) Tran et al., 2015 ↓H3K9ac ↓H4K12ac Hippocampus Adult male rats subjected to CVS Ferland and Schrader, 2011 ↓HDAC5 Nucleus accumbens Mice subjected to CSDS (chronic anxiety) Renthal et al., 2007 ↑HDAC2 ↓H3K9ac Amygdala (central) Adult P rats bred for alcohol preference (anxiety phenotype) Moonat et al., 2013 P, postnatal day.
In this issue
The Epigenetics of Anxiety Pathophysiology: A DNA Methylation and Histone Modification Focused Review
