in this chapter introduction 165 current animal models of ... 2018 chapter.pdfcomorbidity, (3)...

In this Chapter

Introduction 165

Current Animal Models of Comorbid AUD and PTSD 167

A Genetic Mouse Model for Comorbid AUD and PTSD 168

Mechanisms for Comorbid AUD and PTSD 169

The Common Genetic Factors Hypothesis 170

The Self-Medication Hypothesis 172

The HPA Axis Dysregulation Hypothesis 174

Highlights 175

References 176

A Genetic Mouse Model forComorbid Alcohol Use

Disorder andPosttraumatic Stress

DisorderJulia A. Chester

Purdue University, West Lafayette, IN, United States

IntroductionThe role of stress in the development of drug use disorders has been the subject

of intensive study for many decades. Much progress has been made in under-

standing the biological and behavioral mechanisms that contribute to individual

vulnerability and resilience toward drug-seeking behavior. Stress potently regu-

lates cognitive and emotional brain mechanisms, including those that relate to

anxiety, and influences initial propensity to use drugs as well as maintenance of

drug-seeking behaviors.

Of all the substance use disorders, alcohol use disorder (AUD) is the most com-

mon. Data from the 2012 to 2013 National Epidemiologic Survey on Alcohol

and Related Conditions III (NESARC-III) using the new AUD classifications in the

Diagnostic and Statistical Manual for Mental Disorders (DSM-5) indicated the

12-month and lifetime prevalence of AUD was 13.9% and 29.1%, respectively

(Grant et al., 2015). In the United States alone, AUD has an estimated

economic impact of $249 billion dollars each year. Alcohol consumption is the

fifth leading cause of premature death, with 88,000 deaths each year and an

estimated 2.5 million years of lost life of those who died (Stahre, Roeber,

Kanny, Brewer, & Zhang, 2014).

AUD has the highest cooccurrence (termed comorbidity) with mental illnesses

in both adolescents and adults (Lipari et al., 2014). Identifying the behavioral

165Neurobiology of Abnormal Emotion and Motivated Behaviors.

DOI: https://doi.org/10.1016/B978-0-12-813693-5.00009-5

© 2018 Elsevier Inc. All rights reserved.

and neurobiological mechanisms that underlie psychiatric comorbidities with

AUD is a primary focus of the National Institute on Alcohol Abuse and

Alcoholism’s strategic research plan. Of particular interest is addressing the

increasingly high incidence of comorbid AUD and posttraumatic stress disorder

(PTSD).

PTSD can develop in people after exposure to various types of trauma,

such as violence, physical abuse, accidents, natural disasters, and war

(Vieweg et al., 2006). Nearly 8% of the US population will develop PTSD

at some point in their lifetime; in women, the statistic is approximately

10%�13%, nearly double that in men (Kessler, Sonnega, Bromet, Hughes,

& Nelson, 1995).

High comorbid rates of AUD and PTSD have been documented for decades

(Kessler et al., 1996) and are continuing to rise in military personnel and veterans

(Allen, Crawford, & Kudler, 2016). Approximately 30% of people in the general

population with PTSD also have a comorbid AUD and most studies report a

higher comorbidity prevalence in men than women (Kessler et al., 1995).

However, emerging evidence suggests that type of trauma and severity of PTSD

in combination with other risk factors for AUD may disproportionally impact

lifetime prevalence of comorbid AUD and PTSD in women (Pietrzak, Van Ness,

Fried, Galea, & Norris, 2012).

People with comorbid AUD and PTSD represent a special population that suffer

greater negative consequences than those with either disorder alone, such as

more severe anxiety symptoms, greater alcohol drinking relapse rates, incurrence

of higher medical costs, poorer treatment outcomes, and greater losses in work

productivity (Blanco et al., 2013). There is currently a critical need to identify

appropriate prevention and treatment strategies for comorbid AUD and PTSD.

Although there are several promising pharmacological compounds currently

being tested in clinical trials, there are no medications approved by the Food and

Drug Administration specifically indicated for the treatment of comorbid AUD

and PTSD.

Preclinical research in animal models is necessary to understand how genetic

and biological mechanisms contribute to the risk for developing comorbid

AUD and PTSD in humans and to identify specific and efficacious biological

and behavioral treatments for these comorbid disorders. The goals of this

chapter are to highlight: (1) epidemiological data on the prevalence of

comorbid AUD and PTSD in humans, (2) theories that attempt to explain

comorbidity, (3) current animal models of comorbid AUD and PTSD, and (4)

findings from our laboratory in a unique genetic mouse model of comorbid

AUD and PTSD. We will discuss the translational applicability of this model to

speed the identification of novel treatments for humans suffering with

comorbid AUD and PTSD.

Neurobiology of Abnormal Emotion and Motivated Behaviors

166

Current Animal Models of ComorbidAUD and PTSDMimicking the characteristics of stressors and how they impact an organism in

an ecologically relevant way is critical for developing valid animal models of

stress-related disease in humans. Stressor characteristics, including physical,

chemical, emotional and cognitive facets, interact with genetic, biological, and

environmental factors to produce complex responses that manifest as either

adaptive or maladaptive effects on the organism. A primary goal of translational

research and the development of valid animal models is to isolate the various

heterogeneous factors and explore interactive effects to help understand how

these factors promote vulnerability or resilience against stress-related disorders

and to develop treatments once the pathological condition has manifested.

Animal models for stress and alcohol interactions have been in existence for

almost 100 years, and these models are continually being refined to show robust

and reproducible effects that mimic specific aspects of complex human dis-

orders. Models for comorbid psychiatric disorders are just beginning to emerge

during a time of exponential growth in knowledge regarding how genetic and

environmental factors interact to contribute to brain function and behavior.

Stress effects on alcohol drinking behavior in rodents are not straightforward

and appear to depend on many factors such as preexposure to alcohol, timing

and duration of stress exposure in relation to drinking, chronicity and type of

stressor, and type of alcohol drinking procedure (Becker, Lopez, & Doremus-

Fitzwater, 2011; Noori, Helinski, & Spanagel, 2014). Results from several

laboratories, including our own, have shown that rodents with a genetic pre-

disposition toward high alcohol drinking are more sensitive to stress-induced

drinking behavior than their low alcohol drinking counterparts. For example,

footshock exposure reinstated alcohol intake to a greater extent in the Alcohol-

Accepting (AA), High-Alcohol-Drinking (HAD), and alcohol-preferring (P) rats

(Vengeliene et al., 2003) and in Marchigian Sardinian alcohol-preferring (msP)

rats (Hansson et al., 2006) compared to Wistar rats. Restraint stress increased

alcohol intake in male P and HAD but not in low-(NP/LAD)-alcohol drinking rat

lines (Chester, Blose, Zweifel, & Froehlich, 2004). Repeated, intermittent

restraint stress exposure prior to limited-access alcohol sessions produced a sus-

tained increase in alcohol intake over time in male but not female high-alcohol-

preferring (HAP2) mice (Chester, de Paula Barrenha, DeMaria, & Finegan,

2006). Although these models indicate stress-induced drinking effects, they are

not necessarily models of PTSD and comorbid AUD, specifically.

Developing translational rodent models specifically for PTSD is an emerging

research area. PTSD diagnosis in humans requires that the individual was exposed

to a specific traumatic stressor. Thus many PTSD models involve exposing animals

to physical and psychological traumas and measuring resultant behavioral


167

responses that mimic clinical signs of PTSD symptomatology, such as fear and

anxiety (Flandreau & Toth, 2017). The highly conserved neuroendocrine circuitry

in mammals also allows for measurement of hypothalamic-pituitary-adrenal (HPA)

axis and other neuroendocrine factors in conjunction with anxiety-related beha-

viors. PTSD models have included exposure to physical stressors such as footshock,

pain, restraint, and cold temperatures; arguably these physical stressors also invoke

aspects of psychological trauma. Models of specific psychological trauma include

predator stress and social stressors such as housing instability or social defeat.

Furthermore, many of these models take advantage of individual differences in

responses that may reflect vulnerability or resilience toward developing PTSD, as

well as manipulate factors that may increase the likelihood or severity of the PTSD-

like behavior, such as repeated or prolonged exposure to the stressors and/or

exposure during early life development (Butler, Karkhanis, Jones, & Weiner, 2016).

There are also many learning models of PTSD that rely on fear-conditioning

procedures to mimic “maladaptive” learning processes thought to be a primary

factor in the development and maintenance of PTSD symptomatology (Lissek

& van Meurs, 2015). Associative fear learning involves the pairing of an initially

neutral conditioned stimulus (CS) with an aversive unconditioned stimulus (US;

usually a footshock or predator odor) and then measuring the behavioral

response to the CS. Several forms of “maladaptive” learning processes with rel-

evance to the clinical condition have been partially validated in animal models,

including impairments in the extinction process, incubation of fear, stimulus

generalization, and sensitization to stress.

Demonstrating model validity for comorbid AUD and PTSD has been difficult

due largely to an inability to produce escalated and sustained stress-induced

alcohol intake—characteristics of human behavior. Previous work has shown

increased alcohol intake following traumatic stress using a predator odor model

in rats (Edwards et al., 2013; Manjoch et al., 2016), with the “stress-reactive”

rats showing persistent increased alcohol intake. In another study, investigators

used a stress-enhanced fear learning model to show that repeated exposure to

footshock prior to alcohol access enhanced the acquisition of alcohol intake in

rats, but stress had no effects on drinking in rats that had already established

drinking behavior (Meyer, Long, Fanselow, & Spigelman, 2013). Much work is

needed to identify new models and increase the construct and predictive

validity of existing animal models of comorbid AUD and PTSD. The field

requires many different models to address the heterogeneity of the comorbid

disorders and demonstrate construct and predictive validity to appropriately

identify individualized treatment strategies in humans.

A Genetic Mouse Model for Comorbid AUD and PTSDSome of the most exciting tools for studying genetic factors that contribute to

the development of AUD are rodent lines that have been selectively bred for


168

differences in propensity to consume alcohol (Li & McBride, 1995). These lines

are extremely valuable for identifying traits that are correlated with the

selection phenotypes of high or low alcohol drinking and elucidating the ways

in which environmental factors, such as exposure to stress, may interact with a

genetic predisposition toward alcohol drinking behavior to influence the

development of AUD and comorbid disorders.

In our work, we use replicate mouse lines selectively bred for high (HAP1/

HAP2/HAP3) or low alcohol preference (LAP1/LAP2/LAP3). These mouse lines

were separately selected from a progenitor population of outbred HS/Ibg

mice (Grahame, Li, & Lumeng, 1999), an intercross of eight different inbred

mouse strains (A, AKR, BALB/c, C3H/2, C57BL, DBA/2, Is/Bi, and RIII), which

contributes a relatively diverse set of possible alleles to “capture” during the

selective breeding process. Thus this is a model for genetic heterogeneity in

humans and is extremely relevant for translational approaches to identify

genetic contributions to behavior.

The use of more than one pair of selectively bred lines to identify genetic corre-

lations between traits is a very strong experimental design because genetic drift

can occur between a single pair of selected lines over generations of selective

breeding. Replicate lines do not exist for many of the selectively bred rat lines

used in the studies reviewed herein, reinforcing the importance of using

multiple animal models to obtain converging evidence for genetic relationships

between traits. The identification of a correlated trait in more than one pair of

replicate lines robustly increases the probability that the relationship between

the correlated trait and the selection phenotype reflects a true genetic correla-

tion (Crabbe, Phillips, Kosobud, & Belknap, 1990). To date, several traits

have been identified in the HAP/LAP lines that are associated with high alcohol

preference or low alcohol preference, such as differences in sensitization to the

locomotor-stimulant effects of alcohol (Grahame, Rodd-Henricks, Li, &

Lumeng, 2000), conditioned place preference (Grahame, Chester, Rodd-

Henricks, Li, & Lumeng, 2001) and conditioned taste aversion to alcohol

(Chester, Lumeng, Li, & Grahame, 2003), emotional reactivity (Matson &

Grahame, 2015), affect-related behaviors (Can, Grahame, & Gould, 2012), and

impulsivity (Oberlin & Grahame, 2009). We have compelling data indicating

that mouse lines selectively bred for high or low alcohol preference are a good

model for genetic vulnerability factors that may contribute to the development

of comorbid AUD and PTSD in humans (discussed below).

Mechanisms for Comorbid AUD andPTSDGenetic factors in combination with environmental and biological factors

certainly influence the risk for developing comorbid AUD and PTSD, through


169

interactive and permissive mechanisms, and the roles of these risk factors are

the subject of intense investigation in the field of psychiatric behavioral

genetics. Investigators have focused on several primary hypotheses to explain

the cooccurrence of AUD and PTSD. From a clinical treatment perspective, it is

important to differentiate the role of various factors and identify time of symp-

tom onset in the context of the individual’s personal history, such as trauma

and alcohol exposure, to improve diagnostic accuracy and treatment outcomes

(Shivani, Goldsmith, & Anthenelli, 2002).

The Common Genetic Factors HypothesisRecent evidence indicates common genetic factors play an important role in the risk

for developing comorbid AUD and PTSD, specifically. Genetic correlation studies in

humans report significant overlap in genetic factors contributing to both disorders

(Sartor et al., 2011). However, the ultimate challenge in identifying risk factors for

comorbid disease is unraveling the complex gene-environment interactions.

Testing the Common Genetic Factors Hypothesis WithAcoustic Startle Phenotypes

General Acoustic Startle Response

The acoustic startle reflex is an adaptive, defensive behavior shown by all

mammalian species in response to intense acoustic stimuli. Acoustic startle

phenotypes have served as useful measures of cognition- and emotion-related

brain mechanisms that may be associated with genetic risk for AUD and anxiety

disorders in humans (Grillon, Dierker, & Merikangas, 1997).

A genetic relationship between selection for high alcohol preference and

greater acoustic startle reactivity has been repeatedly shown in rat lines selec-

tively bred for differences in alcohol consumption (Acewicz et al., 2012;

Chester, Blose, & Froehlich, 2003, 2004; Jones et al., 2000). In the HAP and

LAP selected mouse lines, we have consistently found higher baseline startle

responses in HAP mice than LAP mice from both replicates 1 and 2 (Barrenha &

Chester, 2007, 2012; Barrenha, Coon, & Chester, 2011; Breit & Chester, 2016;

Chester & Barrenha, 2007; Chester, Kirchhoff, & Barrenha, 2014; Chester &

Weera, 2017; Powers & Chester, 2014). These data in selected rodent lines pro-

vides strong evidence that genes that regulate acoustic startle reactivity also

influence propensity to drink alcohol.

Conditioned Fear-Potentiated StartleOne of the clinical features of PTSD is an exaggerated startle reflex and has

been suggested to indicate an overblown response to danger-related cues in

the environment that may signal the threat of aversive stimuli (Grillon, 2002).

Fear-potentiated startle (FPS) is a model of fear learning that is commonly used

to assess anticipatory fear/anxiety in both humans (Grillon, Ameli, Merikangas,

Woods, & Davis, 1993) and rodents (Davis, Falls, Campeau, & Kim, 1993).


170

In rodents, FPS is produced through classical conditioning procedures that

involve repeated pairings of aversive stimuli (usually electric shock) with a

neutral stimulus (such as a light) to form an association between the two stimuli.

Acoustic startle stimuli are then presented in the presence and absence of the

cues that predict aversive stimuli. FPS is evidenced by a potentiated startle

response, indicating anticipatory fear or anxiety, in the presence of the cues

associated with, or predictive of, aversive stimuli. Several key brain areas modu-

late the acquisition and expression of FPS, including the lateral, basolateral, and

central nucleus of the amygdala. The central nucleus of the amygdala projects to

brainstem nuclei critical for the expression of FPS. In addition, cortical areas,

such as the perirhinal cortices, project to the lateral and basolateral nuclei of the

amygdala and modulate multimodal processing of conditioned stimuli (auditory

or visual) and expression of FPS (Davis et al., 1993).

FPS has been suggested to be a particularly relevant translational model for

PTSD and an index of associative learning processes that support the develop-

ment and maintenance of PTSD symptomatology (Grillon, Southwick, &

Charney, 1996). Evidence in humans indicates that FPS represents a phenotype

predictive of genetic risk for developing anxiety-related disorders (Grillon,

Dierker, & Merikangas, 1998).

In rats that differ in genetic propensity toward alcohol drinking, McKinzie et al.

(2000) found that P rats selectively bred for high alcohol preference show greater

FPS than NP rats selectively bred for low alcohol preference. We have demon-

strated strong evidence for a genetic correlation between FPS and alcohol prefer-

ence in the selectively bred HAP/LAP lines. HAP lines of both replicate lines 1 and

2 show greater FPS than LAP lines (Barrenha & Chester, 2007, 2012; Barrenha

et al., 2011; Breit & Chester, 2016; Chester et al., 2014; Chester & Weera,

2017). Male HAP2 mice often show greater FPS than female HAP2 mice

(Barrenha et al., 2011; Chester et al., 2014), a finding consistent with data from

animal models of PTSD, suggesting that male animals are more susceptible to

stress-related anxiety (Cohen & Yehuda, 2011).

This genetic association between greater FPS and high alcohol preference in

replicate selected mouse lines that are alcohol-naı̈ve may suggest that the high

rate of comorbidity between PTSD and AUD in humans is due, in part, to the

influence of common genetic risk factors for both psychiatric disorders. These

findings in a genetic mouse model support reports of increased prevalence of

comorbid AUD and anxiety disorders in relatives of people with AUD and/or

anxiety disorders (Merikangas et al., 1998).

Prepulse Inhibition of the Acoustic Startle ResponseOne common procedure for assessing cognition-related processing in mam-

mals is prepulse inhibition (PPI). PPI reflects adaptive sensory-motor gating

processes that regulate incoming information to the brain (Swerdlow, Braff, &

Geyer, 2016) and is a well-established procedure for cross-species modeling of


171

brain-behavior functions. Deficits in PPI (defined as a reduction of a startle

response to an acoustic stimulus when that stimulus is preceded by a weak

prepulse stimulus) have been noted in people with psychiatric disorders such

as schizophrenia, obsessive compulsive disorder, and PTSD (Braff, Geyer, &

Swerdlow, 2001). Deficits in PPI have also been reported in individuals that are

genetically related to subjects clinically diagnosed with AUD but do not them-

selves have the disorder, suggesting that disrupted PPI might be a phenotypic

marker for AUD vulnerability.

Alcohol-naı̈ve rats selectively bred to prefer or avoid alcohol showed com-

parable levels of PPI (Acewicz et al., 2012 [Warsaw alcohol high-preferring/low-

preferring lines]; Jones et al., 2000 [P/NP lines]). We found that baseline PPI

was higher in the selectively bred HAP1/2 lines than LAP1/2 lines (Chester &

Barrenha, 2007), suggesting there are common genetic mechanisms that regu-

late PPI and alcohol preference in these mouse lines, but the direction of the

effect was reversed from that reported in genetically at-risk humans. We subse-

quently replicated the greater baseline PPI in HAP2 versus LAP2 mice and

showed that alcohol administration increased PPI in HAP2 but not in LAP2 mice

(Powers & Chester, 2014). Interestingly, this finding was similar to effects of

low-dose alcohol reported in human subjects with higher baseline PPI levels

(Hutchison et al., 1997). Hutchison et al. speculated that their results could

reflect sensitivity differences in alcohol-induced changes in dopaminergic brain

function. This hypothesis fits with the larger literature indicating a prominent

role for dopamine and its receptors in modulating PPI (Swerdlow et al., 2016)

and alcohol-related behaviors (Koob & Volkow, 2016). Furthermore, many

studies show differences in dopaminergic system function between rats selec-

tively bred for high or low alcohol intake (Murphy et al., 2002). In the HAP1/

LAP1 selected lines, a single nucleotide polymorphism sequence difference was

found near the dopamine D2 receptor (Bice, Lai, Zhang, & Foroud, 2011) and

D2 mRNA expression differences have been found in the hippocampus and

nucleus accumbens (Bice, Liang, Zhang, Strother, & Carr, 2008).

The Self-Medication HypothesisThe self-medication hypothesis states that AUD arises because individuals

attempt to mitigate symptoms of psychological distress symptoms by consum-

ing alcohol (Cappell & Herman, 1972). In theory, alcohol consumption is then

negatively reinforced if alcohol successfully reduces adverse symptoms like

anxiety which leads to greater alcohol intake over time. Evidence in the PTSD

literature largely supports this process and suggests that the severity of PTSD

symptoms predict alcohol craving and intake in a prospective and proximal

manner (Langdon et al., 2016).

With respect to genetic contributions to the self-medication hypothesis,

several studies suggest that humans with genetic predisposition toward AUD


172

and/or anxiety disorders are more sensitive to the anxiolytic effects of alcohol

(Sher & Levenson, 1982; Sinha, Robinson, & O’Malley, 1998). However,

Zimmermann, Spring, Wittchen, and Holsboer (2004) did not find a difference

in the effect of alcohol on anxiety between men with and without a family

history of AUD using a fear potentiation procedure.

There have been a few reports of alcohol effects on measures of anxiety in rats

that differ in genetic propensity toward alcohol consumption. Colombo et al.

(1995) reported that the selectively bred Sardinian alcohol-preferring (sP) rats

showed greater innate anxiety in the elevated plus maze than the alcohol-

nonpreferring line (sNP) and that voluntary alcohol consumption in sP rats

reduced anxiety. Stewart, Gatto, Lumeng, Li, and Murphy (1993) found greater

anxiety in P rats than in NP rats (Indiana lines) in three tests of anxiety, and

that alcohol produced anxiolytic effects in P but not NP rats. These findings

suggest that the self-medication hypothesis may be particularly relevant for

exploring mechanisms related to AUD risk in organisms that have increased

genetic propensity for high alcohol consumption and anxiety-related behavior.

The HAP/LAP mouse lines have been useful for testing the self-medication

hypothesis in a unique mouse model for genetic predisposition toward develop-

ing comorbid AUD and PTSD in humans. Using the FPS procedure, we reported

that male and female HAP mice from both replicates show an anxiolytic response

to alcohol, but the LAP lines did not (Barrenha et al., 2011). This finding provides

strong evidence indicating genes that regulate anxiolytic response to alcohol

also regulate propensity toward high alcohol preference, and thus this may be

one of the mechanisms contributing to AUD and PTSD comorbidity in humans.

Results of several studies suggest that mice will drink alcohol in response to

stress-induced anxiety. Footshock stress exposure during adolescence increased

acoustic startle reactivity and alcohol drinking behavior in both male and female

HAP1 mice (Chester, Barrenha, Hughes, & Keuneke, 2008). Breit and Chester

(2016) reported that repeated footshock stress during adolescence increased

the magnitude of FPS in adult HAP2 but not LAP2 mice, indicating genetic pro-

pensity toward high alcohol intake may be linked to vulnerability toward-stress-

induced anxiety in adulthood. Interestingly, adolescent footshock stress did not

alter alcohol-induced conditioned place preference in adult HAP2 or LAP2 mice,

suggesting that the adolescent footshock-induced increase in alcohol drinking

reported in Chester et al. (2008) was due to changes in anxiety-related

mechanisms rather than to direct stress-induced changes in alcohol reward sen-

sitivity. Further, we recently demonstrated construct validity in the HAP/LAP

mice as a model for comorbid PTSD and AUD. Repeated exposure to fear-

conditioning enhanced limited-access alcohol drinking in HAP2 but not LAP2

mice (Chester & Weera, 2017). Overall, these findings indicate that genetic vul-

nerability toward high alcohol consumption is associated with greater sensitivity

to anxiety-related behavior and stress-induced alcohol drinking behavior.


173

The HPA Axis Dysregulation HypothesisA significant area of focus in the literature concerns exploring the neuroendo-

crine system as a mechanistic link for comorbid AUD and PTSD. It is beyond

the scope of this chapter to discuss the plethora of research findings in sup-

port of this mechanistic hypothesis (Anthenelli, 2010). Here, we highlight a

few relevant findings as they relate to documented HPA axis correlates in

humans with AUD or PTSD and in outbred and genetically selected rodent

models.

In humans, cortisol is the primary adrenal glucocorticoid and in rodents it is

corticosterone. Glucocorticoids exert negative feedback inhibition on the hypo-

thalamus and pituitary gland to suppress further activation of the HPA axis.

Negative feedback inhibition is regulated by neural signals from various brain

regions such as the amygdala and hippocampus once the stressor is removed

(McEwen, Brinton, Harrelson, & Rostene, 1987). Variations in HPA axis function

have been suggested to represent a biological marker for PTSD (de Kloet et al.,

2005; Yehuda et al., 2000) and AUD (Stephens & Wand, 2012). A prospective

longitudinal study found that people who developed PTSD after motor vehicle

accident trauma had lower cortisol levels after the trauma compared to people

who did not subsequently develop PTSD (McFarlane, Atchison, & Yehuda,

1997). In people with comorbid PTSD and AUD, Brady et al. (2006) reported

blunted HPA axis function that was similar to responses seen in people with a

single diagnosis of either AUD or PTSD.

An important, unresolved question is whether HPA axis dysregulation is pres-

ent before the onset of PTSD or occurs as a consequence of PTSD. There is

some evidence that healthy individuals who are at greater genetic risk

for developing PTSD (family history positive) have low baseline cortisol levels

(e.g., Yehuda et al., 2000). Also, studies in humans with increased genetic

risk for AUD have reported blunted HPA axis responsiveness to stressors (e.g.,

Adinoff, Junghanns, Kiefer, & Krishnan-Sarin, 2005; Wand, Mangold, Ali, &

Giggey, 1999).

A lower corticosterone response to anxiogenic stressors in outbred rats

has been shown to predict greater susceptibility to develop PTSD-like beha-

viors (Cohen et al., 2006; King, Abend, & Edwards, 2001; Whitaker,

Farooq, Edwards, & Gilpin, 2016; Zoladz, Fleshner, & Diamond, 2012). In

the selectively bred P/NP rat lines, P rats showed a smaller corticosterone

output profile in response to stress compared to NP rats (Prasad &

Prasad, 1995).

Our work in HAP/LAP mice aligns with these findings in rats and humans and

suggests that a low level of corticosterone in response to trauma is a biological

marker for PTSD-like behavior and is correlated with genetic propensity toward

high alcohol preference. We showed that HAP2 mice, when compared to LAP2


174

mice, have lower levels of corticosterone 2 hours after fear-conditioning

(Chester et al., 2014). In this same study we also reported a similar line differ-

ence (LAP2.HAP2), but in males only, when blood was sampled at the end

of the 1-hour FPS test. The corresponding FPS data also indicated the line dif-

ference (HAP2. LAP2) was greater in male than female mice. These data are

consistent with findings in other animal models of PTSD indicating that male

animals are more susceptible to stress-related anxiety (Cohen & Yehuda,

2011). One possible interpretation of these findings, and a hypothesis we are

currently exploring, is that lower corticosterone levels in HAP2 mice may

reflect greater negative feedback inhibition on the HPA axis due to enhanced

glucocorticoid receptor signaling in the brain and pituitary, rather than

reduced corticosterone output from the adrenal glands (Yehuda, 2001). We

reported additional support for this hypothesis in Powers and Chester (2014)

where a line difference in basal circulating corticosterone (LAP2.HAP2) was

seen after repeated stress exposure. Additional work that assesses a variety of

stress-induced biological and behavioral endpoints in these mouse lines will

help fill important gaps in the literature.

The idea that low cortisol after trauma is a causal risk factor for PTSD is sup-

ported by reported effects where exogenous treatment with cortisol during a

trauma reduced the subsequent development (Schelling et al., 2001), and

symptoms of, PTSD (Aerni et al., 2004). Rat models of PTSD have shown similar

results in which exogenous administration of corticosterone reduced the PTSD-

like behaviors (Cohen et al., 2006; Whitaker et al., 2016). However, we did not

see any effect of exogenous corticosterone administration on FPS in HAP2 or

LAP2 mice when given during fear-conditioning (Chester et al., 2014). These

data support the idea that cortisol or related compounds might be a promising

preventative treatment for individuals at risk for PTSD, but much more work is

needed in this arena.

Highlights� There is a critical need to identify new models and increase the construct

and predictive validity of existing animal models of comorbid AUD and

PTSD.

� Acoustic startle and HPA axis phenotypes are useful translational measures

to explore genetic and biological risk factors that may predict risk for

developing comorbid AUD and PTSD.

� Genetic vulnerability toward high alcohol consumption is associated with

greater sensitivity to anxiety-related behavior, stress-induced alcohol drink-

ing behavior, and HPA axis dysfunction.

� Mouse lines selectively bred for high or low alcohol preference (HAP/LAP

lines) are a relevant animal model for genetic vulnerability factors that may

contribute to the development of comorbid AUD and PTSD in humans.


175

ReferencesAcewicz, A., Mierzejewski, P., Jastrzebska, A., Kolaczkowski, M., Wesolowska, A., Korkosz, I., . . .

Bienkowski, P. (2012). Acoustic startle responses and prepulse inhibition of acoustic startle

responses in Warsaw alcohol high-preferring (WHP) and Warsaw alcohol low-preferring

(WLP) rats. Alcohol and Alcoholism (Oxford, Oxfordshire), 47(4), 386�389.

Adinoff, B., Junghanns, K., Kiefer, F., & Krishnan-Sarin, S. (2005). Suppression of the HPA axisstress-response: Implications for relapse. Alcoholism, Clinical and Experimental Research, 29

(7), 1351�1355.

Aerni, A., Traber, R., Hock, C., Roozendaal, B., Schelling, G., Papassotiropoulos, A., . . . deQuervain, D. J. (2004). Low-dose cortisol for symptoms of posttraumatic stress disorder.

The American Journal of Psychiatry, 161(8), 1488�1490.

Allen, J. P., Crawford, E. F., & Kudler, H. (2016). Nature and treatment of comorbid alcohol

problems and post traumatic stress disorder among American military personnel andveterans. Alcohol Research, 38(1), 133�140.

Anthenelli, R. M. (2010). Focus on: Comorbid mental health disorders. Alcohol Research & Health:

The Journal of the National Institute on Alcohol Abuse and Alcoholism, 33(1�2), 109�117.

Barrenha, G. D., & Chester, J. A. (2007). Genetic correlation between innate alcohol prefer-ence and fear-potentiated startle in selected mouse lines. Alcoholism, Clinical and

Experimental Research, 31(7), 1081�1088.

Barrenha, G. D., & Chester, J. A. (2012). Effects of cross-fostering on alcohol preference andcorrelated responses to selection in high- and low-alcohol-preferring mice. Alcoholism,

Clinical and Experimental Research, 36(12), 2065�2073.

Barrenha, G. D., Coon, L. E., & Chester, J. A. (2011). Effects of alcohol on the acquisition and

expression of fear-potentiated startle in mouse lines selectively bred for high and lowalcohol preference. Psychopharmacology (Berl), 218(1), 191�201.

Becker, H. C., Lopez, M. F., & Doremus-Fitzwater, T. L. (2011). Effects of stress on alcohol

drinking: A review of animal studies. Psychopharmacology (Berl), 218(1), 131�156.

Bice, P. J., Lai, D., Zhang, L., & Foroud, T. (2011). Fine mapping quantitative trait loci thatinfluence alcohol preference behavior in the high and low alcohol preferring (HAP and

LAP) mice. Behavior Genetics, 41(4), 565�570.

Bice, P. J., Liang, T., Zhang, L., Strother, W. N., & Carr, L. G. (2008). Drd2 expression in the

high alcohol-preferring and low alcohol-preferring mice. Mammalian Genome: OfficialJournal of the International Mammalian Genome Society, 19(2), 69�76.

Blanco, C., Xu, Y., Brady, K., Perez-Fuentes, G., Okuda, M., & Wang, S. (2013). Comorbidity

of posttraumatic stress disorder with alcohol dependence among US adults: Results fromNational Epidemiological Survey on Alcohol and Related Conditions. Drug and Alcohol

Dependence, 132(3), 630�638.

Brady, K. T., Waldrop, A. E., McRae, A. L., Back, S. E., Saladin, M. E., Upadhyaya, H. P., . . .Randall, P. K. (2006). The impact of alcohol dependence and posttraumatic stress disorderon cold pressor task response. Journal of Studies on Alcohol, 67(5), 700�706.

Braff, D. L., Geyer, M. A., & Swerdlow, N. R. (2001). Human studies of prepulse inhibition of

startle: Normal subjects, patient groups, and pharmacological studies. Psychopharmacology

(Berl), 156(2�3), 234�258.Breit, K. R., & Chester, J. A. (2016). Effects of chronic stress on alcohol reward- and anxiety-

related behavior in high- and low-alcohol preferring mice. Alcoholism, Clinical and

Experimental Research, 40(3), 482�490.Butler, T. R., Karkhanis, A. N., Jones, S. R., & Weiner, J. L. (2016). Adolescent social isolation as

a model of heightened vulnerability to comorbid alcoholism and anxiety disorders.

Alcoholism, Clinical and Experimental Research, 40(6), 1202�1214.

Can, A., Grahame, N. J., & Gould, T. D. (2012). Affect-related behaviors in mice selectivelybred for high and low voluntary alcohol consumption. Behavior Genetics, 42(2), 313�322.


176

Cappell, H., & Herman, C. P. (1972). Alcohol and tension reduction. A review. Quarterly

Journal of Studies on Alcohol, 33(1), 33�64.

Chester, J. A., & Barrenha, G. D. (2007). Acoustic startle at baseline and during acute alcoholwithdrawal in replicate mouse lines selectively bred for high or low alcohol preference.

Alcoholism, Clinical and Experimental Research, 31(10), 1633�1644.

Chester, J. A., Barrenha, G. D., Hughes, M. L., & Keuneke, K. J. (2008). Age- and sex-

dependent effects of footshock stress on subsequent alcohol drinking and acoustic startlebehavior in mice selectively bred for high-alcohol preference. Alcoholism, Clinical and

Experimental Research, 32(10), 1782�1794.

Chester, J. A., Blose, A. M., & Froehlich, J. C. (2003). Further evidence of an inverse geneticrelationship between innate differences in alcohol preference and alcohol withdrawal mag-

nitude in multiple selectively bred rat lines. Alcoholism, Clinical and Experimental Research,

27(3), 377�387.

Chester, J. A., Blose, A. M., & Froehlich, J. C. (2004). Acoustic startle reactivity during acutealcohol withdrawal in rats that differ in genetic predisposition toward alcohol drinking:

Effect of stimulus characteristics. Alcoholism, Clinical and Experimental Research, 28(5),

677�687.

Chester, J. A., Blose, A. M., Zweifel, M., & Froehlich, J. C. (2004). Effects of stress on alcoholconsumption in rats selectively bred for high or low alcohol drinking. Alcoholism, Clinical

and Experimental Research, 28(3), 385�393.

Chester, J. A., de Paula Barrenha, G., DeMaria, A., & Finegan, A. (2006). Different effects ofstress on alcohol drinking behaviour in male and female mice selectively bred for high

alcohol preference. Alcohol and Alcoholism (Oxford, Oxfordshire), 41(1), 44�53.

Chester, J. A., Kirchhoff, A. M., & Barrenha, G. D. (2014). Relation between corticosterone and

fear-related behavior in mice selectively bred for high or low alcohol preference. AddictionBiology, 19(4), 663�675.

Chester, J. A., Lumeng, L., Li, T. K., & Grahame, N. J. (2003). High- and low-alcohol-preferring

mice show differences in conditioned taste aversion to alcohol. Alcoholism, Clinical and

Experimental Research, 27(1), 12�18.Chester, J. A., & Weera, M. M. (2017). Genetic correlation between alcohol preference and

conditioned fear: Exploring a functional relationship. Alcohol (Fayetteville, N.Y.), 58,

127�137.

Cohen, H., & Yehuda, R. (2011). Gender differences in animal models of posttraumatic stressdisorder. Disease Markers, 30(2�3), 141�150.

Cohen, H., Zohar, J., Gidron, Y., Matar, M. A., Belkind, D., Loewenthal, U., . . . Kaplan, Z.

(2006). Blunted HPA axis response to stress influences susceptibility to posttraumatic stressresponse in rats. Biological Psychiatry, 59(12), 1208�1218.

Colombo, G., Agabio, R., Lobina, C., Reali, R., Zocchi, A., Fadda, F., & Gessa, G. L. (1995).

Sardinian alcohol-preferring rats: A genetic animal model of anxiety. Physiology & Behavior,

57(6), 1181�1185.Crabbe, J. C., Phillips, T. J., Kosobud, A., & Belknap, J. K. (1990). Estimation of genetic correla-

tion: Interpretation of experiments using selectively bred and inbred animals. Alcoholism,

Clinical and Experimental Research, 14(2), 141�151.

Davis, M., Falls, W. A., Campeau, S., & Kim, M. (1993). Fear-potentiated startle: A neural andpharmacological analysis. Behavioural Brain Research, 58(1�2), 175�198.

de Kloet, C. S., Vermetten, E., Geuze, E., Kavelaars, A., Heijnen, C. J., & Westenberg, H. G.

(2005). Assessment of HPA-axis function in posttraumatic stress disorder: Pharmacologicaland non-pharmacological challenge tests, a review. Journal of Psychiatric Research, 40(6),

550�567.

Edwards, S., Baynes, B. B., Carmichael, C. Y., Zamora-Martinez, E. R., Barrus, M., Koob, G. F.,

& Gilpin, N. W. (2013). Traumatic stress reactivity promotes excessive alcohol drinking andalters the balance of prefrontal cortex-amygdala activity. Translational Psychiatry, 3, e296.


177

Flandreau, E. I., & Toth, M. (2017). Animal models of PTSD: A critical review. Current Topics in

Behavioral Neurosciences, 10.1007/7854_2016_65.

Grahame, N. J., Chester, J. A., Rodd-Henricks, K., Li, T. K., & Lumeng, L. (2001). Alcohol placepreference conditioning in high- and low-alcohol preferring selected lines of mice.

Pharmacology, Biochemistry, and Behavior, 68(4), 805�814.

Grahame, N. J., Li, T. K., & Lumeng, L. (1999). Selective breeding for high and low alcohol

preference in mice. Behavior Genetics, 29(1), 47�57.Grahame, N. J., Rodd-Henricks, K., Li, T. K., & Lumeng, L. (2000). Ethanol locomotor sensitiza-

tion, but not tolerance correlates with selection for alcohol preference in high- and low-

alcohol preferring mice. Psychopharmacology (Berl), 151(2�3), 252�260.Grant, B. F., Goldstein, R. B., Saha, T. D., Chou, S. P., Jung, J., Zhang, H., . . . Hasin, D. S.

(2015). Epidemiology of DSM-5 alcohol use disorder: Results from the National

Epidemiologic Survey on Alcohol and Related Conditions III. JAMA Psychiatry, 72(8),

757�766.Grillon, C. (2002). Startle reactivity and anxiety disorders: Aversive conditioning, context, and

neurobiology. Biological Psychiatry, 52(10), 958�975.

Grillon, C., Ameli, R., Merikangas, K., Woods, S. W., & Davis, M. (1993). Measuring the time

course of anticipatory anxiety using the fear-potentiated startle reflex. Psychophysiology, 30(4), 340�346.

Grillon, C., Dierker, L., & Merikangas, K. R. (1997). Startle modulation in children at risk for

anxiety disorders and/or alcoholism. Journal of the American Academy of Child andAdolescent Psychiatry, 36(7), 925�932.

Grillon, C., Dierker, L., & Merikangas, K. R. (1998). Fear-potentiated startle in adolescent

offspring of parents with anxiety disorders. Biological Psychiatry, 44(10), 990�997.

Grillon, C., Southwick, S. M., & Charney, D. S. (1996). The psychobiological basis of post-traumatic stress disorder. Molecular Psychiatry, 1(4), 278�297.

Hansson, A. C., Cippitelli, A., Sommer, W. H., Fedeli, A., Bjork, K., Soverchia, L., . . .Ciccocioppo, R. (2006). Variation at the rat Crhr1 locus and sensitivity to relapse into

alcohol seeking induced by environmental stress. Proceedings of the National Academy ofSciences, 103(41), 15236�15241.

Hutchison, K. E., Rohsenow, D., Monti, P., Palfai, T., & Swift, R. (1997). Prepulse inhibition of

the startle reflex: preliminary study of the effects of a low dose of alcohol in humans.

Alcoholism: Clinical and Experimental Research, 21, 1312�1319.Jones, A. E., McBride, W. J., Murphy, J. M., Lumeng, L., Li, T. K., Shekhar, A., & McKinzie, D. L.

(2000). Effects of ethanol on startle responding in alcohol-preferring and -non-preferring

rats. Pharmacology, Biochemistry, and Behavior, 67(2), 313�318.Kessler, R. C., Nelson, C. B., McGonagle, K. A., Edlund, M. J., Frank, R. G., & Leaf, P. J. (1996).

The epidemiology of co-occurring addictive and mental disorders: Implications for preven-

tion and service utilization. The American Journal of Orthopsychiatry, 66(1), 17�31.

Kessler, R. C., Sonnega, A., Bromet, E., Hughes, M., & Nelson, C. B. (1995). Posttraumaticstress disorder in the National Comorbidity Survey. Archives of General Psychiatry, 52(12),

1048�1060.

King, J. A., Abend, S., & Edwards, E. (2001). Genetic predisposition and the development of

posttraumatic stress disorder in an animal model. Biological Psychiatry, 50(4), 231�237.Koob, G. F., & Volkow, N. D. (2016). Neurobiology of addiction: A neurocircuitry analysis.

Lancet Psychiatry, 3(8), 760�773.

Langdon, K. J., Fox, A. B., King, L. A., King, D. W., Eisen, S., & Vogt, D. (2016). Examinationof the dynamic interplay between posttraumatic stress symptoms and alcohol misuse

among combat-exposed Operation Enduring Freedom (OEF)/Operation Iraqi Freedom

(OIF) Veterans. Journal of Affective Disorders, 196, 234�242.

Li, T. K., & McBride, W. J. (1995). Pharmacogenetic models of alcoholism. Clinical Neuroscience(New York, N.Y.), 3(3), 182�188.


178

Lipari, R.N., Hedden, S.L., & Hughes, A. (2014). Substance use and mental health estimates

from the 2013 National Survey on Drug Use and Health: Overview of Findings. The CBHSQ

Report: September 4. Center for Behavioral Health Statistics and Quality, Substance Abuseand Mental Health Services Administration, Rockville, MD.

Lissek, S., & van Meurs, B. (2015). Learning models of PTSD: Theoretical accounts and psycho-

biological evidence. International Journal of Psychophysiology: Official Journal of the

International Organization of Psychophysiology, 98(3 Pt 2), 594�605.Manjoch, H., Vainer, E., Matar, M., Ifergane, G., Zohar, J., Kaplan, Z., & Cohen, H. (2016).

Predator-scent stress, ethanol consumption and the opioid system in an animal model of

PTSD. Behavioural Brain Research, 306, 91�105.Matson, L. M., & Grahame, N. J. (2015). Emotional reactivity to incentive downshift as a corre-

lated response to selection of high and low alcohol preferring mice and an influencing fac-

tor on ethanol intake. Alcohol (Fayetteville, N.Y.), 49(7), 657�664.

McEwen, B., Brinton, R., Harrelson, A., & Rostene, W. (1987). Modulatory interactionsbetween steroid hormones, neurotransmitters and neuropeptides in hippocampus.

Advances in Biochemical Psychopharmacology, 43, 87�102.

McFarlane, A. C., Atchison, M., & Yehuda, R. (1997). The acute stress response following

motor vehicle accidents and its relation to PTSD. Annals of the New York Academy ofSciences, 821, 437�441.

McKinzie, D. L., Sajdyk, T. J., McBride, W. J., Murphy, J. M., Lumeng, L., Li, T. K., &

Shekhar, A. (2000). Acoustic startle and fear-potentiated startle in alcohol-preferring (P)and -nonpreferring (NP) lines of rats. Pharmacology, Biochemistry, and Behavior, 65(4),

691�696.

Merikangas, K. R., Stevens, D. E., Fenton, B., Stolar, M., O’Malley, S., Woods, S. W., & Risch,

N. (1998). Co-morbidity and familial aggregation of alcoholism and anxiety disorders.Psychological Medicine, 28(4), 773�788.

Meyer, E. M., Long, V., Fanselow, M. S., & Spigelman, I. (2013). Stress increases voluntary

alcohol intake, but does not alter established drinking habits in a rat model of posttrau-

matic stress disorder. Alcoholism, Clinical and Experimental Research, 37(4), 566�574.Murphy, J. M., Stewart, R. B., Bell, R. L., Badia-Elder, N. E., Carr, L. G., McBride, W. J., . . . Li,

T. K. (2002). Phenotypic and genotypic characterization of the Indiana University rat lines

selectively bred for high and low alcohol preference. Behavior Genetics, 32(5), 363�388.

Noori, H. R., Helinski, S., & Spanagel, R. (2014). Cluster and meta-analyses on factors influenc-ing stress-induced alcohol drinking and relapse in rodents. Addiction Biology, 19(2),

225�232.

Oberlin, B. G., & Grahame, N. J. (2009). High-alcohol preferring mice are more impulsive thanlow-alcohol preferring mice as measured in the delay discounting task. Alcoholism, Clinical

and Experimental Research, 33(7), 1294�1303.

Pietrzak, R. H., Van Ness, P. H., Fried, T. R., Galea, S., & Norris, F. (2012). Diagnostic utility

and factor structure of the PTSD Checklist in older adults. International Psychogeriatrics /IPA, 24(10), 1684�1696.

Powers, M. S., & Chester, J. A. (2014). Effects of stress, acute alcohol treatment, or both on

pre-pulse inhibition in high- and low-alcohol preferring mice. Alcohol (Fayetteville, N.Y.), 48

(2), 113�122.Prasad, C., & Prasad, A. (1995). A relationship between increased voluntary alcohol preference

and basal hypercorticosteronemia associated with an attenuated rise in corticosterone out-

put during stress. Alcohol (Fayetteville, N.Y.), 12(1), 59�63.Sartor, C. E., McCutcheon, V. V., Pommer, N. E., Nelson, E. C., Grant, J. D., Duncan, A. E., . . .

Heath, A. C. (2011). Common genetic and environmental contributions to post-traumatic

stress disorder and alcohol dependence in young women. Psychological Medicine, 41(7),

1497�1505.


179

Schelling, G., Briegel, J., Roozendaal, B., Stoll, C., Rothenhausler, H. B., & Kapfhammer, H. P.

(2001). The effect of stress doses of hydrocortisone during septic shock on posttraumatic

stress disorder in survivors. Biological Psychiatry, 50(12), 978�985.Sher, K. J., & Levenson, R. W. (1982). Risk for alcoholism and individual differences in the

stress-response-dampening effect of alcohol. Journal of Abnormal Psychology, 91(5),

350�367.

Shivani, R., Goldsmith, R. J., & Anthenelli, R. M. (2002). Alcoholism and psychiatric disorders -Diagnostic challenges. Alcohol Research & Health: The Journal of the National Institute on

Alcohol Abuse and Alcoholism, 26(2), 90�98.

Sinha, R., Robinson, J., & O’Malley, S. (1998). Stress response dampening: Effects of genderand family history of alcoholism and anxiety disorders. Psychopharmacology (Berl), 137(4),

311�320.

Stahre, M., Roeber, J., Kanny, D., Brewer, R. D., & Zhang, X. (2014). Contribution of excessive

alcohol consumption to deaths and years of potential life lost in the United States.Preventing Chronic Disease, 11, E109.

Stephens, M. A., & Wand, G. (2012). Stress and the HPA axis: Role of glucocorticoids in alco-

hol dependence. Alcohol Res, 34(4), 468�483.

Stewart, R. B., Gatto, G. J., Lumeng, L., Li, T. K., & Murphy, J. M. (1993). Comparison ofalcohol-preferring (P) and nonpreferring (NP) rats on tests of anxiety and for the anxiolytic

effects of ethanol. Alcohol (Fayetteville, N.Y.), 10(1), 1�10.

Swerdlow, N. R., Braff, D. L., & Geyer, M. A. (2016). Sensorimotor gating of the startle reflex:What we said 25 years ago, what has happened since then, and what comes next. Journal

of Psychopharmacology (Oxford, England), 30(11), 1072�1081.

Vengeliene, V., Siegmund, S., Singer, M. V., Sinclair, J. D., Li, T. K., & Spanagel, R. (2003). A

comparative study on alcohol-preferring rat lines: Effects of deprivation and stress phaseson voluntary alcohol intake. Alcoholism, Clinical and Experimental Research, 27(7),

1048�1054.

Vieweg, W. V., Julius, D. A., Fernandez, A., Beatty-Brooks, M., Hettema, J. M., & Pandurangi,

A. K. (2006). Posttraumatic stress disorder: Clinical features, pathophysiology, and treat-ment. The American Journal of Medicine, 119(5), 383�390.

Wand, G. S., Mangold, D., Ali, M., & Giggey, P. (1999). Adrenocortical responses and family

history of alcoholism. Alcoholism, Clinical and Experimental Research, 23(7), 1185�1190.

Whitaker, A. M., Farooq, M. A., Edwards, S., & Gilpin, N. W. (2016). Post-traumatic stressavoidance is attenuated by corticosterone and associated with brain levels of steroid recep-

tor co-activator-1 in rats. Stress (Amsterdam, Netherlands), 19(1), 69�77.

Yehuda, R. (2001). Biology of posttraumatic stress disorder. The Journal of Clinical Psychiatry,62(Suppl 17), 41�46.

Yehuda, R., Bierer, L. M., Schmeidler, J., Aferiat, D. H., Breslau, I., & Dolan, S. (2000). Low

cortisol and risk for PTSD in adult offspring of holocaust survivors. The American Journal of

Psychiatry, 157(8), 1252�1259.Zimmermann, U., Spring, K., Wittchen, H. U., & Holsboer, F. (2004). Effects of ethanol admin-

istration and induction of anxiety-related affective states on the acoustic startle reflex in

sons of alcohol-dependent fathers. Alcoholism, Clinical and Experimental Research, 28(3),

424�432.Zoladz, P. R., Fleshner, M., & Diamond, D. M. (2012). Psychosocial animal model of PTSD

produces a long-lasting traumatic memory, an increase in general anxiety and PTSD-like

glucocorticoid abnormalities. Psychoneuroendocrinology, 37(9), 1531�1545.


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