Differences In Anxiety-like Behavior Research Articles

Comfort Therapy with Companionship Improves Learning Memory and Reduces Hyperalgesia in Sickle Mice

Chronic and unpredictable acute pain coexist with cognitive dysfunction in sickle cell disease (SCD). Managing chronic pain is crucial, though efforts are complicated by both physiological and affective contributors to pain. The affective state, which is severely impacted by the environment including stigma and social isolation, plays a substantial role in pain perception and may further exacerbate psychological factors. Therefore, we examined if companionship and social isolation influence cognitive function and pain in SCD. In the present study, we examined the effects of social isolation on hyperalgesia, learning memory, and anxiety in humanized transgenic homozygous BERK mouse model of SCD. At ~3.5 months of age, BERK male mice were paired with age-matched female BERK companions (1 male + 1 female/cage; called companion group) and another group of BERK males were placed into isolation (one male/cage; called isolation group) for ~14 months. Isolation and companion groups were maintained in general housing conditions in the same room. Both groups were assessed for body weight, hyperalgesia and cognitive behaviors. Mechanical hyperalgesia was assessed by counting paw withdrawal frequency (PWF) following 10 applications of a 1.0 g von Frey monofilament (Semmes Weinstein, Stoelting, Wood Dale, IL, USA) to the plantar surface of the hind paw. Cold hyperalgesia was assessed following placement of mice onto a 4°C cold plate chamber (Stoelting) and by measuring PWF over a 2-minute period. Musculoskeletal hyperalgesia was measured by testing grip force of each mouse's peak forepaw grip to a computerized grip force meter (SA Maier, Milwaukee, WI, USA) and normalizing by body weight. The cognitive behavioral assessment consisted of an open field test to assess anxiety-related behaviors, which measured time spent and number of crosses through a central region. Working memory was assessed using novel object recognition and novel placement recognition tests to measure discrimination of novel objects and location. Data are shown as mean ± SEM and comparisons between companionship and isolation groups were performed using unpaired, two-tailed T-tests to determine statistical significance (P<0.05) We observed a significant increase in the body weights of males housed with females ( Companion group) compared to males in isolation (p<0.05). It is likely that males living with a companion were eating more compared to those under isolation. Isolated male sickle mice experience greater hyperalgesia than male mice housed with a female companion. Isolation induces greater PWF to mechanical (P<0.05) and cold (P<0.005) stimuli, indicating exacerbated hypersensitivity to mechanical and cold stimuli. Spontaneous, non-evoked musculoskeletal hyperalgesia was not significantly altered by isolation (P>0.05). Isolation also appeared to impact working and learning memory. Novel object recognition and novel object placement tests revealed reduced discrimination ratios in isolated mice (~25%, P<0.05 and ~25%, P<0.05), which are suggestive of impaired learning and memory function compared to mice with companionship. Open field test showed no significant difference (P>0.05) between isolation and companionship groups in time spent and number of crosses in the open field center area, indicating no detectable differences in anxiety-like behaviors. According to cognitive tests, mice in companionship showed greater novel object and place detection and greater cognitive ability compared to those in isolation. For the first time we show the causal role of social isolation on hyperalgesia and memory in a humanized mouse model of SCD. “ Comfort therapy” with companionship can ameliorate the perception of pain through the higher brain centres. It is also likely that mice in companionship eat more as evinced by a significant increase in their weight, which may provide additional comfort and meet the increased nutritional/calorie demands of SCD due to altered metabolism. Our observations suggest that “ comfort therapy” with improved living conditions and reducing isolation and loneliness may improve pain-related outcomes in SCD.

Decreased anxiety-like behavior in a selectively bred high nicotine-preferring rat line

Genetic vulnerability contributes significantly to the individual variability observed in nicotine dependence. Selective breeding for sensitivity to a particular effect of abused drugs has produced rodent lines useful for studying genetic vulnerability to drug addiction. Previous research showed that anxiety-related personality traits are associated with nicotine dependence. Therefore, we examined the differences in anxiety-like behavior between a high nicotine-preferring rat line and their controls. At the beginning of the study, all rats, naïve to any drug, were exposed sequentially to open field arena, marble-burying and elevated plus-maze paradigms. In the second step, all rats received nicotine in drinking water for 7 weeks. Behavioral tests were rerun on the final 2 weeks of chronic nicotine treatment. Elevated plus-maze testings under basal condition and during chronic nicotine treatment showed that the time spent on the open arms, preference for being in the open arms, and the latency to enter the closed arms were higher, whereas open arm avoidance index was lower in nicotine-preferring rats compared to the controls. In the open field test, nicotine-preferring rats spent longer time in the central zone and excreted less fecal pellets; they buried less marbles in the marble-burying test. These findings indicate a lower level of anxiety-like behavior in nicotine-preferring rat line under basal conditions and during chronic nicotine treatment. We conclude that lower anxiety level in nicotine-preferring rat line is consistent with novelty-seeking personality type and may increase vulnerability to nicotine dependence in this rat line.

Structural brain abnormalities in endothelial nitric oxide synthase-deficient mice revealed by high-resolution magnetic resonance imaging.

Endothelial nitric oxide synthase (eNOS) produces nitric oxide, which is essential for a variety of physiological functions in the brain. Previous work has demonstrated the detrimental effects of eNOS deficiency on brain function in male eNOS knockout (eNOS KO) mice. However, the effect of eNOS deficiency on brain structure and any association between these effects and sex is unknown. This study used three-dimensional high-resolution ex vivo magnetic resonance imaging and behavioral tests of anxiety and cognitive performance to investigate structure-function relationships in the brain of female and male eNOS KO mice in young adulthood. While there were no differences in anxiety-like behavior or locomotion, there was a sex-specific deficit in contextual fear memory retention in male, but not in female, eNOS mice compared to wild-type controls. Moreover, we found that eNOS deficiency induced changes in multiple brain regions that are involved in learning and fear memory including the hippocampus, amygdala, hypothalamus, and areas of the cortex. Several of these MRI-detectable neuroanatomical changes were dependent on sex. The observation that eNOS deficiency impacts brain structure at an early age demonstrates the importance of eNOS for healthy brain development.

Type 1 Corticotropin-Releasing Factor Receptor Differentially Modulates Neurotransmitter Levels in the Nucleus Accumbens of Juvenile versus Adult Rats.

Adversity is particularly pernicious in early life, increasing the likelihood of developing psychiatric disorders in adulthood. Juvenile and adult rats exposed to social isolation show differences in anxiety-like behaviors and significant changes in dopamine (DA) neurotransmission in the nucleus accumbens (NAc). Brain response to stress is partly mediated by the corticotropin-releasing factor (CRF) system, composed of CRF and its two main receptors, CRF-R1 and CRF-R2. In the NAc shell of adult rats, CRF induces anxiety-like behavior and changes local DA balance. However, the role of CRF receptors in the control of neurotransmission in the NAc is not fully understood, nor is it known whether there are differences between life stages. Our previous data showed that infusion of a CRF-R1 antagonist into the NAc of juvenile rats increased DA levels in response to a depolarizing stimulus and decreased basal glutamate levels. To extend this analysis, we now evaluated the effect of a CRF-R1 antagonist infusion in the NAc of adult rats. Here, we describe that the opposite occurred in the NAc of adult compared to juvenile rats. Infusion of a CRF-R1 antagonist decreased DA and increased glutamate levels in response to a depolarizing stimulus. Furthermore, basal levels of DA, glutamate, and γ-Aminobutyric acid (GABA) were similar in juvenile animals compared to adults. CRF-R1 protein levels and localization were not different in juvenile compared to adult rats. Interestingly, we observed differences in the signaling pathways of CRF-R1 in the NAc of juveniles compared to adult rats. We propose that the function of CRF-R1 receptors is differentially modulated in the NAc according to life stage.

Bdnf loss affects activity, sociability, and anxiety-like behaviour in zebrafish

Brain-derived neurotropic factor (BDNF) has established roles in neuronal survival and differentiation, in synaptic plasticity, and in neurotransmitters release. Several lines of evidence suggest that variations in BDNF might alter behaviour and contribute to neurobehavioural disorders. We investigated the functional effects of BDNF loss on behaviour by phenotyping a recently-generated CRISPR/Cas9 bdnf-/- zebrafish line through a battery of behavioural assays. Results of two behavioural tests suggested higher levels of locomotor activity in bdnf-/- zebrafish compared to bdnf+/+ zebrafish, in spite of similar swimming capacities observed in the two lines in a swim tunnel. bdnf-/- zebrafish also displayed higher levels of attraction towards a social stimulus compared to wild-type zebrafish, suggesting an effect of BDNF on sociability. Last, in a scototaxis test, we found evidence of potential differences in anxiety-like behaviour between the two lines. Our study supports an effect of BDNF on several behavioural traits, in line with early studies in mutant rodent models and in humans, suggesting the possibility to use the zebrafish to investigate diseases that involve alteration in BDNF levels.

Fear Extinction-Based Inter-Individual and Sex Differences in Pain-Related Vocalizations and Anxiety-like Behaviors but Not Nocifensive Reflexes.

Inter-individual and sex differences in pain responses are recognized but their mechanisms are not well understood. This study was intended to provide the behavioral framework for analyses of pain mechanisms using fear extinction learning as a predictor of phenotypic and sex differences in sensory (mechanical withdrawal thresholds) and emotional-affective aspects (open field tests for anxiety-like behaviors and audible and ultrasonic components of vocalizations) of acute and chronic pain. In acute arthritis and chronic neuropathic pain models, greater increases in vocalizations were found in females than males and in females with poor fear extinction abilities than females with strong fear extinction, particularly in the neuropathic pain model. Female rats showed higher anxiety-like behavior than males under baseline conditions but no inter-individual or sex differences were seen in the pain models. No inter-individual and sex differences in mechanosensitivity were observed. The data suggest that vocalizations are uniquely suited to detect inter-individual and sex differences in pain models, particularly in chronic neuropathic pain, whereas no such differences were found for mechanosensitivity, and baseline differences in anxiety-like behaviors disappeared in the pain models.

Anxiety-related defensive behavioral responses in mice selectively bred for High and Low Activity.

High and Low Activity strains of mice (displaying low and high anxiety-like behavior, respectively) with 7.8-20 fold differences in open-field activity were selected and subsequently inbred to use as a genetic model for studying anxiety-like behavior in mice (DeFries et al., 1978, Behavior Genetics, 8:3-13). These strains exhibited differences in other anxiety-related behaviors as assessed using the light-dark box, elevated plus-maze, mirror chamber, and elevated square-maze tests (Henderson et al., 2004, Behavior Genetics, 34: 267-293). The purpose of these experiments was three-fold. First, we repeated a 6-day behavioral battery using updated equipment and software to confirm the extreme differences in anxiety-like behaviors. Second, we tested novel object exploration, a measure of anxiety-like behavior that does not rely heavily on locomotion. Third, we conducted a home cage wheel running experiment to determine whether these strains differ in locomotor activity in a familiar, home cage environment. Our behavioral test battery confirmed extreme differences in multiple measures of anxiety-like behaviors. Furthermore, the novel object test demonstrated that the High Activity mice exhibited decreased anxiety-like behaviors (increased nose pokes) compared to Low Activity mice. Finally, male Low Activity mice ran nearly twice as far each day on running wheels compared to High Activity mice, while female High and Low Activity mice did not differ in wheel running. These results support the idea that the behavioral differences between High and Low Activity mice are likely to be due to anxiety-related factors and not simply generalized differences in locomotor activity.

Loss of Nociceptin/Orphanin FQ peptide receptor protects against traumatic brain injury (TBI)‐induced deficits in male and female rats

Introduction : Traumatic brain injury (TBI) is a leading cause of death and disability in the United States and often chronically affects mental and physical health and overall quality of life. We previously reported that acute treatment of blast TBI with a Nociceptin/OrphaninFQ (N/OFQ) peptide receptor (NOP) antagonist improved vestibulomotor deficits in male rats, corresponding to TBI-induced increases in NOP and its endogenous neuropeptide N/OFQ. The goal of this study is to determine whether the absence of NOP protects against neurological and behavioral sequelae of TBI in male and female KO rats compared to WT. Methods Male and female Wistar NOP receptor knockout (NOP KO) and wildtype (WT) rats received either a sham craniotomy, mild TBI (mTBI) or moderate TBI (ModTBI) controlled cortical impact (CCI) to the left cerebral hemisphere. Injury severity and recovery were assessed using modified neurological severity score (mNSS) on days 1 and 8 post-TBI. Vestibulomotor function was determined using the rotarod. Nociceptive sensitivity to mechanical and thermal stimuli were determined by measuring hind paw withdrawal threshold (PWT) to plastic filaments and by measuring tail flick latency (TFL) from radiant heat, respectively, prior to injury (baseline) and on days 2, 4, and 7 post-TBI. The presence of anxiety-like symptoms was assessed using the elevated plus maze (EPM) on day 7 post-TBI. Data were analyzed by two-way ANOVA with or without repeated measures (as appropriate). Results Rats of both genotypes and sexes showed complete neurological recovery (mNSS<1) following mTBI, and partial recovery following ModTBI by day 8. Mild and ModTBI produced significant vestibular deficits in rat rotarod performance on days 1-8 post-TBI in WT male (n=7-8). In WT females (n=8), ModTBI produced vestibular deficits on days 1-7, whereas mTBI only produced vestibular deficits on days 1-4. Interestingly, neither male (n=5-6) nor female (n=3) mTBI NOP KO rats exhibited vestibulomotor deficits. ModTBI caused significant vestibular deficits only on day 1 post-TBI in male and female NOP KO rats. Rotarod performance in WT females was significantly worse than KO females on days 2-4 post TBI following moderate injury (*p<0.05), and on days 4-7 following mild injury (*p<0.05). WT males (n=7-8) and females (n=8) exhibited thermal hyperalgesia and mechanical allodynia throughout the study, with little difference between mild and moderate TBI groups. KO males (n=3) developed no thermal hyperalgesia after either mild or ModTBI. Only ModTBI rats developed mechanical allodynia, and it lasted throughout the study. KO females (n=3) showed both thermal and mechanical hypersensitivity on day 2 and only mechanical hypersensitivity on day 4. No differences in anxiety-like behaviors were found between any of the groups. Conclusion The N/OFQ-NOP system contributes to vestibular deficits and hyperalgesia associated with TBI; the absence of NOP protects against TBI-induced vestibulomotor deficits and nociceptive hypersensitivity.

Maternal separation in rats induces neurobiological and behavioral changes on the maternal side

The time after parturition is a sensitive period for mothers where they are prone to develop psychopathological symptoms. Studies investigating dams after separation from their pups (maternal separation, MS) showed that MS induces alterations similar to postpartum depression. This study aims to give further details on affected behavior and neurobiology of dams after MS. MS in rats from postnatal day 2–20 over four hours daily was performed. Upon reunion, maternal behavior, and ultrasonic vocalization (USV) of dams were measured. On the day of weaning, dams were tested for anxiety-like behavior in the elevated-plus-maze and marble burying test. Then Morc1 mRNA in the medial prefrontal cortex and Nr3c1 encoding the glucocorticoid receptor mRNA in the hippocampus were measured using real-time PCR to examine possible neurobiological correlates in psychopathology and social behavior. GABA and glutamate serum levels were analyzed by high-performance liquid chromatography as peripheral markers for stress-induced psychopathology. MS in dams increased maternal care towards pups even though both groups show high levels of maternal behavior even in late lactation. Furthermore, the emission of 50-kHz and 22-kHz USVs increased significantly. No differences in anxiety-like behavior were detected. MS further reduced Morc1 but not Nr3c1 expression. Serum GABA but not glutamate levels were significantly increased in separated dams. This study reinforces the benefit of investigating dams after MS for studying postpartum stress. Subclinical markers mainly connected to depression, namely Morc1 and GABA, proved to be useful allowing for earlier detection of symptoms of critical postpartum stress.

The circadian gene Cryptochrome 2 influences stress-induced brain activity and depressive-like behavior in mice.

Cryptochrome 2 (Cry2) is a core clock gene important for circadian regulation. It has also been associated with anxiety and depressive-like behaviors in mice, but the previous findings have been conflicting in terms of the direction of the effect. To begin to elucidate the molecular mechanisms of this association, we carried out behavioral testing, PET imaging, and gene expression analysis of Cry2-/- and Cry2+/+ mice. Compared to Cry2+/+ mice, we found that Cry2-/- mice spent less time immobile in the forced swim test, suggesting reduced despair-like behavior. Moreover, Cry2-/- mice had lower saccharin preference, indicative of increased anhedonia. In contrast, we observed no group differences in anxiety-like behavior. The behavioral changes were accompanied by lower metabolic activity of the ventro-medial hypothalamus, suprachiasmatic nuclei, ventral tegmental area, anterior and medial striatum, substantia nigra, and habenula after cold stress as measured by PET imaging with a glucose analog. Although the expression of many depression-associated and metabolic genes was upregulated or downregulated by cold stress, we observed no differences between Cry2-/- and Cry2+/+ mice. These findings are consistent with other studies showing that Cry2 is required for normal emotional behavior. Our findings confirm previous roles of Cry2 in behavior and extend them by showing that the effects on behavior may be mediated by changes in brain metabolism.

Vendor differences in anxiety-like behaviors in female and male Sprague Dawley rats

Although Sprague Dawley outbred rats are commonly used in behavioral, physiological, and pharmacological studies, dramatic differences in responses may emerge from rats obtained from different suppliers even when sex, age, and environmental conditions are maintained constant. In the present study, we compared behavioral responses on three tests related to anxiety of Sprague Dawley female and male rats obtained from three different vendors in the United States: Charles River, Envigo, and Taconic. All rats were tested in the open field, light-dark box, and elevated zero maze. We found reduced time spent in the center area of the open field and decreased light compartment duration in the light-dark box test in female and male rats from Taconic compared to Charles River and Envigo rats, suggesting anxiety-like behaviors differ between the three vendors. No vendor differences were found on performance in the elevated zero maze. Furthermore, the contribution of stress hormones to vendor differences was examined by measuring serum corticosterone levels in rats 30 min after exposure to the elevated zero maze. There were no vendor differences in corticosterone levels, suggesting that endogenous levels of stress hormones most likely did not contribute to vendor differences in anxiety-like behaviors. Collectively, these findings highlight the importance of vendor selection of the Sprague Dawley stock for research involving behavioral tests related to anxiety.

Anxiety-like behaviour is regulated independently from sex, mating status and the sex peptide receptor in Drosophila melanogaster

Sex differences in anxiety-related behaviours have been documented in many animals and are notable in human populations. A major goal in behaviour research is to understand why and how sex differences in cognitive-emotional states like anxiety arise and are regulated throughout life. Anxiety allows individuals to detect and respond to threats. Mating is a candidate regulator for anxiety because threats are likely to change, often in sex-specific ways, when individuals shift to a postmating reproductive state. However, we know little about how mating mediates anxiety-related behaviour in males and females, or about how males might influence female anxiety via seminal proteins transferred during mating. To address this gap, we examined anxiety-related behaviour in the fruit fly Drosophila melanogaster , an emerging model animal for anxiety, with respect to sex, mating and sex peptide, a seminal protein known to modulate a host of female postmating responses in fruit flies. We assayed anxiety-like behaviour using the open-field assay to assess individual avoidance of the interior of an arena (‘wall-following’ behaviour). We found sex differences in activity level, but no evidence for sex differences in wall-following behaviour. We found no effects of mating in either sex, or of the presence of the sex peptide receptor in females, on wall following. Our results suggest that anxiety is not one of the cognitive-emotional states regulated by mating and sex peptide in fruit flies, and that researchers need an alternative model for sex differences in anxiety. • Many animals display anxiety, but few studies have compared males and females. • In fruit flies, we found no sex differences in anxiety-like behaviour. • Mating could modulate anxiety, directly or via male ejaculate proteins. • We found that anxiety was independent from mating and the sex peptide protein. • Anxiety is not part of the postmating behavioural shift in fruit flies.

Trait Anxiety Mediated by Amygdala Serotonin Transporter in the Common Marmoset.

High trait anxiety is associated with altered activity across emotion regulation circuitry and a higher risk of developing anxiety disorders and depression. This circuitry is extensively modulated by serotonin. Here, to understand why some people may be more vulnerable to developing affective disorders, we investigated whether serotonin-related gene expression across the brain's emotion regulation circuitry may underlie individual differences in trait anxiety using the common marmoset (Callithrix jacchus, mixed sexes) as a model. First, we assessed the association of region-specific expression of the serotonin transporter (SLC6A4) and serotonin receptor (HTR1A, HTR2A, HTR2C) genes with anxiety-like behavior; and second, we investigated their causal role in two key features of the high trait anxious phenotype: high responsivity to anxiety-provoking stimuli and an exaggerated conditioned threat response. While the expression of the serotonin receptors did not show a significant relationship with anxiety-like behavior in any of the targeted brain regions, serotonin transporter expression, specifically within the right ventrolateral prefrontal cortex (vlPFC) and most strongly in the right amygdala, was associated positively with anxiety-like behavior. The causal relationship between amygdala serotonin levels and an animal's sensitivity to threat was confirmed via direct amygdala infusions of a selective serotonin reuptake inhibitor (SSRI), citalopram. Both anxiety-like behaviors, and conditioned threat-induced responses were reduced by the blockade of serotonin reuptake in the amygdala. Together, these findings provide evidence that high amygdala serotonin transporter expression contributes to the high trait anxious phenotype and suggest that reduction of threat reactivity by SSRIs may be mediated by their actions in the amygdala.SIGNIFICANCE STATEMENT Findings here contribute to our understanding of how the serotonin system underlies an individual's expression of threat-elicited negative emotions such as anxiety and fear within nonhuman primates. Exploration of serotonergic gene expression across brain regions implicated in emotion regulation revealed that serotonin transporter gene expression in the ventrolateral prefrontal cortex (vlPFC) and most strongly in the amygdala, but none of the serotonin receptor genes, were predictive of interindividual differences in anxiety-like behavior. Targeting of amygdala serotonin reuptake with selective serotonin reuptake inhibitors (SSRIs) confirmed the causal relationship between amygdala serotonin transporter and an animal's sensitivity to threat by reversing expression of two key features of the high trait-like anxiety phenotype: high responsivity to anxiety-provoking uncertain threat and responsivity to certain conditioned threat.

Determining nicotine-related behavior changes in juvenile female rats through long-term maternal nicotine exposure.

Nicotine replacement therapy (NRT) has been developed as a drug therapy for smoking cessation and has been considered a safe alternative to smoking during pregnancy. However, the effects of long-term nicotine exposure via NRT on the fetus are still being debated. Here, we determined the effects of long-term maternal nicotine exposure in gestation and lactation on nicotine-related behavior and drug vulnerability in dams and offspring rats. To expose long-term nicotine, on gestation day 14, pregnant rats were implanted with osmotic minipumps releasing nicotine tartrate (6 mg/kg/day, subcutaneously, equivalent to 2 mg nicotine-freebase) for 28 days. The concentration of cotinine in blood was 373.0 ± 109.0 ng/ml in dams and 12.50 ± 1.19 ng/ml in offspring rats. In dams, we found no significant differences in anxiety-like behaviors and various maternal behaviors such as touching, sniffing, pup licking, laying on pups, and retrieval between saline- and nicotine-exposed groups. Adolescent offspring female rats showed no significant differences in anxiety-like behavior and forced alcohol consumption between saline- and nicotine-exposed groups. Nicotine-exposed offspring rats showed more increased nicotine aversion than saline-exposed groups, but the effect was disturbed in the forced alcohol consumption condition on the first day of the nicotine consumption test. Taken together, these results suggest that, in the last gestation and lactation period corresponding to the second and third trimester of human pregnancy, long-term maternal nicotine exposure has a minor effect on dam and female offspring health and does not involve serious pathological changes in rat offspring, despite the presence of nicotine in their blood.

Sex differences in anxiety-like behaviors in rats

The use of animal models for behavioral and pharmaceutical testing is employed in many different fields of research but often relies solely on male animals. When females are included, the existing literature frequently offers inconsistent results regarding the effects of sex and/or estrous cycle on anxiety-like behaviors. Our current study sought to establish baseline or normative behaviors in three commonly employed tests of anxiety-like behavior, and determine any sex or cycle differences. Anxiety-like behaviors in male and naturally-cycling female Sprague-Dawley rats were assessed using elevated plus maze, open field, and a social interaction/avoidance paradigm. Female rats were examined once daily to determine their stage of estrous. Results from the elevated plus maze but not the open field showed that female rats spent significantly more time in open areas than did male rats; however, there was no effect of estrous cycle stage. The social avoidance test revealed that female rats spent significantly more time in the interaction zone with an empty wire mesh cage (novel object), but there was no sex difference in time spent with an age- and sex- matched target rat. Females often exhibited greater locomotion as compared to males in social and non-social tests, but this was not related to primary anxiety measures in these tests. Overall, our findings indicate that outcomes differ in tests of anxiety-like behaviors, highlighting sex differences in the expression of anxiety-like behaviors that depend on the test employed. Importantly, the lack of estrous cycle effects suggest that for these anxiety-based tests, female Sprague-Dawley rats could be collapsed across the cycle phases to facilitate the inclusion of females in future behavioral experiments.

Ultrasonic vocalization sex differences in 5-HT1A-R deficient mouse pups: Predictive phenotypes associated with later-life anxiety-like behaviors

Anxiety disorders affect nearly twice as many women as men. However, little is known regarding sex-dependent developmental behavioral differences and whether there is an association with later life anxiety disorders. The present study assessed the developmental-behavioral milestones (DBMs) and their relationship with later life anxiety-like behaviors by comparing postnatal ultrasonic vocalizations (USVs) with open field (OF), elevated plus maze (EPM), and light/dark (LD) anxiety test outcomes using the serotonin 1A receptor knockout (KO) mouse model of anxiety. The USVs and DBMs (i.e., grasping, righting, and startle reflexes) were examined on postnatal day 6 (P6), P8, and P10. Adult anxiety-like behaviors were examined on P60 to compare the genotype and sex-dependent differences in anxiety-like behaviors and to correlate them with the USVs. The total number of USVs observed on P8 correlated with later life anxiety-like behaviors in a genotype-, age-, and sex-dependent manner. Interestingly, female KO (KOF) mice exhibited elevated levels of anxiety-like behavior within the OF, EPM, and LD tests. Additionally, an investigation of the USV subtypes, as well as USV sequence structure and repertoire variation, revealed that the KOF mice produced less complex USVs and complex USV-containing sequences on P10. The present study provides an intriguing, predictive “P8/10-USV-to-P60” anxiety-like behavioral model that may prove useful in future characterization, psychopharmacology, and drug rescue studies directed towards sex-specific anxiety treatment.

Exploratory, cognitive, and depressive-like behaviors in adult and pediatric mice exposed to controlled cortical impact

ObjectiveSequelae of behavioral impairments associated with human traumatic brain injury (TBI) include neurobehavioral problems. We compared exploratory, cognitive, and depressive-like behaviors in pediatric and adult male mice exposed to controlled cortical impact (CCI).MethodsPediatric (21 to 25 days old) and adult (8 to 12 weeks old) male C57Bl/6 mice underwent CCI at a 2-mm depth of deflection. Hematoxylin and eosin staining was performed 3 to 7 days after recovery from CCI, and injury volume was analyzed using ImageJ. Neurobehavioral characterization after CCI was performed using the Barnes maze test (BMT), passive avoidance test, open-field test, light/dark test, tail suspension test, and rotarod test. Acutely and subacutely (3 and 7 days after CCI, respectively), CCI mice showed graded injury compared to sham mice for all analyzed deflection depths.ResultsTime-dependent differences in injury volume were noted between 3 and 7 days following 2-mm TBI in adult mice. In the BMT, 2-mm TBI adults showed spatial memory deficits compared to sham adults (P<0.05). However, no difference in spatial learning and memory was found between sham and 2-mm CCI groups among pediatric mice. The open-field test, light/dark test, and tail suspension test did not reveal differences in anxiety-like behaviors in both age groups.ConclusionOur findings revealed a graded injury response in both age groups. The BMT was an efficient cognitive test for assessing spatial/non-spatial learning following CCI in adult mice; however, spatial learning impairments in pediatric mice could not be assessed.

Affective Behavior in Withdrawal Seizure-Prone and Withdrawal Seizure-Resistant Mice during Long-Term Alcohol Abstinence.

While the acute alcohol withdrawal syndrome has been well characterized both in human clinical studies and in experimental animals, much less is known regarding long-term affective disturbances that can sometimes persist during protracted abstinence. Nevertheless, since relapse often occurs long after acute detoxification and may be predicted by persistent affective disruption, a better understanding of the long-term behavioral consequences of prior alcohol dependence may lead to improved strategies for relapse prevention. Male and female Withdrawal Seizure-Prone and Withdrawal Seizure-Resistant mice from the second selection replicate (WSP-2, WSR-2) were exposed to a 10-day chronic-intermittent ethanol vapor protocol (CIE) or plain air and then tested repeatedly on the sucrose preference test (SPT), marble burying test (MBT), and the light-dark box test (LDT) over 7weeks of (forced) abstinence. While WSP and WSR mice differed significantly on tests of anxiety-like behavior (LDT, MBT), we found little evidence for long-term affective disruption following CIE in either line. The major exception was in the LDT, in that WSP but not WSR mice displayed longer latencies to enter the light compartment following CIE relative to air-controls. Selective breeding for acute withdrawal severity has resulted in differences in anxiety-like behavior between WSP and WSR mice. In contrast, however, genes contributing to the severity of acute withdrawal convulsions appear to have little overlap with those predisposing to affective disruption during long-term abstinence.

Effect of dietary vitamin E on oxidative stress-related gene-mediated differences in anxiety-like behavior in inbred strains of mice

It has been reported that the degree of anxiety-like behavior differs between inbred strains of mice, and that this phenomenon was linked to the expression levels of the oxidative stress-related genes glyoxalase 1 (Glo1) and glutathione reductase 1 (Gsr) in the brain. Therefore, we investigated whether antioxidative activity in the brain affects the Glo1 and Gsr mRNA expressions and strain-dependent anxiety-like behavior using mice fed different amounts of vitamin E. First, we measured brain Glo1 and Gsr mRNA levels and evaluated the anxiety-like behaviors presented by C57BL/6J (B6) and DBA/2C (D2) mice. We demonstrated that D2 mice presented both significantly elevated Glo1 and Gsr mRNA levels as well as more prominent anxiety-like behavior in elevated plus-maze and open field tests. Next, we fed mice from these two strains either a control, vitamin E-free, or vitamin E-supplemented diet for four weeks. Plasma, liver, and brain α-tocopherol concentrations changed in a dose-dependent manner. However, neither brain Glo1 and Gsr mRNA levels nor anxiety-like behavior were affected by dietary vitamin E intake. These results demonstrated that while strain-dependent anxiety-like behavior in mice was related to oxidative stress-related gene expression, the regulatory mechanisms for these genes and anxiety-like behaviors were independent of antioxidative activity in the brain. Strain-dependent differences of the anxiety in mice are probably related to the anxiolytic effects of methylglyoxal, a substrate for Glo1 and Gsr.

Single Prolonged Stress as a Prospective Model for Posttraumatic Stress Disorder in Females

BackgroundSex plays an important role in susceptibility to stress triggered disorders. Posttraumatic Stress disorder (PTSD), a debilitating psychiatric disorder developed after exposure to a traumatic event, is two times more prevalent in women than men. However, the vast majority of animal models of PTSD, including single prolonged stress (SPS), were performed mostly with males.Objectives(1) Evaluate SPS as an appropriate model for PTSD in female rodents in terms of anxiety, depressive symptoms and changes of gene expression in the locus coeruleus; (2) Asses sex differences in SPS‐triggered changes in these measures; (3) Examine intranasal NPY as a potential early intervention for females.MethodsFemale rats were subjected to SPS and given either intranasal NPY or vehicle. Twelve and seven days later they were compared to unstressed controls on forced swim test (FST) and elevated plus maze (EPM) respectively. Changes in gene expression in the locus coeruleus (LC) were determined by quantitative RT‐PCR.Results and InterpretationSPS led to increased anxiety‐like behavior on EPM, and tended to raise depressive‐like behavior on FST. Following FST rats displayed elevated TH, CRHR1 and Y1R mRNA levels in the LC, consistent with increased activation of the noradrenergic system.The expression level of these mRNAs were unchanged following EPM. Intranasal NPY at the doses shown to be effective in males, did not prevent development of depressive or anxiety‐like behavior or molecular changes in the LC. SPS may be milder for females when compared to males, as they did not show despair or immobility as readily as males on the forced swim component of the SPS protocols. In addition, after SPS stressors females exhibited less immobility on FST than males, however there were little overall sex differences in anxiety‐like behavior on EPM.ConclusionsThe results indicate that while SPS could be an appropriate PTSD model for females, there are important sex differences, such as response to NPY, that need to be taken into account.Support or Funding InformationThis work was supported by the Office of the Assistant Secretary of Defense for Health Affairs through the DOD Department of Defense Broad Agency Announcement for Extramural Medical Research under Award No W81XWH‐16‐1‐0016 and by funds from the NYMC/Touro Bridge Funding Program.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.