Mechanisms of estradiol in fear circuitry: implications for sex differences in psychopathology

An investigation of the role of estradiol in fear reduction during a single session of exposure therapy

Research suggests that estradiol may moderate fear extinction. It is unclear whether these results generalize to exposure therapy. The aim of the current study was to determine whether estradiol moderates outcomes in exposure therapy among women with anxiety disorders. Participants were 35 women with a primary diagnosis of an anxiety disorder who participated in the study as part of routine care at an anxiety specialty clinic. Endogenous estradiol was assessed via saliva. They provided subjective distress ratings before (pre) and after (post) an exposure session, as well as after a brief delay (recall). Contrary to predictions, there were no significant differences in exposure outcomes between the high and low estradiol groups. However, among participants with primary obsessive-compulsive disorder (OCD), results were partially consistent with the hypotheses. Women with lower estradiol initially demonstrated more improvement in subjective distress from pre- to post-exposure, but after the delay, significantly greater distress (attenuated extinction recall). Results suggest that women with lower estradiol may respond less favorably to exposure therapy for OCD relative to women with higher estradiol. These findings await replication in larger samples with longer recall delays. Should replication occur, these results may inform the use of estradiol to augment exposure therapy.

Acute sleep deprivation reduces fear memories in male and female mice

Sleep problems are a prominent feature of mental health conditions including post-traumatic stress disorder (PTSD). Despite its potential importance, the role of sleep in the development of and/or recovery from trauma-related illnesses is not understood. Interestingly, there are reports that sleep deprivation immediately after a traumatic experience can reduce fear memories, an effect that could be utilized therapeutically in humans. While the mechanisms of this effect are not completely understood, one possible explanation for these findings is that immediate sleep deprivation interferes with consolidation of fear memories, rendering them weaker and more sensitive to intervention. Here, we allowed fear-conditioned mice to sleep immediately after fear conditioning during a time frame (18 hr) that includes and extends beyond periods typically associated with memory consolidation before subjecting them to 6 hr of sleep deprivation. Mice deprived of sleep with this delayed regimen showed dramatic reductions in fear during tests conducted immediately after sleep deprivation, as well as 24 hr later. This sleep deprivation regimen also increased levels of mRNA encoding brain-derived neurotrophic factor (BDNF), a molecule implicated in neuroplasticity, in the basolateral amygdala (BLA), a brain area implicated in fear and its extinction. These findings raise the possibility that the effects of our delayed sleep deprivation regimen are not due to disruption of memory consolidation, but instead are caused by BDNF-mediated neuroadaptations within the BLA that actively suppress expression of fear. Treatments that safely reduce expression of fear memories would have considerable therapeutic potential in the treatment of conditions triggered by trauma.

Neuroimaging of posttraumatic stress disorder in adults and youth: progress over the last decade on three leading questions of the field

Almost three decades have passed since the first posttraumatic stress disorder (PTSD) neuroimaging study was published. Since then, the field of clinical neuroscience has made advancements in understanding the neural correlates of PTSD to create more efficacious treatment strategies. While gold-standard psychotherapy options are available, many patients do not respond to them, prematurely drop out, or never initiate treatment. Therefore, elucidating the neurobiological mechanisms that define the disorder can help guide clinician decision-making and develop individualized mechanisms-based treatment options. To this end, this narrative review highlights progress made in the last decade in adult and youth samples on three outstanding questions in PTSD research: (1) Which neural alterations serve as predisposing (pre-exposure) risk factors for PTSD development, and which are acquired (post-exposure) alterations? (2) Which neural alterations can predict treatment outcomes and define clinical improvement? and (3) Can neuroimaging measures be used to define brain-based biotypes of PTSD? While the studies highlighted in this review have made progress in answering the three questions, the field still has much to do before implementing these findings into clinical practice. Overall, to better answer these questions, we suggest that future neuroimaging studies of PTSD should (A) utilize prospective longitudinal designs, collecting brain measures before experiencing trauma and at multiple follow-up time points post-trauma, taking advantage of multi-site collaborations/consortiums; (B) collect two scans to explore changes in brain alterations from pre-to-post treatment and compare changes in neural activation between treatment groups, including longitudinal follow up assessments; and (C) replicate brain-based biotypes of PTSD. By synthesizing recent findings, this narrative review will pave the way for personalized treatment approaches grounded in neurobiological evidence.

Role of estrogen in sex differences in memory, emotion and neuropsychiatric disorders

Estrogen regulates a wide range of neuronal functions in the brain, such as dendritic spine formation, remodeling of synaptic plasticity, cognition, neurotransmission, and neurodevelopment. Estrogen interacts with intracellular estrogen receptors (ERs) and membrane-bound ERs to produce its effect via genomic and non-genomic pathways. Any alterations in these pathways affect the number, size, and shape of dendritic spines in neurons associated with psychiatric diseases. Increasing evidence suggests that estrogen fluctuation causes changes in dendritic spine density, morphology, and synapse numbers of excitatory and inhibitory neurons differently in males and females. In this review, we discuss the role of estrogen hormone in rodents and humans based on sex differences. First, we explain estrogen role in learning and memory and show that a high estrogen level alleviates the deficits in learning and memory. Secondly, we point out that estrogen produces a striking difference in emotional memories in men and women, which leads them to display sex-specific differences in underlying neuronal signaling. Lastly, we discuss that fluctuations in estrogen levels in men and women are related to neuropsychiatric disorders, including schizophrenia, autism spectrum disorder (ASD), attention deficit hyperactivity disorder (ADHD), bipolar disorder (BPD), major depressive disorder (MDD), substance use disorder (SUD), and anxiety disorders.

Perinatal exposure to bisphenol A or S: Effects on anxiety-related behaviors and serotonergic system

Bisphenols, synthetic organic compounds used in the production of plastics, are an extremely abundant class of Endocrine Disrupting Chemicals, i.e., exogenous chemicals or mixtures of chemicals that can interfere with any aspect of hormone action. Exposure to BPs can lead to a wide range of effects, and it is especially dangerous if it occurs during specific critical periods of life. Focusing on the perinatal exposure to BPA or its largely used substitute BPS, we investigated the effects on anxiety-related behaviors and the serotonergic system, which is highly involved in controlling these behaviors, in adult mice. We treated C57BL/6J dams orally with a dose of 4 μg/kg body weight/day (i.e., EFSA TDI) of BPA or BPS dissolved in corn oil or with vehicle alone, at the onset of mating and continued treatment until the offspring were weaned. Adult offspring of both sexes performed the elevated plus maze and the open field tests. Then, we analyzed the serotonergic system in dorsal (DR) and median (MnR) raphe nuclei by immunohistochemical techniques. Behavioral tests highlighted alterations in BPA- and BPS-treated mice, suggesting different effects of the bisphenols exposure on anxiety-related behavior in males (anxiolytic) and females (anxiogenic). The analysis of the serotonergic system highlighted a sex dimorphism in the DR only, with control females showing higher values of serotonin immunoreactivity (5-HT-ir) than control males. BPA-treated males displayed a significant increase of 5-HT-ir in all analyzed nuclei, whereas BPS-treated males showed an increase in ventral DR only. In females, both bisphenols-treated groups showed a significant increase of 5-HT-ir in dorsal DR compared to the controls, and BPA-treated females also showed a significant increase in MnR.These results provide evidence that exposure during the early phases of life to BPA or BPS alters anxiety and the raphe serotonergic neurons in a sex-dependent manner.

The sexually divergent cFos activation map of fear extinction

Objective

Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder that can develop after experiencing or witnessing a traumatic event. Exposure therapy is a common treatment for PTSD, but it has varying levels of efficacy depending on sex. In this study, we aimed to compare the sexual dimorphism in brain activation during the extinction of fear conditioning in male and female rats by detecting the c-fos levels in the whole brain.

Methods

Thirty-two rats (Male: n = 16; Female: n = 16) were randomly separated into the extinction group as well as the non-extinction group, and fear conditioning was followed by extinction and non-extinction, respectively. Subsequently, brain sections from the sacrificed animal were performed immunofluorescence and the collected data were analyzed by repeated two-way ANOVAs as well as Pearson Correlation Coefficient.

Results

Our findings showed that most brain areas activated during extinction were similar in both male and female rats, except for the reuniens thalamic nucleus and ventral hippocampi. Furthermore, we found differences in the correlation between c-fos activation levels and freezing behavior during extinction between male and female rats. Specifically, in male rats, c-fos activation in the anterior cingulate cortex was negatively correlated with the freezing level, while c-fos activation in the retrosplenial granular cortex was positively correlated with the freezing level; but in female rats did not exhibit any correlation between c-fos activation and freezing level. Finally, the functional connectivity analysis revealed differences in the neural networks involved in extinction learning between male and female rats. In male rats, the infralimbic cortex and insular cortex, anterior cingulate cortex and retrosplenial granular cortex, and dorsal dentate gyrus and dCA3 were strongly correlated after extinction. In female rats, prelimbic cortex and basolateral amygdala, insular cortex and dCA3, and anterior cingulate cortex and dCA1 were significantly correlated.

Conclusion

These results suggest divergent neural networks involved in extinction learning in male and female rats and provide a clue for improving the clinical treatment of exposure therapy based on the sexual difference.

Predictors of clinical worsening during a discontinuation trial of serotonin reuptake inhibitors for obsessive compulsive disorder

OBJECTIVE

To explore predictors and moderators of clinical worsening during a double-blind trial in which patients with obsessive-compulsive disorder (OCD) were randomized to either continue or discontinue their Serotonin Reuptake Inhibitor (SRI) medication after achieving wellness from the addition of exposure and response prevention (EX/RP) therapy.

METHOD

The data came from a double-blind discontinuation trial that included N = 101 participants, 35 of whom were removed from the study due to clinical worsening. We first used LASSO logistic regression to identify which of the 34 potential baseline variables of interest (including demographics, diagnoses, other relevant clinical constructs, and specific genotypes), might moderate or predict this clinical worsening. Then logistic regression was used to examine which of these identified variables were significantly related to later clinical worsening. We verified the validity of our final prediction model using k-fold cross-validation.

RESULTS

There was one significant predictor of clinical worsening: In both groups, those with more past diagnoses had a greater likelihood of clinical worsening (p = .015). There were several moderators. Rates of clinical worsening were higher in the Discontinuation group compared to the Continuation group for participants who were taking a shorter half-life SRI (p = .044), were female (p = .022), had higher baseline levels of maladaptive metacognitions (p < .001), had fewer sleep problems at baseline (p = .001), and/or had more years of education (p < .001).

CONCLUSIONS

Our results identified several factors that may predict the development of clinical worsening in OCD patients discontinuing SRI medication following successful EX/RP treatment.

Chronic adolescent stress alters GR-FKBP5 interactions in the hippocampus of adult female rats

Chronic stress exposure during development can have lasting behavioral consequences that differ in males and females. More specifically, increased depressive behaviors in females, but not males, are observed in both humans and rodent models of chronic stress. Despite these known stress-induced outcomes, the molecular consequences of chronic adolescent stress in the adult brain are less clear. The stress hormone corticosterone activates the glucocorticoid receptor, and activity of the receptor is regulated through interactions with co-chaperones-such as the immunophilin FK506 binding proteins 5 (FKBP5). Previously, it has been reported that the adult stress response is modified by a history of chronic stress; therefore, the current study assessed the impact of chronic adolescent stress on the interactions of the glucocorticoid receptor (GR) with its regulatory co-chaperone FKBP5 in response to acute stress in adulthood. Although protein presence for FKBP5 did not differ by group, assessment of GR-FKBP5 interactions demonstrated that adult females with a history of chronic adolescent stress had elevated GR-FKBP5 interactions in the hippocampus following an acute stress challenge which could potentially contribute to a reduced translocation pattern given previous literature describing the impact of FKBP5 on GR activity. Interestingly, the altered co-chaperone interactions of the GR in the stressed female hippocampus were not coupled to an observable difference in transcription of GR-regulated genes. Together, these studies show that chronic adolescent stress causes lasting changes to co-chaperone interactions with the glucocorticoid receptor following stress exposure in adulthood and highlight the potential role that FKBP5 plays in these modifications. Understanding the long-term implications of adolescent stress exposure will provide a mechanistic framework to guide the development of interventions for adult disorders related to early life stress exposures.

The role of sex hormones, oral contraceptive use, and its parameters on visuospatial abilities, verbal fluency, and verbal memory

Sex hormones can cross the blood-brain barrier and access brain regions underlying higher-order cognition. Containing synthetic sex hormones, oral contraceptives (OC) have been found to modulate visuospatial and verbal abilities, though inconsistencies have been found in the literature. Among possible explanations, certain OC use parameters (progestin androgenicity, synthetic hormone levels, duration of use) have not received consistent consideration. Thus, the objectives were to (1) examine group differences between men, combined OC users, and naturally cycling women (NC women; not using OC) in visuospatial abilities, verbal fluency, and verbal memory and (2) investigate the contribution of endogenous and exogenous sex hormones on these effects. We also aimed to (3) identify OC use parameters relevant to cognitive outcomes. In total, 70 combined OC users, 53 early follicular (EF) women, 43 pre-ovulatory (PO) women, and 47 men underwent cognitive tests. Performance was compared based on hormonal milieus (OC, EF, PO, men) and OC users' contraceptive androgenicity (anti, low, high). Correlations between performance, hormone levels and OC use duration were also conducted. OC use dampened the sex difference that typically favors men in 3D visuospatial abilities, whereas its duration of use positively predicted verbal fluency. Androgenicity and hormone levels did not predict performance in any task. These results highlight the importance of considering OC use duration. Results also did not support a role for androgenicity in cognition. Importantly, combined OC use (including prolonged use) does not impair visuospatial, verbal, and memory functions in a healthy young sample.

Effects of oral contraceptives on intrusive memories: a secondary analysis of two studies using the trauma film paradigm in healthy women

Background: Women are more likely to develop post-traumatic stress disorder (PTSD) than men. Recent research suggests an impact of oral contraceptive (OC) intake on PTSD and intrusive memories, a hallmark symptom of PTSD. Although a majority of women use OCs at some point in their lives, the effects on PTSD pathogenesis are only poorly understood.Objective: In the current paper, we aimed to investigate the impact of OC intake on the acquisition and consolidation of intrusive memories in healthy women after watching a trauma film paradigm.Methods: We performed a secondary analysis of a pooled dataset (N = 437) of two previously conducted and published studies investigating the effect of oxytocin on the development of intrusive memories.Results: Women taking OCs showed an attenuated decline of intrusive memories over time after having watched the trauma film compared to naturally cycling women (F(2.75, 1167) = 3.79, p = .03, η p 2  = .01).Conclusion: These findings indicate that the intake of OCs is associated with the development of intrusive memories after a trauma film paradigm. This indication emphasizes the need to further investigate the complex impact of OCs and gonadal hormones on fear learning processes and PTSD.

Morphologic alterations of the fear circuitry: the role of sex hormones and oral contraceptives

Background

Endogenous sex hormones and oral contraceptives (OCs) have been shown to influence key regions implicated in fear processing. While OC use has been found to impact brain morphology, methodological challenges remain to be addressed, such as avoiding selection bias between OC users and non-users, as well as examining potential lasting effects of OC intake.

Objective

We investigated the current and lasting effects of OC use, as well as the interplay between the current hormonal milieu and history of hormonal contraception use on structural correlates of the fear circuitry. We also examined the role of endogenous and exogenous sex hormones within this network.

Methods

We recruited healthy adults aged 23-35 who identified as women currently using (n = 62) or having used (n = 37) solely combined OCs, women who never used any hormonal contraceptives (n = 40), or men (n = 41). Salivary endogenous sex hormones and current users' salivary ethinyl estradiol (EE) were assessed using liquid chromatography - tandem mass spectrometry. Using structural magnetic resonance imaging, we extracted surface-based gray matter volumes (GMVs) and cortical thickness (CT) for regions of interest of the fear circuitry. Exploratory whole-brain analyses were conducted with surface-based and voxel-based morphometry methods.

Results

Compared to men, all three groups of women exhibited a larger GMV of the dorsal anterior cingulate cortex, while only current users showed a thinner ventromedial prefrontal cortex. Irrespective of the menstrual cycle phase, never users exhibited a thicker right anterior insular cortex than past users. While associations with endogenous sex hormones remain unclear, we showed that EE dosage in current users had a greater influence on brain anatomy compared to salivary EE levels and progestin androgenicity, with lower doses being associated with smaller cortical GMVs.

Discussion

Our results highlight a sex difference for the dorsal anterior cingulate cortex GMV (a fear-promoting region), as well as a reduced CT of the ventromedial prefrontal cortex (a fear-inhibiting region) specific to current OC use. Precisely, this finding was driven by lower EE doses. These findings may represent structural vulnerabilities to anxiety and stress-related disorders. We showed little evidence of durable anatomical effects, suggesting that OC intake can (reversibly) affect fear-related brain morphology.

The impact of physical exercise on the consolidation of fear extinction memories

Based on the mechanisms of fear extinction, exposure therapy is the most common treatment for anxiety disorders. However, extinguished fear responses can reemerge even after successful treatment. Novel interventions enhancing exposure therapy efficacy are therefore critically needed. Physical exercise improves learning and memory and was also shown to enhance extinction processes. This study tested whether physical exercise following fear extinction training improves the consolidation of extinction memories. Sixty healthy men underwent a differential fearconditioning paradigm with fear acquisition training on day 1 and fear extinction training followed by an exercise or resting control intervention on day 2. On day 3, retrieval and reinstatement were tested including two additional but perceptually similar stimuli to explore the generalization of exercise effects. Exercise significantly increased heart rate, salivary alpha amylase, and cortisol, indicating successful exercise manipulation. Contrary to our expectations, exercise did not enhance but rather impaired extinction memory retrieval on the next day, evidenced by significantly stronger differential skin conductance responses (SCRs) and pupil dilation (PD). Importantly, although conditioned fear responses were successfully acquired, they did not fully extinguish, explaining why exercise might have boosted the consolidation of the original fear memory trace instead. Additionally, stronger differential SCRs and PD toward the novel stimuli suggest that the memory enhancing effects of exercise also generalized to perceptually similar stimuli. Together, these findings indicate that physical exercise can facilitate both the long-term retrievability and generalization of extinction memories, but presumably only when extinction was successful in the first place.

Inactivation of medial or lateral orbitofrontal cortex during fear extinction did not interfere with fear renewal

Hyperactive orbitofrontal cortical activation is commonly seen in patients of obsessive-compulsive disorder (OCD). Previous studies from our laboratory showed that for rats with aberrant activation of the orbitofrontal cortex (OFC) during the extinction phase, they were unable to use contexts as the reference for proper retrieval of fear memory during renewal test. This result supported the phenomenon that many OCD patients show poor regulation of fear-related behavior. Since there are robust anatomical connections of the OFC with the fear-circuit, we aim to further examine whether the OFC is actively engaged in fear regulation under normal circumstances. In this study, the lateral or medial OFC was inactivated during the extinction phase using the ABA fear renewal procedure. We found that these animals showed intact fear renewal during retrieval test with their freezing levels equivalent to the control rats, revealing that the OFC did not have decisive roles in extinction acquisition. Together with our previous study, we suggest that the OFC only interferes with fear regulation when it becomes pathophysiologically hyperactive.

Effect of stress on spatial working memory and EEG signal dynamics in the follicular and luteal phases of the menstrual cycle in young single girls

AIM

Women undergo behavioral changes during the menstrual cycle. This study aimed to investigate the effect of estradiol (Es) on stress and effect of stress on spatial working memory (WM) and also to investigate electroencephalogram (EEG) signal's dynamics in the early and late follicular (EF and LF) and luteal (LU) phases of unmarried girls' menstrual cycle.

METHODS

Stress was induced by presentation of a short (3 min) movie clip. Simultaneous with a memory test and stress induction, EEG, serum Es levels, and galvanic skin response (GSR) were assessed.

RESULTS

Serum Es concentrations were decreased in LF, LU, and EF phases. The mean GSR score decreased after stress induction in all three phases, but it increased in the LF and LU phases versus the EF phase. Spatial WM diminished after stress induction in all three phases, but it increased in the LF phase versus the two phases before and after stress induction. Average power spectrum density in all frequency bands increased after stress induction in the frontal and prefrontal channels in the spatial WM test.

CONCLUSION

The results showed that stress led to spatial WM dysfunction; however, Es improved spatial WM performance in the LF phase versus the other two phases.

Somatostatin-Expressing Neurons in the Ventral Tegmental Area Innervate Specific Forebrain Regions and Are Involved in Stress Response

Expanding knowledge about the cellular composition of subcortical brain regions demonstrates large heterogeneity and differences from the cortical architecture. Previously we described three subtypes of somatostatin-expressing (Sst) neurons in the mouse ventral tegmental area (VTA) and showed their local inhibitory action on the neighboring dopaminergic neurons (Nagaeva et al., 2020). Here, we report that Sst+ neurons especially from the anterolateral part of the mouse VTA also project far outside the VTA and innervate forebrain regions that are mainly involved in the regulation of emotional behavior, including the ventral pallidum, lateral hypothalamus, the medial part of the central amygdala, anterolateral division of the bed nucleus of stria terminalis, and paraventricular thalamic nucleus. Deletion of these VTASst neurons in mice affected several behaviors, such as home cage activity, sensitization of locomotor activity to morphine, fear conditioning responses, and reactions to the inescapable stress of forced swimming, often in a sex-dependent manner. Together, these data demonstrate that VTASst neurons have selective projection targets distinct from the main targets of VTA dopamine neurons. VTASst neurons are involved in the regulation of behaviors primarily associated with the stress response, making them a relevant addition to the efferent VTA pathways and stress-related neuronal network.

Sex Differences and Similarities in Relations Between Mathematics Achievement, Attitudes, and Anxiety: A Seventh-to-Ninth Grade Longitudinal Study

There are consistent correlations between mathematics achievement, attitudes, and anxiety, but the longitudinal relations among these constructs are not well understood nor are sex differences in these relations. To address this gap, mathematics achievement, attitudes, and anxiety were longitudinally assessed for 342 (169 boys) adolescents from 7th to 9th grade, inclusive, and Latent Growth Curve Models were used to assess the relations among these traits and developmental change in them. Spatial abilities (7th, 8th grade) and trait anxiety (8th, 9th grade) were also assessed and used for control for sex differences in these traits. Overall, boys had stronger spatial abilities and more positive mathematics attitudes and were less anxious than girls, but there were no sex differences in mathematics achievement. Across grades, mathematics achievement improved, attitudes became less positive, and anxiety increased for both boys and girls. Higher than average cross-grade growth in mathematics achievement mitigated boys' developmental declines in mathematics attitudes and increases in anxiety. Girls with strong spatial abilities had lower mathematics anxiety, but girls overall maintained higher mathematics anxiety and less positive mathematics attitudes relative to boys, even when they showed strong cross-grade gains in mathematics achievement. The study demonstrated that longitudinal gains in mathematics are associated with cross-grade changes in attitudes and anxiety but with several different developmental patterns for boys and girls.

Circuit and Cell-Specific Contributions to Decision Making Involving Risk of Explicit Punishment in Male and Female Rats

Decision making is a complex cognitive process that recruits a distributed network of brain regions, including the basolateral amygdala (BLA) and nucleus accumbens shell (NAcSh). Recent work suggests that communication between these structures, as well as activity of cells expressing dopamine (DA) D2 receptors (D2R) in the NAcSh, are necessary for some forms of decision making; however, the contributions of this circuit and cell population during decision making under risk of punishment are unknown. The current experiments addressed this question using circuit-specific and cell type-specific optogenetic approaches in rats during a decision making task involving risk of punishment. In experiment 1, Long-Evans rats received intra-BLA injections of halorhodopsin or mCherry (control) and in experiment 2, D2-Cre transgenic rats received intra-NAcSh injections of Cre-dependent halorhodopsin or mCherry. Optic fibers were implanted in the NAcSh in both experiments. Following training in the decision making task, BLA→NAcSh or D2R-expressing neurons were optogenetically inhibited during different phases of the decision process. Inhibition of the BLA→NAcSh during deliberation (the time between trial initiation and choice) increased preference for the large, risky reward (increased risk taking). Similarly, inhibition during delivery of the large, punished reward increased risk taking, but only in males. Inhibition of D2R-expressing neurons in the NAcSh during deliberation increased risk taking. In contrast, inhibition of these neurons during delivery of the small, safe reward decreased risk taking. These findings extend our knowledge of the neural dynamics of risk taking, revealing sex-dependent circuit recruitment and dissociable activity of selective cell populations during decision making.SIGNIFICANCE STATEMENT Until recently, the ability to dissect the neural substrates of decision making involving risk of punishment (risk taking) in a circuit-specific and cell-specific manner has been limited by the tools available for use in rats. Here, we leveraged the temporal precision of optogenetics, together with transgenic rats, to probe contributions of a specific circuit and cell population to different phases of risk-based decision making. Our findings reveal basolateral amygdala (BLA)→nucleus accumbens shell (NAcSh) is involved in evaluation of punished rewards in a sex-dependent manner. Further, NAcSh D2 receptor (D2R)-expressing neurons make unique contributions to risk taking that vary across the decision making process. These findings advance our understanding of the neural principles of decision making and provide insight into how risk taking may become compromised in neuropsychiatric diseases.

Differential effects of the stress peptides PACAP and CRF on sleep architecture in mice

Stress produces profound effects on behavior, including persistent alterations in sleep patterns. Here we examined the effects of two prototypical stress peptides, pituitary adenylate cyclase-activating polypeptide (PACAP) and corticotropin-releasing factor (CRF), on sleep architecture and other translationally-relevant endpoints. Male and female mice were implanted with subcutaneous transmitters enabling continuous measurement of electroencephalography (EEG) and electromyography (EMG), as well as body temperature and locomotor activity, without tethering that restricts free movement, body posture, or head orientation during sleep. At baseline, females spent more time awake (AW) and less time in slow wave sleep (SWS) than males. Mice then received intracerebral infusions of PACAP or CRF at doses producing equivalent increases in anxiety-like behavior. The effects of PACAP on sleep architecture were similar in both sexes and resembled those reported in male mice after chronic stress exposure. Compared to vehicle infusions, PACAP infusions decreased time in AW, increased time in SWS, and increased rapid eye movement sleep (REM) time and bouts on the day following treatment. In addition, PACAP effects on REM time remained detectable a week after treatment. PACAP infusions also reduced body temperature and locomotor activity. Under the same experimental conditions, CRF infusions had minimal effects on sleep architecture in either sex, causing only transient increases in SWS during the dark phase, with no effects on temperature or activity. These findings suggest that PACAP and CRF have fundamentally different effects on sleep-related metrics, and provide new insights into the mechanisms by which stress disrupts sleep.

Oscillatory and non-oscillatory brain activity reflects fear expression in an immediate and delayed fear extinction task

Fear extinction is pivotal for inhibiting fear responding to former threat-predictive stimuli. In rodents, short intervals between fear acquisition and extinction impair extinction recall compared to long intervals. This is called Immediate Extinction Deficit (IED). Importantly, human studies of the IED are sparse and its neurophysiological correlates have not been examined in humans. We, therefore, investigated the IED by recording electroencephalography (EEG), skin conductance responses (SCRs), an electrocardiogram (ECG), and subjective ratings of valence and arousal. Forty male participants were randomly assigned to extinction learning either 10 min after fear acquisition (immediate extinction) or 24 h afterward (delayed extinction). Fear and extinction recall were assessed 24 h after extinction learning. We observed evidence for an IED in SCR responses, but not in the ECG, subjective ratings, or in any assessed neurophysiological marker of fear expression. Irrespective of extinction timing (immediate vs. delayed), fear conditioning caused a tilt of the non-oscillatory background spectrum with decreased low-frequency power (<30 Hz) for threat-predictive stimuli. When controlling for this tilt, we observed a suppression of theta and alpha oscillations to threat-predictive stimuli, especially pronounced during fear acquisition. In sum, our data show that delayed extinction might be partially advantageous over immediate extinction in reducing sympathetic arousal (as assessed via SCR) to former threat-predictive stimuli. However, this effect was limited to SCR responses since all other fear measures were not affected by extinction timing. Additionally, we demonstrate that oscillatory and non-oscillatory activity is sensitive to fear conditioning, which has important implications for fear conditioning studies examining neural oscillations.

Infralimbic YTHDF1 is necessary for the beneficial effects of acute mild exercise on auditory fear extinction retention

Exposure therapy is the most effective approach of behavioral therapy for anxiety and post-traumatic stress disorder (PTSD). But fear is easy to reappear even after successful extinction. So, identifying novel strategies for augmenting exposure therapy is rather important. It was reported that exercise had beneficial effects on cognitive and memory deficits. However, whether exercise could affect fear memory, especially for fear extinction remained elusive. Here, our results showed that exposure to acute mild exercise 1 or 2 h before extinction training can augment recent fear extinction retention and 2 h for the remote fear extinction retention. These beneficial effects could be attributed to increased YTHDF1 expression in medial prefrontal cortex (mPFC). Furthermore, by using an AAV-shRNA-based approach to silence YTHDF1 expression via stereotactic injection in prelimbic cortex (PL) or infralimbic cortex (IL), respectively, we demonstrated that silence YTHDF1 in IL, but not in PL, blunted augmentation of exposure therapy induced by acute mild exercise and accompanied with decreased NR2B and GluR1 expression. Moreover, YTHDF1 modulated dendritic spines remodeling of pyramidal neuron in IL. Collectively, our findings suggested that acute mild exercise acted as an effective strategy in augmenting exposure therapy with possible implications for understanding new treatment underlying PTSD.

Sex Differences in Behavior and Learning Abilities in Adult Rats

Laboratory rats have excellent learning abilities and are often used in cognitive neuroscience research. The majority of rat studies are conducted on males, whereas females are usually overlooked. Here, we examined sex differences in behavior and tactile sensitivity in littermates during adulthood (5.8-7.6 months of age). We used a battery of behavioral tests, including the 2% sucrose preference test (positive motivation), a free-choice paradigm (T-maze, neutral situation), and associative fear-avoidance learning (negative motivation, aversive situation). Tactile perception was examined using the von Frey test (aversive situation). In two aversive situations (von Frey test and avoidance learning), females were examined during the diestrus stage of the estrous cycle, and ultrasonic vocalization was recorded in both sexes. It was found that (1) females, but not males, lost their body weight on the first day of the sucrose preference test, suggesting sex differences in their reaction to environmental novelty or in metabolic homeostasis; (2) the tactile threshold in females was lower than in males, and females less frequently emitted aversive ultrasonic calls; (3) in the avoidance learning task, around 26% of males (but no females) were not able to learn and experienced frizzing. Overall, the performance of associative fear-avoidance in males was worse than in females. In general, females demonstrated higher abilities of associative learning and less persistently emitted aversive ultrasonic calls.

Circuit and cell-specific contributions to decision making involving risk of explicit punishment in male and female rats

Decision making is a complex cognitive process that recruits a distributed network of brain regions, including the basolateral amygdala (BLA) and nucleus accumbens shell (NAcSh). Recent work suggests that communication between these structures, as well as activity of cells expressing dopamine D2 receptors (D2R) in the NAcSh, are necessary for some forms of decision making; however, the contributions of this circuit and cell population during decision making under risk of punishment are unknown. The current experiments addressed this question using circuit- and cell type-specific optogenetic approaches in rats during a decision-making task involving risk of punishment. In Experiment 1, Long-Evans rats received intra-BLA injections of halorhodopsin or mCherry (control) and in Experiment 2, D2-Cre transgenic rats received intra-NAcSh injections of Cre-dependent halorhodopsin or mCherry. Optic fibers were implanted in the NAcSh in both experiments. Following training in the decision-making task, BLA→NAcSh or D2R-expressing neurons were optogenetically inhibited during different phases of the decision process. Inhibition of the BLA→NAcSh during deliberation (the time between trial initiation and choice) increased choice of the large, risky reward (increased risk taking). Similarly, inhibition during delivery of the large, punished reward increased risk taking, but only in males. Inhibition of D2R-expressing neurons in the NAcSh during deliberation increased risk taking. In contrast, inhibition of these neurons during delivery of the small, safe reward decreased risk taking. These findings extend our knowledge of the neural dynamics of risk taking, revealing sex-dependent circuit recruitment and dissociable activity of selective cell populations during decision making.

Recent advances in dopamine D2 receptor ligands in the treatment of neuropsychiatric disorders

Dopamine is a biologically active amine synthesized in the central and peripheral nervous system. This biogenic monoamine acts by activating five types of dopamine receptors (D_1-5 Rs), which belong to the G protein-coupled receptor family. Antagonists and partial agonists of D₂ Rs are used to treat schizophrenia, Parkinson's disease, depression, and anxiety. The typical pharmacophore with high D₂ R affinity comprises four main areas, namely aromatic moiety, cyclic amine, central linker and aromatic/heteroaromatic lipophilic fragment. From the literature reviewed herein, we can conclude that 4-(2,3-dichlorophenyl), 4-(2-methoxyphenyl)-, 4-(benzo[b]thiophen-4-yl)-1-substituted piperazine, and 4-(6-fluorobenzo[d]isoxazol-3-yl)piperidine moieties are critical for high D₂ R affinity. Four to six atoms chains are optimal for D₂ R affinity with 4-butoxyl as the most pronounced one. The bicyclic aromatic/heteroaromatic systems are most frequently occurring as lipophilic appendages to retain high D₂ R affinity. In this review, we provide a thorough overview of the therapeutic potential of D₂ R modulators in the treatment of the aforementioned disorders. In addition, this review summarizes current knowledge about these diseases, with a focus on the dopaminergic pathway underlying these pathologies. Major attention is paid to the structure, function, and pharmacology of novel D₂ R ligands, which have been developed in the last decade (2010-2021), and belong to the 1,4-disubstituted aromatic cyclic amine group. Due to the abundance of data, allosteric D₂ R ligands and D₂ R modulators from patents are not discussed in this review.

The Impacts of Sex Differences and Sex Hormones on Fear Extinction

Fear extinction memories are strongly modulated by sex and hormonal status, but the exact mechanisms are still being discovered. In humans, there are some basal and task-related features in which male and female individuals differ in fear conditioning paradigms. However, analyses considering the effects of sex hormones demonstrate a role for estradiol in fear extinction memory consolidation. Translational studies are taking advantage of the convergent findings between species to understand the brain structures implicated. Nevertheless, the human brain is complex and the transfer of these findings into the clinics remains a challenge. The promising advances in the field together with the standardization of fear extinction methodologies in humans will benefit the design of new personalized therapies.

Effect of developmental stress on the in vivo neuronal circuits related to excitation-inhibition balance and mood in adulthood

INTRODUCTION

Traumatic events in early life have a deleterious effect on the development of normal brain developments, which may be a cause of various psychiatric disorders in adulthood. Most prior studies focused on molecular biological aspects, and research on functional changes in neural circuits is still limited. We aimed to elucidate the effect of early life stress on in vivo excitation-inhibition and serotonergic neurotransmission in the adulthood using non-invasive functional molecular imaging (positron emission tomography, PET).

METHODS

To compare the effect of stress intensity, early life stress animal models were divided into single trauma (MS) and double trauma groups (MRS). MS was derived from maternal separation, whereas MRS was derived from maternal separation and restraint stress after birth. And to evaluate the stress vulnerability on the sex, we used male and female rats.

RESULTS

The MRS group showed greater weight loss and more severe depressive/anxiety-like behaviors than the MS and control groups. Corticosterone levels in MRS showed a greater extent of decline than in the MS group; however, there was no significant difference in the change of T3 and T4 between MS and MRS. In the PET, the stress exposure groups showed lower brain uptake for GABAergic, glutamatergic, and serotonergic systems compared with the control group. The excitatory/inhibitory balance, which was derived by dividing glutamate brain uptake into GABAergic uptake, increased as stress intensity increased. Neuronal degeneration in the stress exposure groups was confirmed by immunohistochemistry. In the sex comparison, female showed the greater changes of body weight, corticosterone level, depressive/anxiety-like behavior, and neurotransmission systems than those in male.

CONCLUSION

Taken together, we demonstrated that developmental stress induces dysfunction of neurotransmission in vivo, and that females are more vulnerable to stress than males.

How Different Factors in Combination Change Fear Extinction Learning: The Case of Sex and Stress Hormones

Effects of a specific factor on fear extinction or exposure therapy have revealed promising results, for example how sex or stress hormones exert the capability to critically change extinction learning and consolidation processes. However, we must acknowledge that in real life these factors do not operate in isolation, they go hand in hand. In this chapter, the available evidence regarding interactions of sex and stress hormones on extinction processes and exposure therapy will be integrated and discussed. First hints exist that these factors in combination critically target extinction learning and consolidation processes, calling for more detailed research on the exact underlying mechanisms. In addition to experiments with high sample sizes, we must aim for a collaborative effort of laboratories across the whole world to be able to identify critical combinations of factors associated with improved, but also impaired extinction processes and exposure therapy success. We expect that the revelation of further relevant factors will not only be limited to the interplay between sex and stress hormones but will include factors such as sleep and exercise as well. In the long run, uncovering the most important interaction effects will give us critical hints for differential treatment options to be realized in the sense of a personalized medicine approach.

Exogenous estradiol and oxytocin modulate sex differences in hippocampal reactivity during the encoding of episodic memories

Considerable evidence supports sex differences in episodic memory. The hormones estradiol and oxytocin both affect episodic memory and may contribute to these sex differences, but possible underlying hormonal interactions have not been tested in a sample involving both sexes. To this end, we conducted a randomized, placebo-controlled, parallel-group functional magnetic resonance imaging (fMRI) study including healthy free-cycling women (n = 111) and men (n = 115). The fMRI session was conducted under four experimental conditions: 1. transdermal estradiol (2 mg) and intranasal oxytocin (24 IU), 2. transdermal placebo and intranasal oxytocin, 3. transdermal estradiol and intranasal placebo, 4. transdermal placebo and intranasal placebo. Participants were scanned during the encoding of positive, neutral, and negative scenes. Recognition memory was tested three days following the scanning sessions without additional treatments. Under placebo, women showed a significantly better recognition memory and increased hippocampal responses to subsequently remembered items independent of the emotional valence compared to men. The separate treatments with either hormone significantly diminished this mnemonic sex difference and reversed the hippocampal activation pattern. However, the combined treatments produced no significant effect. Collectively, the results suggest that both hormones play a crucial role in modulating sex differences in episodic memory. Furthermore, possible antagonistic interactions between estradiol and oxytocin could explain previously observed opposing hormonal effects in women and men.

Alterations of mitochondrial dynamics in serotonin transporter knockout rats: A possible role in the fear extinction recall mechanisms

Stress-related mental disorders encompass a plethora of pathologies that share the exposure to a negative environment as trigger for their development. The vulnerability to the effects of a negative environment is not equal to all but differs between individuals based on the genetic background makeup. Here, to study the molecular mechanisms potentially underlying increased threat anticipation, we employed an animal model showing this symptom (5-HTT knockout rats) which we exposed to Pavlovian fear conditioning (FC). We investigated the role of mitochondria, taking advantage of the recent evidence showing that the dynamic of these organelles is dysregulated after stress exposure. Behavioral experiments revealed that, during the second day of extinction of the FC paradigm, 5-HTT knockout (5-HTT-/-) animals showed a lack of fear extinction recall. From a mechanistic standpoint, we carried out our molecular analyses on the amygdala and prefrontal cortex, given their role in the management of the fear response due to their tight connection. We demonstrated that mitochondrial dynamics are impaired in the amygdala and prefrontal cortex of 5-HTT-/- rats. The dissection of the potential contributing factors revealed a critical role in the mechanisms regulating fission and fusion that are dysregulated in transgenic animals. Furthermore, mitochondrial oxidative phosphorylation, mitochondrial biogenesis, and the production of antioxidant enzymes were altered in these brain regions in 5-HTT-/- rats. In summary, our data suggest that increased extracellular 5-HT levels cause an unbalance of mitochondrial functionality that could contribute to the reduced extinction recall of 5-HTT-/- rats, pointing out the role of mitochondrial dynamics in the etiology of psychiatric disorders. Our findings, also, provide some interesting insights into the targeted development of drugs to treat such disorders.

Hormonal contraceptive usage influences stress hormone effects on cognition and emotion

Men and women partially differ in how they respond to stress and how stress in return affects their cognition and emotion. The influence of hormonal contraceptives (HCs) on this interaction has received little attention, which is surprising given the prevalence of HC usage. This selective review illustrates how HC usage modulates the effects of stress hormones on cognition and emotion. As three examples, we discuss stress hormone effects on episodic memory, fear conditioning and cognitive emotion regulation. The identified studies revealed that stress effects on cognitive-emotional processes in women using HCs were at times reduced or even absent when compared to men or naturally cycling women. Especially striking were the few examples of reversed effects in HC women. As underlying neuroendocrine mechanisms, we discuss influences of HCs on the neuroendocrine stress response and effects of HCs on central glucocorticoid sensitivity. The summarized findings emphasize the need for additional translational research.

Aberrant orbitofrontal cortical activation interferes with encoding of Pavlovian fear conditioning

Obsessive-compulsive disorder (OCD) patients were usually found with the hyper-activation of the orbitofrontal cortex (OFC) and a deficit in fear extinction learning. The OFC can be subdivided into the lateral OFC (lOFC) and the medial OFC (mOFC). Previous studies have suggested that both subregions are involved in the modulation of negative emotions. However, how aberrant activation of the OFC interacts with the encoding of Pavlovian fear remains unknown. In this study, the lOFC or the mOFC was pharmacologically activated or inactivated before the fear conditioning on Day 1, followed by a context test on Day 2 and a tone test on Day 3 in male Long-Evans rats. We found that for the animals that underwent fear conditioning under aberrant activation of either the lOFC or the mOFC, they showed normal within-session fear expression. However, the acquisition/consolidation of contextual fear was impaired under mOFC activation, while the acquisition/consolidation of cued fear was impaired under either the lOFC or the mOFC activation, in that these animals showed lower freezing compared to controls during the retrieval test. On the other hand, for the animals that underwent fear conditioning under inactivation of either the lOFC or the mOFC, they showed normal within-session fear expression, as well as intact encoding of both the contextual and cued fear. Together, our results suggested that the OFC was not actively engaged in the acquisition of Pavlovian fear conditioning, but aberrant activation of the OFC impaired fear learning.

Regulation of sex differences in risk-based decision making by gonadal hormones: Insights from rodent models

Men and women differ in their ability to evaluate options that vary in their rewards and the risks that are associated with these outcomes. Most studies have shown that women are more risk averse than men and that gonadal hormones significantly contribute to this sex difference. Gonadal hormones can influence risk-based decision making (i.e., risk taking) by modulating the neurobiological substrates underlying this cognitive process. Indeed, estradiol, progesterone and testosterone modulate activity in the prefrontal cortex, amygdala and nucleus accumbens associated with reward and risk-related information. The use of animal models of decision making has advanced our understanding of the intersection between the behavioral, neural and hormonal mechanisms underlying sex differences in risk taking. This review will outline the current state of this literature, identify the current gaps in knowledge and suggest the neurobiological mechanisms by which hormones regulate risky decision making. Collectively, this knowledge can be used to understand the potential consequences of significant hormonal changes, whether endogenously or exogenously induced, on risk-based decision making as well as the neuroendocrinological basis of neuropsychiatric diseases that are characterized by impaired risk taking, such as substance use disorder and schizophrenia.

PACAP-PAC1R modulates fear extinction via the ventromedial hypothalamus

Exposure to traumatic stress can lead to fear dysregulation, which has been associated with posttraumatic stress disorder (PTSD). Previous work showed that a polymorphism in the PACAP-PAC1R (pituitary adenylate cyclase-activating polypeptide) system is associated with PTSD risk in women, and PACAP (ADCYAP1)-PAC1R (ADCYAP1R1) are highly expressed in the hypothalamus. Here, we show that female mice subjected to acute stress immobilization (IMO) have fear extinction impairments related to Adcyap1 and Adcyap1r1 mRNA upregulation in the hypothalamus, PACAP-c-Fos downregulation in the Medial Amygdala (MeA), and PACAP-FosB/ΔFosB upregulation in the Ventromedial Hypothalamus dorsomedial part (VMHdm). DREADD-mediated inhibition of MeA neurons projecting to the VMHdm during IMO rescues both PACAP upregulation in VMHdm and the fear extinction impairment. We also found that women with the risk genotype of ADCYAP1R1 rs2267735 polymorphism have impaired fear extinction.

Sex hormones and physical function among the Chinese oldest-old and centenarian women

Background

Physical independence is crucial for overall health in the elderly individuals. The life expectancy of women has been shown to be higher than that of men, which is also known as the “male–female health-survival paradox”. Sex hormones may be one of the explanations. However, the relationships between sex hormones and physical function remain unclear in the elderly females. This study was designed to explore these relationships among the Chinese oldest-old and centenarian women.

Methods

Data from 1226 women were obtained from the China Hainan Centenarian Cohort Study. Home interviews, physical examinations and blood analyses were conducted using standardized procedures. Variables including age, Han ethnicity, illiteracy, smoker, drinker, estradiol (E2), testosterone (T), follicle-stimulating hormone, and luteinizing hormone were used in the multivariate logistic and linear regression analyses.

Results

In all the participants, age [beta (95% confidence interval): − 0.84 (− 0.98, − 0.71)] and E2 levels [beta (95% confidence interval): − 0.22 (− 0.28, − 0.17)] were negatively associated with activities of daily living (ADLs) in the multivariate linear regression analyses (P < 0.05 for all). We also observed significantly negative associations of age [odds ratio (95% confidence interval): 0.90 (0.88, 0.91)] and E2 levels [odds ratio (95% confidence interval): 0.98 (0.98, 0.99)] with physical normality in the multivariate logistic regression analyses (P < 0.05 for all). Age and E2 levels gradually decreased with increases in the ADL quartiles across all the participants (P < 0.05 for all).

Conclusions

This study demonstrated that E2 levels were negatively associated with physical function among the Chinese oldest-old and centenarian women.

Role of noradrenergic arousal for fear extinction processes in rodents and humans

Fear extinction is a learning mechanism that is pivotal for the inhibition of fear responses towards cues or contexts that no longer predict the occurrence of a threat. Failure of fear extinction leads to fear expression under safe conditions and is regarded to be a cardinal characteristic of many anxiety-related disorders and posttraumatic stress disorder. Importantly, the neurotransmitter noradrenaline was shown to be a potent modulator of fear extinction. Rodent studies demonstrated that excessive noradrenaline transmission after acute stress opens a time window of vulnerability, in which fear extinction learning results in attenuated long-term extinction success. In contrast, when excessive noradrenergic transmission subsides, well-coordinated noradrenaline transmission is necessary for the formation of a long-lasting extinction memory. In addition, emerging evidence suggests that the neuropeptide corticotropin releasing hormone (CRF), which strongly regulates noradrenaline transmission under conditions of acute stress, also impedes long-term extinction success. Recent rodent work - using sophisticated methods - provides evidence for a hypothetical mechanistic framework of how noradrenaline and CRF dynamically orchestrate the neural fear and extinction circuitry to attenuate or to improve fear extinction and extinction recall. Accordingly, we review the evidence from rodent studies linking noradrenaline and CRF to fear extinction learning and recall and derive the hypothetical mechanistic framework of how different levels of noradrenaline and CRF may create a time window of vulnerability which impedes successful long-term fear extinction. We also address evidence from human studies linking noradrenaline and fear extinction success. Moreover, we accumulate emerging approaches to non-invasively measure and manipulate the noradrenergic system in healthy humans. Finally, we emphasize the importance of future studies to account for sex (hormone) differences when examining the interaction between fear extinction, noradrenaline, and CRF. To conclude, NA's effects on fear extinction recall strongly depend on the arousal levels at the onset of fear extinction learning. Our review aimed at compiling the available (mainly rodent) data in a neurobiological framework, suited to derive testable hypotheses for future work in humans.

Alcohol Dependence Induces CRF Sensitivity in Female Central Amygdala GABA Synapses

Alcohol use disorder (AUD) is a chronically relapsing disease characterized by loss of control in seeking and consuming alcohol (ethanol) driven by the recruitment of brain stress systems. However, AUD differs among the sexes: men are more likely to develop AUD, but women progress from casual to binge drinking and heavy alcohol use more quickly. The central amygdala (CeA) is a hub of stress and anxiety, with corticotropin-releasing factor (CRF)-CRF1 receptor and Gamma-Aminobutyric Acid (GABA)-ergic signaling dysregulation occurring in alcohol-dependent male rodents. However, we recently showed that GABAergic synapses in female rats are less sensitive to the acute effects of ethanol. Here, we used patch-clamp electrophysiology to examine the effects of alcohol dependence on the CRF modulation of rat CeA GABAergic transmission of both sexes. We found that GABAergic synapses of naïve female rats were unresponsive to CRF application compared to males, although alcohol dependence induced a similar CRF responsivity in both sexes. In situ hybridization revealed that females had fewer CeA neurons containing mRNA for the CRF1 receptor (Crhr1) than males, but in dependence, the percentage of Crhr1-expressing neurons in females increased, unlike in males. Overall, our data provide evidence for sexually dimorphic CeA CRF system effects on GABAergic synapses in dependence.

Association between traffic-related air pollution and anxiety hospitalizations in a coastal Chinese city: are there potentially susceptible groups?

Motor vehicle exhaust emissions have become the main source of urban air pollution in China, but few studies have explored the association of short-term exposure to traffic-related air pollutants (TRAPs) with anxiety disorders. Thus, we used an overdispersed, generalized additive model (GAM) to investigate the association between TRAPs and hospital admissions (HAs) for anxiety in Qingdao, a coastal Chinese city with high vehicle ownership. In addition, stratified analyses were performed by gender, age, season and hospitalization frequency (first admission and readmission). A positive association between TRAPs and HAs for anxiety was observed. Both inhalable particulate matter (PM₁₀) and nitrogen dioxide (NO₂) showed significant effects at lag 3 in the single-day lag structure, and each 10 μg/m³ increase in the concentrations was significantly associated with increases of 0.88% [95% confidence interval (CI): 0.04%, 1.72%] for PM₁₀ and 2.74% (0.45%, 5.08%) for NO₂ on anxiety hospitalizations. For fine particulate matter (PM_2.5) and carbon monoxide (CO), the strongest effects were found at lag05 and lag04 [2.67% (0.77%, 4.62%) and 0.19% (0.04%, 0.34%), respectively] in the multiday lag structure. The estimates of PM_2.5 were relatively robust after adjusting for other pollutants in the two-pollutant model. Stratified analyses indicated that the associations were stronger in females and younger individuals (<45 in age) than in males and elderly individuals (≥45 in age). Furthermore, the effects of PM_2.5 and CO were most obvious during the cold season. Regarding hospitalization frequency, only PM_2.5 was found to have a significant effect in the first-admission group. The results showed that short-term exposure to TRAPs, especially to PM_2.5, was significantly associated with the increased risk of daily HAs for anxiety, which can help clinicians and policymakers better understand the effects of TRAPs to implement targeted interventions.

Distinct and Convergent Beneficial Effects of Estrogen and Insulin on Cognitive Function in Healthy Young Men

CONTEXT

Systematic investigations into the cognitive impact of estradiol and insulin in male individuals are sparse, and it is unclear whether the 2 hormones interact to benefit specific cognitive functions in humans.

OBJECTIVE

We investigated the acute effect of estradiol and insulin and of their combined administration on divergent (creative) and convergent (arithmetical) thinking as well as short-term and working verbal memory in healthy young men.

METHODS

According to a 2 × 2 design, 2 groups of men (each n = 16) received a 3-day transdermal estradiol (100 µg/24 h) or placebo pretreatment and on 2 separate mornings were intranasally administered 160 IU regular human insulin and, respectively, placebo before completing a battery of cognitive tests; we also determined relevant blood parameters.

RESULTS

Estrogen compared with placebo treatment induced a 3.5-fold increase in serum estradiol and suppressed serum testosterone concentrations by 70%. Estrogen in comparison to placebo improved creative performance, that is, verbal fluency and flexibility, but not arithmetical thinking, as well as verbal short-term memory, but not visuospatial memory. The combination of estrogen and insulin enhanced recognition discriminability at delayed verbal memory recall; insulin alone remained without effect.

CONCLUSION

Estrogen specifically enhances core aspects of creativity and verbal memory in young male individuals; delayed recognition memory benefits from the combined administration of estradiol and insulin. Our results indicate that insulin's acute cognitive impact in young men is limited and not robustly potentiated by estradiol. Estradiol per se exerts a beneficial acute effect on creative and verbal performance in healthy young men.

Sex hormones and cortisol during experimental trauma memory consolidation: Prospective association with intrusive memories

Background Trauma- and stress-related disorders, such as post-traumatic stress disorder (PTSD), are more common in females than in males. Sex hormones affect learning and emotional memory formation and may be associated with the development of PTSD. Most previous studies have indexed these hormones in isolation. Objectives: To investigate associations of sex hormones and cortisol during memory consolidation on the development of intrusive memories. Methods: We employed an experimental trauma film paradigm in 61 healthy women and indexed salivary testosterone, progesterone, estradiol, and cortisol on day one and day two post experimental trauma exposure and their effects on intrusion frequency, distress, and vividness. Intrusive trauma memories were indexed by means of a diary in which participants documented intrusion frequency, distress, and vividness. Results and conclusion: Participants reported an average of 5.3 intrusions over the course of seven days (SD = 4.6, range 0-26). Progesterone, and estradiol indexed on day one predicted intrusion frequency, with higher progesterone and lower estradiol predicting more intrusive memories (p-values AUC progesterone 0.01 and estradiol 0.02). There was no evidence for associations between hormone concentration indices on day two and intrusion outcomes. Further research on the roles of gonadal and adrenal hormones in trauma memory formation is needed to advance our efforts to understand their influence on PTSD development.

[Research for sex differences in fear extinction]

Fear memory has an important role in survival, but excess fear memory could be cause to fear-related disorders such as post traumatic disorder (PTSD). People who undergo a fearful event do not always develop PTSD, suggesting that there are vulnerable factors to develop the disorder. It is believed that sex, in particular female, is one of the factors as it is known that the prevalence rate of PTSD is higher in women than in men. However, the biological mechanisms underlying the sex differences in their prevalence rate remain unclear. Because previous studies reported that patients with fear-related disorders show an impairment of fear extinction, investigation of sex differences in fear extinction may be useful for understanding the greater vulnerability of women to fear-related disorders. Although number of papers investigating sex differences in fear extinction, these reports have increased recently. This review introduces fear extinction, sex differences in fear extinction is low, and the molecular mechanisms of sex differences in fear extinction. In the molecular mechanisms, we focused brain-derived neurotrophic factor (BDNF)-tropomyosin-related kinase B (TrkB) receptor signal which has been investigated by independent research groups.

Psychobiological risk factors for suicidal thoughts and behaviors in adolescence: a consideration of the role of puberty

Suicide is the second leading cause of death among adolescents. While clinicians and researchers have begun to recognize the importance of considering multidimensional factors in understanding risk for suicidal thoughts and behaviors (STBs) during this developmental period, the role of puberty has been largely ignored. In this review, we contend that the hormonal events that occur during puberty have significant effects on the organization and development of brain systems implicated in the regulation of social stressors, including amygdala, hippocampus, striatum, medial prefrontal cortex, orbitofrontal cortex, and anterior cingulate cortex. Guided by previous experimental work in adults, we also propose that the influence of pubertal hormones and social stressors on neural systems related to risk for STBs is especially critical to consider in adolescents with a neurobiological sensitivity to hormonal changes. Furthermore, facets of the pubertal transition, such as pubertal timing, warrant deeper investigation and may help us gain a more comprehensive understanding of sex differences in the neurobiological and psychosocial mechanisms underlying adolescent STBs. Ultimately, advancing our understanding of the pubertal processes that contribute to suicide risk will improve early detection and facilitate the development of more effective, sex-specific, psychiatric interventions for adolescents.

Attractin Participates in Schizophrenia by Affecting Testosterone Levels

Attractin (ATRN) is a widely expressed glycoprotein that is involved in energy homeostasis, neurodevelopment, and immune response. It is encoded by a gene spanning 180 kb on chromosome 20p13, a region previously implicated in schizophrenia by linkage studies. To address a possible role of ATRN in disorders of the central nervous system, we created an atrn knockout zebrafish line and performed behavioral tests. Adult atrn^–/– zebrafish exhibited more pronounced attack behavior relative to wild-type control zebrafish in a tracking analysis. Biochemical analysis revealed elevated testosterone levels in atrn^–/– zebrafish. At the gene expression level, we noted an upregulation of cyp51 and hsd17b7, key proteins in testosterone synthesis in the brains of both adult and larvae of atrn^–/– zebrafish. In order to further elucidate the relationship between testosterone and behavioral syndromes, we then compared testosterone levels of 9,008 psychiatric patients and 247 healthy controls from the same catchment area. Of all subjects examined, male subjects with schizophrenia exhibited lower testosterone levels compared with controls. In contrast, female subjects with a diagnosis of schizophrenia or bipolar disorder featured higher testosterone levels than did same sex controls. Purposeful sampling of extreme groups showed reduced ATRN expression in a subset of these subjects. Finally, we identified 14 subjects with ATRN mutations. All of whom displayed abnormal testosterone levels. In summary, the interplay of ATRN and testosterone may help to explain sexual dimorphisms in selected behavioral phenotypes.

Sex and context differences in the effects of trauma on comorbid alcohol use and post-traumatic stress phenotypes in actively drinking rats

Alcohol use disorder (AUD) and affective disorders are frequently comorbid and share underlying mechanisms that could be targets for comprehensive treatment. Post-traumatic stress disorder (PTSD) has high comorbidity with AUD, but comprehensive models of this overlap are nascent. We recently characterized a model of comorbid AUD and PTSD-like symptoms, wherein stressed rats receive an inhibitory avoidance (IA)-related footshock on two occasions followed by two-bottle choice (2BC) voluntary alcohol drinking. Stressed rats received the second footshock in a familiar (FAM, same IA box as the first footshock) or novel context (NOV, single-chambered apparatus); the FAM paradigm more effectively increased alcohol drinking in males and the NOV paradigm in females. During abstinence, stressed males displayed avoidance-like PTSD symptoms, and females showed hyperarousal-like PTSD symptoms. Rats in the model had altered spontaneous action potential-independent GABAergic transmission in the central amygdala (CeA), a brain region key in alcohol dependence and stress-related signaling. However, PTSD sufferers may have alcohol experience prior to their trauma. Here, we therefore modified our AUD/PTSD comorbidity model to provide 3 weeks of intermittent extended alcohol access before footshock and then studied the effects of NOV and FAM stress on drinking and PTSD phenotypes. NOV stress suppressed the escalation of alcohol intake and preference seen in male controls, but no stress effects were seen on drinking in females. Additionally, NOV males had decreased action potential-independent presynaptic GABA release and delayed postsynaptic GABAA receptor kinetics in the CeA compared to control and FAM males. Despite these changes to alcohol intake and CeA GABA signaling, stressed rats showed broadly similar anxiogenic-like behaviors to our previous comorbid model, suggesting decoupling of the PTSD symptoms from the AUD vulnerability for some of these animals. The collective results show the importance of alcohol history and trauma context in vulnerability to comorbid AUD/PTSD-like symptoms.

Impact of exogenous estradiol on task-based and resting-state neural signature during and after fear extinction in healthy women

Fluctuations of endogenous estrogen modulates fear extinction, but the influence of exogenous estradiol is less studied. Moreover, little focus has been placed on the impact of estradiol on broad network connectivity beyond the fear extinction circuit. Here, we examined the effect of acute exogenous estradiol administration on fear extinction-induced brain activation, whole-brain functional connectivity (FC) during the fear extinction task and post-extinction resting-state. Ninety healthy women (57 using oral contraceptives [OC], 33 naturally cycling [NC]) were fear conditioned on day 1. They ingested an estradiol or placebo pill prior to extinction learning on day 2 (double-blind design). Extinction memory was assessed on day 3. Task-based functional MRI data were ascertained on days 2 and 3 and resting-state data were collected post-extinction on day 2 and pre-recall on day 3. Estradiol administration significantly modulated the neural signature associated with fear extinction learning and memory, consistent with prior studies. Importantly, estradiol administration induced significant changes in FC within multiple networks, including the default mode and somatomotor networks during extinction learning, post-extinction, and during extinction memory recall. Exploratory analyses revealed that estradiol impacted ventromedial prefrontal cortex (vmPFC) activation and FC differently in the NC and OC women. The data implicate a more diffused and significant effect of acute estradiol administration on multiple networks. Such an effect might be beneficial to modulating attention and conscious processes in addition to engaging neural processes associated with emotional learning and memory consolidation.

Sex and region-specific effects of variable stress on microglia morphology

Major Depressive Disorder (MDD) is a common and debilitating mood disorder that is more prevalent in women than men. In humans, PET imaging of microglia activation is currently being explored as a potential biomarker of MDD and suicidal ideation. Stress is a trigger for many mood disorders, including MDD. Microglial changes in morphology and activation state in response to stress has been reported in various brain regions, but most studies only examined male subjects. Here we report changes in microglia morphology in the nucleus accumbens (NAc) and subregions of the hippocampus (HPC) in both male and female mice following variable stress of 6 or 28 days in duration. Our data demonstrate that after 6 days of stress, microglia in the female NAc and dentate gyrus have a reduction in homeostatic associated morphology and an increase in primed microglia. After 28 days some of these sex specific stress effects were still present in microglia within the NAc but not the dentate gyrus. There were no effects of stress in either sex at either timepoint in CA1. In female mice, anti-inflammatory activation of microglia using rosiglitazone promoted sociability behavior after 6 days of stress. Furthermore, both drug and stress have impact on microglia morphology and activation state in the NAc. These data suggest that microglia morphology and activation state are altered by 6 days of variable stress in a region-specific manner and may contribute to, or potentially compensate for, the onset of stress susceptibility rather than impacting long term exposure to stress.

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There are region and sex specific effects of stress on microglia.

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Female microglia respond more strongly to shorter periods of stress.

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Rosiglitazone increases social interaction in stressed female mice.

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Rosiglitazone does not block stress induced microglia activation in females.

Estradiol administration modulates neural emotion regulation

Variations of sex hormones during the menstrual cycle can lead to changes in emotion processing. The ability to successfully regulate one's emotions is associated with better social abilities and mental health. While women show better performance in fear extinction learning under high estradiol (E2) compared to women under low E2 levels, little is known about the effect of E2 on emotion regulation. We explored whether E2 modulates emotion regulation in a functional magnetic resonance imaging paradigm and administered E2 valerate to 32 young naturally cycling women during their early follicular phase in a double-blind, placebo-controlled within-subject design. This standardized experimental control allowed us to explore the specific effect of E2 on emotion regulation while controlling for other hormones varying throughout the menstrual cycle. Behaviorally, no difference between conditions appeared. However, on the neural level, E2 administration was associated with lower activation in the right lingual- and left calcarine gyrus, right orbitofrontal cortex and left hippocampus relative to placebo. With respect to the main effect of down-regulation higher activation of the right superior frontal gyrus and left dorsomedial prefrontal cortex was seen; which is in accordance to previous literature. An interaction between drug condition and emotion regulation appeared for the left inferior frontal gyrus extending into the middle frontal gyrus indicating lower activation during down-regulation in the E2 condition than the placebo condition. On the behavioral level, women reported less negative affect in the E2 condition. The results fit well to a previously described psychoneuroendocrinological model in which E2 plays an important modulatory role on emotional processes and risk factors of mental health in women.

Gonadal steroid hormones and emotional memory consolidation: A systematic review and meta-analysis

Anxiety and stress-related disorders are more prevalent in women and associated with negative emotional memory consolidation as well as impaired fear extinction recall. Recent research has identified a role of gonadal steroid hormones in influencing emotional memories and fear extinction, however most individual studies have small samples and employed various protocols. A systematic review and meta-analysis were conducted on studies that examined sex hormones (estrogen, progesterone, testosterone, allopregnanolone, dehydroepiandrosterone) on four aspects of memory, namely, intentional recall (k = 13), recognition memory (k = 7), intrusive memories (k = 9), and extinction recall (k = 11). The meta-analysis on natural cycling women revealed that progesterone level was positively associated with negative recall and negative intrusive memories, and this effect on intentional recall was enhanced under stress induction. Estradiol level was positively associated with extinction recall. This study reveals an important role of progesterone and estradiol in influencing emotional memory consolidation. It highlights the need to control for these hormonal effects and examine progesterone and estradiol concurrently across all menstrual phases in future emotional memory paradigms.

Effect of Estrous Cycle on Behavior of Females in Rodent Tests of Anxiety

Anxiety disorders are more prevalent in women than in men. In women the menstrual cycle introduces another variable; indeed, some conditions e.g., premenstrual syndrome, are menstrual cycle specific. Animal models of fear and anxiety, which form the basis for research into drug treatments, have been developed almost exclusively, using males. There remains a paucity of work using females and the available literature presents a confusing picture. One confound is the estrous cycle in females, which some authors consider, but many do not. Importantly, there are no accepted standardized criteria for defining cycle phase, which is important given the rapidly changing hormonal profile during the 4-day cycle of rodents. Moreover, since many behavioral tests that involve a learning component or that consider extinction of a previously acquired association require several days to complete; the outcome may depend on the phase of the cycle on the days of training as well as on test days. In this article we consider responsiveness of females compared to males in a number of commonly used behavioral tests of anxiety and fear that were developed in male rodents. We conclude that females perform in a qualitatively similar manner to males in most tests although there may be sex and strain differences in sensitivity. Tests based on unconditioned threatening stimuli are significantly influenced by estrous cycle phase with animals displaying increased responsiveness in the late diestrus phase of the cycle (similar to the premenstrual phase in women). Tests that utilize conditioned fear paradigms, which involve a learning component appear to be less impacted by the estrous cycle although sex and cycle-related differences in responding can still be detected. Ethologically-relevant tests appear to have more translational value in females. However, even when sex differences in behavior are not detected, the same outward behavioral response may be mediated by different brain mechanisms. In order to progress basic research in the field of female psychiatry and psychopharmacology, there is a pressing need to validate and standardize experimental protocols for using female animal models of anxiety-related states.

Beyond Efficacy and Effectiveness: Clinical Efficiency Is Necessary for Dissemination

Nearly all patients interact with critical gatekeepers-insurance companies or centralized healthcare systems. For mental health dissemination efforts to be successful, these gatekeepers must refer patients to evidence-based care. To make these referral decisions, they require evidence about the amount of resources expended to achieve therapeutic gains. Without this information, a bottleneck to widespread dissemination of evidence-based care will remain. To address this need for information, we introduce a new perspective, clinical efficiency. This approach directly ties resource usage to clinical outcomes. We highlight how cost-effectiveness approaches and other strategies can address clinical efficiency, and we also introduce a related new metric, the incremental time efficiency ratio (ITER). The ITER is particularly useful for quantifying the benefits of low-intensity and concentrated interventions, as well as stepped-care approaches. Given that stakeholders are increasingly requiring information on resource utilization, the ITER is a metric that can be estimated for past and future clinical trials. As a result, the ITER can allow researchers to better communicate desirable aspects of treatment, and an increased focus on clinical efficiency can improve our ability to deliver high-quality treatment to more patients in need.

Molecular motor protein KIF5C mediates structural plasticity and long-term memory by constraining local translation

Synaptic structural plasticity, key to long-term memory storage, requires translation of localized RNAs delivered by long-distance transport from the neuronal cell body. Mechanisms and regulation of this system remain elusive. Here, we explore the roles of KIF5C and KIF3A, two members of kinesin superfamily of molecular motors (Kifs), and find that loss of function of either kinesin decreases dendritic arborization and spine density whereas gain of function of KIF5C enhances it. KIF5C function is a rate-determining component of local translation and is associated with ∼650 RNAs, including EIF3G, a regulator of translation initiation, and plasticity-associated RNAs. Loss of function of KIF5C in dorsal hippocampal CA1 neurons constrains both spatial and contextual fear memory, whereas gain of function specifically enhances spatial memory and extinction of contextual fear. KIF5C-mediated long-distance transport of local translation substrates proves a key mechanism underlying structural plasticity and memory.

Sex-Specific Effects of Stress on Respiratory Control: Plasticity, Adaptation, and Dysfunction

As our understanding of respiratory control evolves, we appreciate how the basic neurobiological principles of plasticity discovered in other systems shape the development and function of the respiratory control system. While breathing is a robust homeostatic function, there is growing evidence that stress disrupts respiratory control in ways that predispose to disease. Neonatal stress (in the form of maternal separation) affects "classical" respiratory control structures such as the peripheral O₂ sensors (carotid bodies) and the medulla (e.g., nucleus of the solitary tract). Furthermore, early life stress disrupts the paraventricular nucleus of the hypothalamus (PVH), a structure that has emerged as a primary determinant of the intensity of the ventilatory response to hypoxia. Although underestimated, the PVH's influence on respiratory function is a logical extension of the hypothalamic control of metabolic demand and supply. In this article, we review the functional and anatomical links between the stress neuroendocrine axis and the medullary network regulating breathing. We then present the persistent and sex-specific effects of neonatal stress on respiratory control in adult rats. The similarities between the respiratory phenotype of stressed rats and clinical manifestations of respiratory control disorders such as sleep-disordered breathing and panic attacks are remarkable. These observations are in line with the scientific consensus that the origins of adult disease are often found among developmental and biological disruptions occurring during early life. These observations bring a different perspective on the structural hierarchy of respiratory homeostasis and point to new directions in our understanding of the etiology of respiratory control disorders. © 2021 American Physiological Society. Compr Physiol 11:1-38, 2021.