Sex differences in stress reactivity of hippocampal BDNF in mice are associated with the female preponderance of decreased locomotor activity in response to restraint stress

A Truncated Receptor TrkB Isoform (TrkB.T1) in Mechanisms of Genetically Determined Depressive-like Behavior of Mice

Depression is a mental disorder that significantly reduces quality of life, and the discovery of new drug targets is an urgent problem for modern neuroscience. Brain-derived neurotrophic factor (BDNF) and its receptors have been found to participate in mechanisms of depression and antidepressant drugs' action. In this study, we focused on a less-studied truncated isoform of receptor TrkB: TrkB.T1. Initially, we noticed that the level of TrkB.T1 is low in the hippocampus of Antidepressant-Sensitive Cataleptics (ASC) mice, which are characterized by genetically determined depressive-like behavior in contrast to "normal" C57BL/6J mice. Next, overexpression of TrkB.T1 receptor in hippocampal neurons of ACS mice was induced to clarify the role of this receptor in mechanisms of depressive-like behavior. TrkB.T1 overexpression lowered BDNF protein concentration in the hippocampus. On the behavioral level, TrkB.T1 overexpression severely decreased aggression and enhanced social behavior. Additionally, this excess of receptor TrkB.T1 slightly promoted anxiety and depressive-like behavioral traits without affecting learning and memory. Our results show that this TrkB isoform participates in the control of aggression, anxiety, and depressive-like behavior and in the regulation of BDNF system functioning in ASC mice (genetically predisposed to depressive-like behavior). Considering our findings, we believe that hippocampal receptor TrkB.T1 can be a drug target for the correction of behavioral pathologies.

Single-day and multi-day exposure to orogastric gavages does not affect intestinal barrier function in mice

Animals involved in common laboratory procedures experience minor levels of stress. The direct effect of limited amounts of stress on gastrointestinal function has not been reported yet. Therefore, this study aimed to assess the effect of single-day and multi-day orogastric gavages on gut physiology in mice. To this end, 12-wk-old female C57Bl6/J mice were randomized to receive treatment with sterile water (200 µL) delivered by orogastric gavages twice daily for a total of 1 or 10 day(s). Control animals did not receive any treatment. Subsequently, gastrointestinal function was assessed by measuring fecal pellet production. Furthermore, ex vivo intestinal barrier and secretory function of the distal colon, proximal colon, and terminal ileum were quantified in Ussing chambers. In mice, single-day gavages did neither influence corticosterone levels nor gastrointestinal function. In mice exposed to multi-day gavages, corticosterone levels were slightly but significantly increased compared with controls after 10 days of treatment. Gastrointestinal motor function was altered, as evidenced by increased fecal pellet counts and a small increase in fecal water content. However, exposure to repeated gavages did not lead to detectable alterations in gastrointestinal barrier function as quantified by the paracellular flux of the probe 4 kDa FITC-dextran as well as transepithelial resistance measurements. Thus, the administration of drugs via single-day or multi-day orogastric gavages leads to no or minor stress in mice, respectively. In both cases, it does not hamper the study of the intestinal barrier function and therefore remains a valuable administration route in preclinical pharmacological research.NEW & NOTEWORTHY Exposure of mice to serial orogastric gavages over the course of 10 days leads to a small but significant increase in plasma corticosterone levels, indicating the presence of a limited amount of stress that is absent after a single-day treatment. This minor stress after multi-day gavages results in increased fecal pellet production and fecal water content in exposed compared with nontreated mice but does not affect the intestinal barrier function in the distal colon, proximal colon, or terminal ileum.

Sex differences in systemic bone and muscle loss following femur fracture in mice

Fracture induces systemic bone loss in mice and humans, and a first (index) fracture increases the risk of future fracture at any skeletal site more in men than women. The etiology of this sex difference is unknown, but fracture may induces a greater systemic bone loss response in men. Also sex differences in systemic muscle loss after fracture have not been examined. We investigated sex differences in systemic bone and muscle loss after transverse femur fracture in 3-month-old male and female C57BL/6 J mice. Whole-body and regional bone mineral content and density (BMC and BMD), trabecular and cortical bone microstructure, muscle contractile force, muscle mass, and muscle fiber size were quantified at multiple time points postfracture. Serum concentrations of inflammatory cytokines (IL-1β, IL-6, and TNF-α) were measured 1-day postfracture. One day postfracture, IL-6 and Il-1B were elevated in fracture mice of both sexes, but TNF-α was only elevated in male fracture mice. Fracture reduced BMC, BMD, and trabecular bone microstructural properties in both sexes 2 weeks postfracture, but declines were greater in males. Muscle contractile force, mass, and fiber size decreased primarily in the fractured limb at 2 weeks postfracture and females showed a trend toward greater muscle loss. Bone and muscle properties recovered by 6 weeks postfracture. Overall, postfracture systemic bone loss is greater in men, which may contribute to sex differences in subsequent fracture risk. In both sexes, muscle loss is primarily confined to the injured limb and fracture may induce greater inflammation in males.

Development of a Cushion-Shaped Device to Induce Respiratory Rhythm and Depth for Enhanced Relaxation and Improved Cognition

Workplace stress is a pertinent problem in today's world. Preventing and overcoming stress is critical for a healthy lifestyle because it is linked to various health problems and can lead to poor work performance. Controlling your breathing is one of the most effective ways to promote relaxation. However, regulating one's breathing necessitates some training and is not something that everyone can do easily. As a result, we concentrated on the relaxing effect of breathing and developed a cushion-shaped device that displays the desired respiratory motion. We used the effect of inducing one's respiratory movements by watching others' respiratory movements. When the user hugged the device, it changed the user's respiratory rhythm and depth. We conducted a user study with this device, which revealed that presenting respiratory motion can induce the user's respiratory rhythm and depth without any pre-training. Furthermore, subjective evaluation and ECG data suggested that using this device during task breaks can improve the relaxation effect and thus task performance after the break.

Post-weaning Social Isolation in Male and Female Prairie Voles: Impacts on Central and Peripheral Immune System

The socially monogamous prairie vole (Microtus ochrogaster) offers a unique opportunity to examine the impacts of adolescent social isolation on the brain, immune system, and behavior. In the current study, male and female prairie voles were randomly assigned to be housed alone or with a same-sex cagemate after weaning (i.e., on postnatal day 21-22) for a 6-week period. Thereafter, subjects were tested for anxiety-like and depressive-like behaviors using the elevated plus maze (EPM) and Forced Swim Test (FST), respectively. Blood was collected to measure peripheral cytokine levels, and brain tissue was processed for microglial density in various brain regions, including the Nucleus Accumbens (NAcc), Medial Amygdala (MeA), Central Amygdala (CeA), Bed Nucleus of the Stria Terminalis (BNST), and Paraventricular Nucleus of the Hypothalamus (PVN). Sex differences were found in EPM and FST behaviors, where male voles had significantly lower total arm entries in the EPM as well as lower latency to immobility in the FST compared to females. A sex by treatment effect was found in peripheral IL-1β levels, where isolated males had a lower level of IL-1β compared to cohoused females. Post-weaning social isolation also altered microglial density in a brain region-specific manner. Isolated voles had higher microglial density in the NAcc, MeA, and CeA, but lower microglial density in the dorsal BNST. Cohoused male voles also had higher microglial density in the PVN compared to cohoused females. Taken together, these data suggest that post-weaning social housing environments can alter peripheral and central immune systems in prairie voles, highlighting a potential role for the immune system in shaping isolation-induced alterations to the brain and behavior.

Glucocorticoid modulation of synaptic plasticity in the human temporal cortex of epilepsy patients: Does chronic stress contribute to memory impairment?

OBJECTIVE

Memory impairment is common in patients with temporal lobe epilepsy and seriously affects life quality. Chronic stress is a recognized cofactor in epilepsy and can also impair memory function. Furthermore, increased cortisol levels have been reported in epilepsy patients. Animal models have suggested that aggravating effects of stress on memory and synaptic plasticity were mediated via glucocorticoids. The aim of this study was, therefore, to investigate the effect of glucocorticoid receptor (GR) modulation on synaptic plasticity in the human cortex of epilepsy patients.

METHODS

We performed field potential recordings in acute slices from the temporal neocortex of patients who underwent surgery for drug-resistant temporal lobe epilepsy. Synaptic plasticity was investigated by a theta-burst stimulation (TBS) protocol for induction of long-term potentiation (LTP) in the presence of GR modulators.

RESULTS

LTP was impaired in temporal cortex from epilepsy patients. Pretreatment of the slices with the GR antagonist mifepristone (RU486) improved LTP induction, suggesting that LTP impairment was due to baseline GR activation in the human cortex. The highly potent GR agonist dexamethasone additionally weakened synaptic strength in an activity-dependent manner when applied after TBS.

SIGNIFICANCE

Our results show a direct negative glucocorticoid effect on synaptic potentiation in the human cortex and imply chronic activation of GRs. Chronic stress may therefore contribute to memory impairment in patients with temporal lobe epilepsy. Furthermore, the activity-dependent acute inhibitory effect of dexamethasone suggests a mechanism of synaptic downscaling by which postictally increased cortisol levels may prevent pathologic plasticity upon seizures.

PPM1F in Dentate Gyrus Modulates Anxiety-Related Behaviors by Regulating BDNF Expression via AKT/JNK/p-H3S10 Pathway

Anxiety is a serious psychiatric disorder, with a higher incidence rate in women than in men. Protein phosphatase Mg2+/Mn2+-dependent 1F (PPM1F), a serine/threonine phosphatase, has been shown to have multiple biological and cellular functions. However, the effects of PPM1F and its neuronal substrates on anxiety remain largely unclear. In this study, we showed that chronic restraint stress (CRS) induced anxiety-related behaviors only in female mice, while acute restraint stress (ARS) produced anxiety-related behaviors in both male and female mice in light-dark and elevated plus maze tests and induced upregulation of PPM1F and downregulation of brain-derived neurotrophic factor (BDNF) expression in the hippocampus. Adeno-associated virus-mediated overexpression of PPM1F or conditional knockout of BDNF in dentate gyrus (DG) led to a more pronounced anxiety-related behavior in female than in male mice as indicated by the behavioral evaluations. Meanwhile, overexpression of PPM1F in the DG decreased total Bdnf exon-specific messenger RNA expression in the hippocampus with the decreased binding activity of phosphorylated H3S10 to its individual promoters in female mice. Furthermore, we identified that overexpression of PPM1F decreased the phosphorylation levels of AKT and JNK in the hippocampus of female mice. These results may suggest that PPM1F regulates anxiety-related behaviors by modulating BDNF expression and H3S10 phosphorylation-mediated epigenetic modification, which may be served as potentially pathological genes associated with anxiety or other mental diseases.

Exploratory study on neurochemical effects of low-intensity pulsed ultrasound in brains of mice

There is now a relatively large body of evidence suggesting a relationship between dysfunction of myelin and oligodendrocytes and the etiology of several neuropsychiatric disorders, including depression and schizophrenia, and also suggesting that ultrasound methods may alleviate some of the symptoms of depression. We have applied low-intensity pulsed ultrasound (LIPUS) to the brains of mice treated with the demyelinating drug cuprizone, a drug that has been used as the basis for a rodent model relevant to a number of psychiatric and neurologic disorders including depression, schizophrenia, and multiple sclerosis. Prior to conducting the studies in mice, preliminary studies were carried out on the effects of LIPUS in vitro in neuron-like SH-SY5Y cells and primary glial cells. In subsequent studies in mice, female C57BL/6 mice were restrained in plastic tubes for 20 min daily with the ultrasound transducer near the end of the tube directly above the mouse's head. LIPUS was used at an intensity of 25 mW/cm² once daily for 22 days in control mice and in mice undergoing daily repetitive restraint stress (RRS). Behavioral or neurochemical studies were done on the mice or the brain tissue obtained from them. The studies in vitro indicated that LIPUS stimulation at an intensity of 15 mW/cm² delivered for 5 min daily for 3 days in an enclosed sterile cell culture plate in an incubator increased the viability of SH-SY5Y and primary glial cells. In the studies in mice, LIPUS elevated levels of doublecortin, a marker for neurogenesis, in the cortex compared to levels in the RRS mice and caused a trend in elevation of brain levels of brain-derived neurotrophic factor in the hippocampus relative to control levels. LIPUS also increased sucrose preference (a measure of the attenuation of anhedonia, a common symptom of several psychiatric disorders) in the RRS model in mice. The ability of LIPUS administered daily to rescue damaged myelin and oligodendrocytes was studied in mice treated chronically with cuprizone for 35 days. LIPUS increased cortex and corpus callosum levels of myelin basic protein, a protein marker for mature oligodendrocytes, and neural/glial antigen 2, a protein marker for oligodendrocyte precursor cells, relative to levels in the cuprizone + sham animals. These results of this exploratory study suggest that future comprehensive time-related studies with LIPUS on brain chemistry and behavior related to neuropsychiatric disorders are warranted. Exploratory Study on Neurochemical Effects of Low Intensity Pulsed Ultrasound in Brains of Mice. Upper part of figure: LIPUS device and in-vitro cell experimental set-up. The center image is the LIPUS generating box; the image in the upper left shows the cell experiment set-up; the image in the upper right shows a zoomed-in sketch for the cell experiment; the image in the lower left shows the set-up of repetitive restraint stress (RRS) with a mouse; the image in the lower middle shows the set-up of LIPUS treatment of a mouse; the image in the lower right shows a zoomed-in sketch for the LIPUS treatment of a mouse.

Sex and Age Effects on Neurobehavioral Toxicity Induced by Binge Alcohol

Historically, most alcohol neurotoxicity studies were conducted in young adult males and focused on chronic intake. There has been a shift towards studying the effects of alcohol on the adolescent brain, due to alcohol consumption during this formative period disrupting the brain's developmental trajectory. Because the most typical pattern of adolescent alcohol intake is heavy episodic (binge) drinking, there has also been a shift towards the study of binge alcohol-induced neurobehavioral toxicity. It has thus become apparent that binge alcohol damages the adolescent brain and there is increasing attention to sex-dependent effects. Significant knowledge gaps remain in our understanding of the effects of binge alcohol on the female brain, however. Moreover, it is unsettling that population-level studies indicate that the prevalence of binge drinking is increasing among American women, particularly those in older age groups. Although study of adolescents has made it apparent that binge alcohol disrupts ongoing brain maturational processes, we know almost nothing about how it impacts the aging brain, as studies of its effects on the aged brain are relatively scarce, and the study of sex-dependent effects is just beginning. Given the rapidly increasing population of older Americans, it is crucial that studies address age-dependent effects of binge alcohol, and given the increase in binge drinking in older women who are at higher risk for cognitive decline relative to men, studies must encompass both sexes. Because adolescence and older age are both characterized by age-typical brain changes, and because binge drinking is the most common pattern of alcohol intake in both age groups, the knowledge that we have amassed on binge alcohol effects on the adolescent brain can inform our study of its effects on the aging brain. In this review, we therefore cover the current state of knowledge of sex and age-dependent effects of binge alcohol, as well as statistical and methodological considerations for studies aimed at addressing them.

Hippocampal subfield volumes and change in body mass over 12 months of treatment in first-episode schizophrenia spectrum disorders

In this study, we explored the relationship between baseline hippocampal subfield volumes and change in body mass over 12 months of treatment in 90 first-episode schizophrenia spectrum disorder patients (66 males, 24 females; mean age= 24.7 ± 6.8 years). Body mass index was assessed in patients at baseline, and at months 3, 6, 9 and 12. Hippocampal subfields of interest were assessed at baseline using a segmentation algorithm included in the FreeSurfer 6.0 software program. Linear regression revealed a significant interactive effect between sex and anterior hippocampus size as predictors of change in body mass over 12 months, adjusting for age, substance use, and treatment duration. In an exploratory post-hoc sub-analysis, partial correlations showed a significant association between weight gain and smaller CA1, CA3 and subiculum volumes in females, but not males, adjusting for age and substance use, with similar trends evident for the CA4 and presubiculum subfields. In conclusion, our findings suggest that smaller anterior hippocampal subfields at baseline are associated with the development of weight gain over the course of treatment in first-episode schizophrenia spectrum disorders in a sex-specific fashion. This may be related to the greater increase in body mass evident for female patients in our study.

Infrared Thermography Reveals Sex-Specific Responses to Stress in Mice

Psychogenic hyperthermia is a stress-related condition reported mostly in women. Neuroendocrine responses to stress in females differ from those in males, and these differences cannot be explained solely based on hypothalamic-pituitary-adrenal (HPA) axis activity. Here, we used infrared (IR) thermographic imaging to record changes in cutaneous temperature following two types of stressful experiences in female and male mice. Mice were exposed to either single-session restraint stress or vertical exploration (rearing) deprivation and were monitored for exploratory activity and IR surface thermal changes. Females displayed higher rearing activity than males during the dark phase of the light cycle. Both sexes showed similar plasma corticosterone (CORT) responses after a challenge with restraint and rearing deprivation. However, only females responded to rearing deprivation with increased cutaneous temperature in the head and back, and a reduced thermal response in the tail. Circulating CORT levels were not correlated with the thermal variations. These findings, for the first time, provide evidence for sex-specific cutaneous thermal responses to short-term stress in mice following transient vertical-activity deprivation that may mimic clinical psychogenic hyperthermia.

Making "Good" Choices: Social Isolation in Mice Exacerbates the Effects of Chronic Stress on Decision Making

Chronic stress can impact decision-making and lead to a preference for immediate rewards rather than long-term payoffs. Factors that may influence these effects of chronic stress on decision-making are under-explored. Here we used a mouse model to investigate the changes in decision-making caused by the experience of chronic stress and the role of social isolation in exaggerating these changes. To test decision-making, mice were trained to perform a Cost-Benefit Conflict (CBC) task on a T-maze, in which they could choose between a high-reward, high-risk alternative and a low-reward, low-risk alternative. Mice were either housed in groups or alone throughout the experiment. Both groups of mice underwent a seven-day period of repeated immobilization to induce chronic stress. Stress levels were confirmed using behavioral (open field test) and physiological (urine corticosterone ELISA) measures. We found a significant increase in frequency of high-risk decisions after exposure to chronic stress among both socially- and individually-housed mice. Crucially, socially-housed mice showed a significantly smaller increase in high-risk decision-making compared to singly-housed mice. These findings suggest that chronic stress leads to an increase in high-risk decision-making in mice, and that lack of social interaction may exacerbate this stress effect.

Genes known to escape X chromosome inactivation predict co-morbid chronic musculoskeletal pain and posttraumatic stress symptom development in women following trauma exposure

Co-morbid chronic musculoskeletal pain (CMSP) and posttraumatic stress symptoms (PTSS) are frequent sequelae of motor vehicle collision, are associated with greater disability than either outcome alone, and are more prevalent in women than men. In the current study we assessed for evidence that gene transcripts originating from the X chromosome contribute to sex differences in vulnerability to CMSP and PTSS after motor vehicle collision. Nested samples were drawn from a longitudinal study of African American individuals, and CMSP (0-10 numeric rating scale) and PTSS (impact of events scale, revised) outcomes were assessed 6 months following motor vehicle collision. Blood RNA were sequenced (n = 101) and the relationship between X chromosome mRNA expression levels and co-morbid CMSP and PTSS outcomes was evaluated using logistic regression analyses. A disproportionate number of peritraumatic X chromosome mRNA predicting CMSP and PTSS in women were genes previously found to escape X chromosome inactivation (11/40, z = -2.9, p = .004). Secondary analyses assessing gene ontology relationships between these genes identified an enrichment in genes known to influence neuronal plasticity. Further, the relationship of expression of two critical regulators of X chromosome inactivation, X-inactive specific transcript (XIST) and Yin Yang 1 (YY1), was different in women developing CMSP and PTSS. Together, these data suggest that X chromosome genes that escape inactivation may contribute to sex differences in vulnerability to CMSP and PTSS after motor vehicle collision.

Sex Differences in Synaptic Plasticity: Hormones and Beyond

Notable sex-differences exist between neural structures that regulate sexually dimorphic behaviors such as reproduction and parenting. While anatomical differences have been well-characterized, advancements in neuroimaging and pharmacology techniques have allowed researchers to identify differences between males and females down to the level of the synapse. Disparate mechanisms at the synaptic level contribute to sex-specific neuroplasticity that is reflected in sex-dependent behaviors. Many of these synaptic differences are driven by the endocrine system and its impact on molecular signaling and physiology. While sex-dependent modifications exist at baseline, further differences emerge in response to stimuli such as stressors. While some of these mechanisms are unifying between sexes, they often have directly opposing consequences in males and females. This variability is tied to gonadal steroids and their interactions with intra- and extra-cellular signaling mechanisms. This review article focuses on the various mechanisms by which sex can alter synaptic plasticity, both directly and indirectly, through steroid hormones such as estrogen and testosterone. That sex can drive neuroplasticity throughout the brain, highlights the importance of understanding sex-dependent neural mechanisms of the changing brain to enhance interpretation of results regarding males and females. As mood and stress responsivity are characterized by significant sex-differences, understanding the molecular mechanisms that may be altering structure and function can improve our understanding of these behavioral and mental characteristics.

Effects of Antipsychotic Drugs on the Epigenetic Modification of Brain-Derived Neurotrophic Factor Gene Expression in the Hippocampi of Chronic Restraint Stress Rats

Recent studies have shown that antipsychotic drugs have epigenetic effects. However, the effects of antipsychotic drugs on histone modification remain unclear. Therefore, we investigated the effects of antipsychotic drugs on the epigenetic modification of the BDNF gene in the rat hippocampus. Rats were subjected to chronic restraint stress (6 h/d for 21 d) and then were administered with either olanzapine (2 mg/kg) or haloperidol (1 mg/kg). The levels of histone H3 acetylation and MeCP2 binding at BDNF promoter IV were assessed with chromatin immunoprecipitation assays. The mRNA levels of total BDNF with exon IV, HDAC5, DNMT1, and DNMT3a were assessed with a quantitative RT-PCR procedure. Chronic restraint stress resulted in the downregulation of total and exon IV BDNF mRNA levels and a decrease in histone H3 acetylation and an increase in MeCP2 binding at BDNF promoter IV. Furthermore, there were robust increases in the expression of HDAC5 and DNMTs. Olanzapine administration largely prevented these changes. The administration of haloperidol had no effect. These findings suggest that the antipsychotic drug olanzapine induced histone modification of BDNF gene expression in the hippocampus and that these epigenetic alterations may represent one of the mechanisms underlying the actions of antipsychotic drugs.

Possible involvement of monoamine neurons in the emotional abnormality in Kir6.2-deficient mice

ATP-sensitive potassium (K_ATP) channels consist of two structurally different subunits: a pore-forming subunit of the Kir6.0-family (Kir6.1 or Kir6.2) and a regulatory sulfonylurea receptor subunit (SUR1, SUR2A or SUR2B). Although Kir6.2 is widely distributed in the brain, the mechanisms that underlie the impact of Kir6.2 on emotional behavior are not yet fully understood. To clarify the role of Kir6.2 in emotional behavior, in the present study, we investigated the behavioral characteristics of Kir6.2-knockout (Kir6.2^-/-) mice. Kir6.2^-/- mice showed impaired general behavior in a locomotor activity test and open field test. In addition, anxiety-like behavior was observed in the open field test, elevated plus-maze test and light-dark test. In particular, excessive anxiety-like behavior was observed in female Kir6.2^-/- mice. Moreover, we investigated whether Kir6.2 is expressed on monoamine neurons in the brain. Immunohistochemical studies showed that Kir6.2 was co-localized with tryptophan hydroxylase (TPH), a marker of serotonergic neurons, in dorsal raphe nuclei. Kir6.2 was also co-localized with tyrosine hydroxylase (TH), a marker of dopaminergic/noradrenergic neurons, in the ventral tegmental area and locus coeruleus. Next, we checked the protein levels of TH and TPH in the midbrain. Interestingly, TPH expression was significantly elevated in female Kir6.2^-/- mice. These results suggest that Kir6.2 in monoamine neurons, especially serotonergic neurons, could play a key role in emotional behavior.

Sex-dependent differences in voluntary physical activity

Numbers of overweight and obese individuals are increasing in the United States and globally, and, correspondingly, the associated health care costs are rising dramatically. More than one-third of children are currently considered obese with a predisposition to type 2 diabetes, and it is likely that their metabolic conditions will worsen with age. Physical inactivity has also risen to be the leading cause of many chronic, noncommunicable diseases (NCD). Children are more physically inactive now than they were in past decades, which may be due to intrinsic and extrinsic factors. In rodents, the amount of time engaged in spontaneous activity within the home cage is a strong predictor of later adiposity and weight gain. Thus, it is important to understand primary motivators stimulating physical activity (PA). There are normal sex differences in PA levels in rodents and humans. The perinatal environment can induce sex-dependent differences in PA disturbances. This Review considers the current evidence for sex differences in PA in rodents and humans. The rodent studies showing that early exposure to environmental chemicals can shape later adult PA responses are discussed. Next, whether there are different motivators stimulating exercise in male vs. female humans are examined. Finally, the brain regions, genes, and pathways that modulate PA in rodents, and possibly by translation in humans, are described. A better understanding of why each sex remains physically active through the life span could open new avenues for preventing and treating obesity in children and adults. © 2016 Wiley Periodicals, Inc.

Acute Psychosocial Stress Inhibits LH Pulsatility and Kiss1 Neuronal Activation in Female Mice

Psychosocial stress, such as isolation and restraint, disrupts reproductive neuroendocrine activity. Here we investigate the impact of psychosocial stress on luteinizing hormone (LH) pulses and gene expression and neuronal activation within Rfrp and Kiss1 cells in female mice. Mice were ovariectomized (OVX) and handled daily to habituate to the tail-tip blood collection procedure. Blood was collected every 5 minutes for 180 minutes for measurement of LH. After 90 minutes, stress animals were placed into restraint devices and isolated to new cages. No-stress control animals remained in their home cages. LH pulses occurred at regular intervals during the entire 180-minute sampling period in controls. In contrast, stress induced a rapid and robust suppression of pulsatile LH secretion. Stress reduced the frequency of pulses by 60% and diminished basal LH levels by 40%; pulse amplitude was unaffected. In a separate cohort of OVX females, brains were collected after 45, 90, or 180 minutes of stress or in no-stress controls. At all time points, stress induced a potent decrease in arcuate Kiss1 neuronal activation, using cfos induction as a marker, with a 50% to 60% suppression vs control levels, whereas Rfrp and cfos coexpression in the dorsal-medial nucleus was elevated after 45 minutes of stress. Although arcuate Kiss1 gene expression remained stable, Rfrp expression was elevated 20% after 180 minutes of stress. These findings demonstrate rapid suppression of LH pulsatile secretion by psychosocial stress, associated with reduced cfos induction in Kiss1 neurons and time-dependent increases in Rfrp neuronal activation and messenger RNA.

Sex differences in morphine-induced behavioral sensitization and social behaviors in ICR mice

Gender and genetic strain are two prominent variants that influence drug abuse. Although certain sex-related behavioral responses have been previously characterized in ICR mice, little is known about the effects of sex on morphine-induced behavioral responses in this outbred strain. Therefore, in this study, we investigated the sex differences of morphine-induced locomotion, anxiety-like and social behaviors in ICR mice. After morphine or saline exposure for four consecutive days (twice daily), increased locomotion, more time spent in the central area, as well as attenuated rearing and self-grooming behaviors were found in morphine-treated females in an open field; no differences were found in locomotion and the time spent in the central area between male and female controls. When interacting with the same-sex individuals, female controls were engaged in more social investigation, following, body contacting and self-grooming behaviors than controls; morphine exposure reduced contacting and self-grooming behaviors in females; in contrast, these effects were not found in males. These results indicate that female ICR mice are more prosocial and are more susceptible to morphine exposure than males.

Protective effect of young green barley leaf (Hordeum vulgare L.) on restraint stress-induced decrease in hippocampal brain-derived neurotrophic factor in mice

Background:

Many health experts support the hypothesis that stressful lifestyles are the leading cause of illness, like depression. Therefore, from the standpoint of preventive medicine, it is important to reduce stress. Young green barley leaves are a good natural source of vitamins and minerals, and their juice is widely consumed as a functional food for health reasons in Japan. This study investigated the protective effect of young green barley leaves for stress control.

Materials and Methods:

ICR outbred mice were exposed to 3-h sessions of restraint stress. Young green barley leaves (400 and 1,000 mg/kg) were administered orally 1 h before the sessions for 5 days. To analyze voluntary behavior, wheel-running activity was monitored during the dark period. Brain-derived neurotrophic factor (BDNF) messenger RNA (mRNA) expression in the whole hippocampus was measured by real-time quantitative polymerase chain reaction.

Results:

Restraint stress resulted in a significant decrease in voluntary wheel-running behavior, but this decrease was ameliorated by the administration of young green barley leaves. The leaves also enhanced the decreased levels of BDNF mRNA induced by restraint stress; in particular, a significant protective effect was shown in the exon IV variant as compared to vehicle control mice.

Conclusion:

The findings suggest that young green barley leaves have potent anti-stress properties, as evidenced by preventing decreases in the levels of voluntary wheel-running activity and hippocampal BDNF mRNA in response to restraint stress. Our findings support the possibility that supplementation with young green barley leaves might be beneficial for preventing stress-related psychiatric disorders like depression.

Sex differences in Alzheimer's disease risk: are we looking at the wrong hormones?

Two-thirds of individuals with Alzheimer's disease (AD) are women, owing largely to the fact that women outlive men (https://www.alz.org/downloads/facts_figures_2012.pdf). Women's increased longevity, however, is not sufficient to explain the fact that women are 1.5 times more likely than men to develop the disease (Gao et al., 1998). After age 80, the incidence of AD is much higher in women than in men, such that the proportion of women with AD is almost twice the proportion of men with the disease (e.g., Zandi et al., 2002; Plassman et al., 2007). Moreover, once diagnosed with AD, women decline more rapidly, both cognitively and functionally, compared to men (Ito et al., 2011; Tschanz et al., 2011).