High Levels Of Stress Hormones Research Articles

Commentary: The devastating effects of ignoring child maltreatment in psychiatry--a commentary on Teicher and Samson 2016.

Despite the numerous studies over the past 30 years that have clarified the devastating effects of child maltreatment on mental and physical health, the role of trauma within the caregiving system remains unrecognized both in our diagnostic systems and in our dominant treatment paradigms. Research of people with histories of caregiver abuse and neglect consistently demonstrates problems with concentration, anger, panic, depression, food intake, drugs, and sleep, as well as decreased Heart RateVariability, higher levels of stress hormones, and reduced or impaired immune response. Their relationship between documented brain changes and psychopathology is complex. Traumatic life experiences during childhood and adolescence are far more common than expected. The Centers for Disease Control and Prevention estimates that child maltreatment may be the most costly public health issue in the United States, Eradicating child abuse in America wouldreduce the overall rate of depression by more than half, alcoholism by two-thirds, and suicide, serious drug abuse, and domestic violence by three quarters. It would also have a significantly positive effect on workplace performance, and vastly decrease the need forincarceration. The current practice of applying multiple distinct comorbid diagnoses to traumatized children prevents a comprehensive treatment approach. Approaching their problems from a framework of memories of discreet traumatic ignores the fact that the damage affects the brain's neural circuitry and goes well beyond dealing with discrete painful events. Our great challenge is to learn to utilize the brain's neuroplasticity to reorganize defective brain circuits.

Emotional memory in pregnant women at risk for postpartum depression

Postpartum depression (PPD) is associated with debilitating effects on mothers and their infants. A previous history of depression is considered the strongest risk factor for PPD. Depressed individuals recall more negative than positive content and higher levels of stress hormones released during encoding are associated with enhanced recall of emotional stimuli. This study examined the impact of a previous history of major depressive disorder (MDD) and pregnancy on emotional memory. Seventy-seven participants completed the study [44 pregnant women in the second trimester of pregnancy with and without a lifetime history of MDD and 33 non-pregnant women with and without a lifetime history of MDD]. All completed an encoding task and provided salivary cortisol (sCORT) and alpha-amylase (sAA) samples. Participants returned one week later for a surprise incidental recognition memory task. Women with a history of MDD had worse recognition than women without a history of MDD for negative, but not positive images; this effect was independent of sCORT and sAA levels. Pregnancy did not affect emotional memory. Considering that several previous studies found enhanced memory bias for negative content during depressive states, our results suggest that clinical remission may be associated with an opposite cognitive processing of negative emotional content.

The relationship of dominance, reproductive state and stress in female horses (Equus caballus)

Maintaining a dominant position in a hierarchy requires energetically expensive aggressive displays and physical exertion. Lab based winner–loser studies, often conducted with individuals from non-social species, have shown that subordinates have higher stress hormone levels than dominant individuals. However, in wild studies on cooperative breeders, displays of aggression used to maintain dominance status are associated with elevated stress hormone levels. The effect of reproductive state on dominance and stress has not been addressed within either of these situations. The purpose of this study was to examine physiological stress levels in relation to dominance rank and reproductive state in a non-cooperative breeder and herbivore, the domestic horse. The social interactions and measured faecal glucocorticoids were recorded in pastured, female horses that were either lactating or non-lactating. While faecal glucocorticoid metabolite level did not differ between reproductive state and rank, activity behaviour demonstrated significant differences between reproductive states. Higher energetic requirements of lactation were reflected in significantly longer bouts of eating and significantly less time spent alert and socializing. As non-cooperative breeders, the social nature of horses does not limit their reproduction or resource acquisition based upon rank, and therefore does not fit with the dominance-stress hypothesis or subordinate-stress hypothesis and instead supports a rank-independent stress hypothesis.

High stress hormone levels accelerate the onset of memory deficits in male Huntington's disease mice

Huntington's disease (HD) is a neurodegenerative disorder caused by a tandem repeat mutation in the huntingtin gene. Lifestyle factors, such as lack of activity may contribute to the variability in the age of disease onset. Therefore, better understanding of environmental modifiers may uncover potential therapeutic approaches to delay disease onset and progression.Recent data suggest that HD patients and transgenic mouse models show a dysregulated stress response. In this present study, we elevated stress hormone levels through oral corticosterone (CORT) treatment and assessed its impact on the development of motor impairment and cognitive deficits using the R6/1 transgenic mouse model of HD. We found that CORT consumption did not alter rotarod performance of R6/1 HD or wild-type (WT) littermates. However, the onset of hippocampal-dependent Y-maze deficits was accelerated in male R6/1 mice by 5days of CORT treatment, whereas short term memory of WT and female R6/1 mice was unaffected.We then further investigated the male HD susceptibility to CORT by measuring TrkB activation, BDNF and glucocorticoid receptor expression as well as the level of cell proliferation in the hippocampus. CORT treatment increased the levels of phosphorylated TrkB in male R6/1 mice only. There were no effects of CORT on hippocampal BDNF protein or mRNA levels; nor on expression of the glucocorticoid receptors in any group. Hippocampal cell proliferation was decreased in male R6/1 mice and this was further reduced in CORT-drinking male R6/1 mice. Female mice (WT and R6/1) appeared to be protected from the impacts of CORT treatment in all our hippocampal measures. Overall, our data demonstrate that treatment with corticosterone is able to modulate the onset of HD symptomatology.We present the first evidence of a male-specific vulnerability to stress impacting on the development of short-term memory deficits in HD. More generally, we found that female mice were protected from the detrimental effects of CORT treatment on a variety of hippocampus-based measures. Hippocampal plasticity and memory in HD may be more susceptible to the impacts of stress in a sex-dependent manner. We propose clinical investigations of stress as a key environmental modifier of HD symptom onset.

Does learning performance in horses relate to fearfulness, baseline stress hormone, and social rank?

The ability of horses to learn and remember new tasks is fundamentally important for their use by humans. Fearfulness may, however, interfere with learning, because stimuli in the environment can overshadow signals from the rider or handler. In addition, prolonged high levels of stress hormones can affect neurons within the hippocampus; a brain region central to learning and memory. In a series of experiments, we aimed to investigate the link between performance in two learning tests, the baseline level of stress hormones, measured as faecal cortisol metabolites (FCM), fearfulness, and social rank. Twenty-five geldings (2 or 3 years old) pastured in one group were included in the study. The learning tests were performed by professional trainers and included a number of predefined stages during which the horses were gradually trained to perform exercises, using either negative (NR) or positive reinforcement (PR). Each of the learning tests lasted 3 days; 7min/horse/day. The NR test was repeated in a novel environment. Performance, measured as final stage in the training programme, and heart rate (HR) were recorded. Faeces were collected on four separate days where the horses had been undisturbed at pasture for 48h. Social rank was determined through observations of social interactions during feeding. The fear test was a novel object test during which behaviour and HR were recorded.Performance in the NR and PR learning tests did not correlate. In the NR test, there was a significant, negative correlation between performance and HR in the novel environment (rS=−0.66, P<0.001, i.e. nervous horses had reduced performance), whereas there was no such correlation in the home environment (both NR and PR). Behavioural reactions in the fear test correlated significantly with performance in the NR test in the novel environment (e.g. object alertness and final stage: rS=−0.43, P=0.04), suggesting that performance under unfamiliar, stressful conditions may be predicted by behavioural responses in a fear test. There was a negative correlation between social rank and baseline stress hormones (rS=−0.43, P=0.04), i.e. high rank corresponded to low FCM concentrations, whereas neither rank nor FCM correlated with fearfulness or learning performance. We conclude that performance under stressful conditions is affected by activation of the sympathetic nervous system during training and related to behavioural responses in a standardised fear test. Learning performance in the home environment, however, appears unrelated to fearfulness, social rank and baseline FCM levels.

Life before birth: are the dice tossed for the rest of our lives?

Life before birth: are the dice tossed for the rest of our lives?

Performance, fatigue and stress in open-plan offices: The effects of noise and restoration on hearing impaired and normal hearing individuals

Hearing impaired and normal hearing individuals were compared in two within-participant office noise conditions (high noise: 60 L Aeq and low noise: 30 L Aeq ). Performance, subjective fatigue, and physiological stress were tested during working on a simulated open-plan office. We also tested two between-participants restoration conditions following the work period with high noise (nature movie or continued office noise). Participants with a hearing impairment (N = 20) were matched with normal hearing participants (N = 18) and undertook one practice session and two counterbalanced experimental sessions. In each experimental session they worked for two hours with basic memory and attention tasks. We also measured physiological stress indicators (cortisol and catecholamines) and self-reports of mood and fatigue. The hearing impaired participants were more affected by high noise than the normal hearing participants, as shown by impaired performance for tasks that involve recall of semantic information. The hearing impaired participants were also more fatigued by high noise exposure than participants with normal hearing, and they tended to have higher stress hormone levels during the high noise compared to the low noise condition. Restoration with a movie increased performance and motivation for the normal hearing participants, while rest with continued noise did not. For the hearing impaired participants, continued noise during rest increased motivation and performance, while the movie did not. In summary, the impact of noise and restorative conditions varied with the hearing characteristics of the participants. The small sample size does however encourage caution when interpreting the results.

Life at the top: rank and stress in wild male baboons.

In social hierarchies, dominant individuals experience reproductive and health benefits, but the costs of social dominance remain a topic of debate. Prevailing hypotheses predict that higher-ranking males experience higher testosterone and glucocorticoid (stress hormone) levels than lower-ranking males when hierarchies are unstable but not otherwise. In this long-term study of rank-related stress in a natural population of savannah baboons (Papio cynocephalus), high-ranking males had higher testosterone and lower glucocorticoid levels than other males, regardless of hierarchy stability. The singular exception was for the highest-ranking (alpha) males, who exhibited both high testosterone and high glucocorticoid levels. In particular, alpha males exhibited much higher stress hormone levels than second-ranking (beta) males, suggesting that being at the very top may be more costly than previously thought.

The role of stress in heart failure – ground for sex specific pathophysiology

In the last hundred years modern society went through numerous changes in life style, dietary habits, work load, physical activity and other environmental factors. As a species we are not well adapted to new de- mands. Higher levels of stress hormones provoke various effects, especially gradual change in the sensitivity of adrenergic, glucocorticoid and insulin receptors. All these changes are mutually associated and they gradually lead to metabolic syndrome, obesity, diabetes, heart failure and other types of pathology depending on genetic makeup and environmental factors. The aim of this paper is to summarize current knowledge concerning the impact of stress on cardiac function. Whereas stress response is sex specific we would emphasize a potential difference in pathophysiology of ischemic heart failure in men and women. Modern medicine has misinterpreted autonomous nervous system functions for years and this was reflected in heart failure (HF) and arterial hypertension therapy. Stress before the onset of menopause has a lesser effect on cardiac function compared to stress after menopause. Postmenopausal women have a significantly higher risk of heart disease, which is related to the diminished protection of the female hormonal cycle, but low doses of estrogen have not proven protective in postmenopausal women. Potential new targets of sex- specific cardiac therapy would come from better understanding of the molecular mechanisms exerted by nuclear receptors for steroid hormones, transcription factors involved in heart remodeling, cross-talk in adrenergic signaling pathways and their down-stream molecules.

Effect of Acute Posttrauma Propranolol on PTSD Outcome and Physiological Responses During Script‐Driven Imagery

Animal and human research suggests that the development of posttraumatic stress disorder (PTSD) may involve the overconsolidation of memories of a traumatic experience. Previous studies have attempted to use pharmaceutical agents, especially the β-adrenergic blocker propranolol, to reduce this overconsolidation. In this randomized, placebo-controlled study of the efficacy of propranolol in reducing the development of PTSD, we optimized dosages and conducted both psychophysiological and clinical assessments 1 and 3 months after the traumatic event. Forty-one emergency department patients who had experienced a qualifying acute psychological trauma were randomized to receive up to 240 mg/day of propranolol or placebo for 19 days. At 4 and 12 weeks post-trauma, PTSD symptoms were assessed. One week later, participants engaged in script-driven imagery of their traumatic event while psychophysiological responses were measured. Physiological reactivity during script-driven traumatic imagery, severity of PTSD symptoms, and the rate of the PTSD diagnostic outcome were not significantly different between the two groups. However, post hoc subgroup analyses showed that in participants with high drug adherence, at the 5-week posttrauma assessment, physiological reactivity was significantly lower during script-driven imagery in the propranolol than in the placebo subjects. The physiological results provide some limited support for a model of PTSD in which a traumatic conditioned response is reduced by posttrauma propranolol. However, the clinical results from this study do not support the preventive use of propranolol in the acute aftermath of a traumatic event.

DUCKLINGS STRESSED BY CHILLY INCUBATION

Most mums are determined to give their young the best start in life, and mother ducks are no exception. Settling down to incubate her eggs, an expectant mum will only move if it is absolutely necessary. However, even in the best case, this often means abandoning her eggs to feed for two brief periods a day. And stressed mothers may have to leave even more. According to William Hopkins, from Virginia Polytechnic Institute and State University, ducklings incubated by mums that take longer or more frequent breaks from the nest pay a price; they hatch with high levels of stress hormones. But without a direct route of communication between the mothers and their young, it wasn't clear why the ducklings were stressed and what affect it may have on their development. Then Hopkins' student, Sarah DuRant, had an idea: maybe the mother's brief absences were lowering the eggs' incubation temperatures and that was causing the ducklings stress. The duo decided to find out what effect low temperatures had on duckling stress and their development (p. 45).Hopkins and DuRant teamed up with duck expert Gary Hepp from Auburn University to collect freshly laid individual eggs from wild birds' nests before returning to Virginia Tech where they could be incubated. ‘Gary had published a study that demonstrated that very small changes in incubation temperature could affect the body size and composition of the hatchlings,’ explains Hopkins, so the team opted to incubate the eggs at 35, 35.9 and 37°C, all within the normal temperature range, and waited for them to hatch.The first thing that the team noticed was that the coolest eggs took longer to develop. ‘At low temperatures they take 37 days and at higher temperatures they take 31 days,’ says Hopkins, also the hatchlings looked perfectly normal, regardless of their incubation temperature, so the team moved the ducklings together into a room and monitored their development and stress hormone (corticosterone) levels.But within a few days, things started to go wrong for the cold incubated ducklings. Hopkins and DuRant carefully collected blood samples from the ducklings, analysed their corticosterone levels with Ignacio Moore and found that the resting cold incubated ducklings had higher stress hormone levels then the ducklings incubated at warmer temperatures. And when they tested the ducklings' reactions to stress they found that the cold incubated ducklings' hormone levels rocketed compared with those of the ducklings incubated at warmer temperatures. Incubation at a cooler temperature had increased the ducklings' stress hormone levels, but had this also affected other aspects of their biology?Monitoring the youngsters' growth, the team realised that the cold incubated ducklings failed to thrive. They grew slower than ducklings incubated at warmer temperatures and, even more surprisingly, the cold incubated ducklings began to die 4 or 5 days after hatching. ‘Normally most mortality occurs in the first couple of days after hatching,’ explains Hopkins, ‘but in the cold incubated chicks 75% of their mortality is after days 4 and 5, which suggests that there is a latent effect. Something is not right physiologically and causes the birds to fail to thrive’.Hopkins speculates that lower incubation temperatures delay the ducklings' development and this could prevent them from thriving. He also adds that this discovery could have an impact on avian ecologists. ‘What is interesting to me is that avian ecologists in the field look at hatching and fledging success, but that does not necessarily mean that you have a good understanding of the quality of the offspring. For that you need to monitor the young birds longer,’ says Hopkins.

Stress Questionnaires and Stress Biomarkers during Pregnancy

Both self-reported indicators of stress and hormones such as cortisol and corticotrophin-releasing hormone (CRH) have been examined in relation to preterm birth. Although these hormones have been interpreted as biomarkers of stress, it is unclear whether psychosocial measures are empirically associated with biomarkers of stress in pregnant women. We analyzed data from 1,587 North Carolina pregnant women enrolled in the Pregnancy, Infection,and Nutrition study during 2000-2004 who provided at least one saliva sample for cortisol measurement or blood samples for CRH at 14-19 and 24-29 weeks' gestation. Cortisol measures were limited to those taken between 8 and 10 a.m. Perceived stress, state-trait anxiety, coping style, life events, social support, and pregnancy-specific anxiety were measured by questionnaires and interviews. Spearman correlations and multiple regressions were used to describe the relationship among the measures of stress. No correlations larger than r = 0.15 were seen between reported psychosocial measures and cortisol or CRH. Women with demographic characteristics associated with poor pregnancy outcomes (unmarried, African-American, young, low pre-pregnancy body mass index) reported higher levels of stress but did not consistently have higher levels of stress hormones. Pre-eclampsia was associated with higher CRH, but not with higher cortisol. The relationship between measurements of reported stress and biomarkers is not straightforward in large epidemiological studies of pregnancy.

Effects of larval density on hematological stress indices in salamanders

In animals with complex life cycles, the quality of juvenile environments is important in shaping the longer-term fitness of individuals. Larval density is a major factor governing quality of larval environments in amphibians, with high densities leading to reduced growth rates, smaller size at metamorphosis, and potentially long-lasting postmetamorphic effects. A little-studied effect of larval density is its impact on physiological stress of postmetamorphic individuals. We used a hematological approach, involving counts of specific white blood cells types (neutrophils and lymphocytes) that covary with corticosterone, to estimate stress levels in recently metamorphosed spotted salamanders (Ambystoma maculatum) that were reared in three different larval densities in outdoor mesocosms. In replicated treatments consisting of 12, 25, or 50 larvae, survival was, as expected, lowest and size at metamorphosis smallest in the highest density mesocosms. In addition, surviving salamanders from high-density treatments had significantly higher neutrophil to lymphocyte ratios, indicative of high levels of stress hormones (corticosterone). This trend was not a result of density-related differences in body condition as these did not vary with density. Further, estimated stress levels were similar regardless of whether the salamanders metamorphosed early or late, suggesting that the density effect on stress is long-lasting even once realized density has been reduced through mortality or early metamorphosis. These results may be important in understanding amphibian population dynamics, since research on other vertebrate taxa demonstrates that high hematological stress indicators lead to reduced growth, survival, and increased disease susceptibility in vertebrate animals.

Comparing Retrobulbar and Topical Anaesthesia in Cataract Surgery by Phacoemulsification – How Can Patient Comfort During Surgery by Phacoemulsification Be Improved?

The first section of this article is a summary of the development of cataract surgery and the anaesthetic methods used in cataract surgery. When comparing the effectiveness of retrobulbar anaesthesia (RBA) and topical anaesthesia (TA), we found that more patients in the TA group indicated pain during the procedure (p&lt;0.001). After analysing pre-operative data, we could predict which patients would report intraoperative pain with 93% certainty. The type of anaesthesia and the skills of the surgeon are robust factors, while higher levels of stress hormones before surgery are also significant, especially in younger patients. The possible origin of pain and the role of positive verbal communication around the procedure are discussed. In order to prevent unexpected surgical situations, it is better to offer patients the most appropriate method of anaesthesia rather than using a ‘one size fits all’ solution.

Environmental enrichment, exercise and corticosterone affect endothelial cell proliferation in adult rat hippocampus and prefrontal cortex

Stress and environmental enrichment have opposing effects on cerebral cellular plasticity. Stress-induced disturbances in neuronal and glial plasticity have been implicated in the pathophysiology of affective disorders. Patients with depression often show volume reductions in specific brain regions. The mechanisms behind these changes are not well understood, but animal studies have indicated that increased levels of glucocorticoids and stress have negative impact on the neuronal and glial cell populations. On the contrary, enriched environment and physical activity have positive effects. In this study we have examined the effect of corticosterone (CORT), environmental enrichment (EE) and running on angiogenesis in hippocampus and prefrontal cortex (PFC). We demonstrate a dramatic inhibition in endothelial cell proliferation in these brain regions in CORT-treated rats. Environmental enrichment had the opposite effect and stimulated endothelial cell proliferation both in the hippocampus and in the PFC. Running had a stimulatory effect in hippocampus, but not in the PFC. We suggest that the angiostatic effect of CORT demonstrated in this study might be paralleled in human subjects exposed to high levels of stress hormones for prolonged periods of time. Raised cortisol levels in depressed or old patients could, by reducing endothelial cell formation/turnover, lead to rarefaction and aging of the vascular bed, and as a result, neuronal function could be impaired. It is tempting to speculate that a physically and intellectually active life may protect against stress-induced vascular changes. Therapeutic agents also targeting the cerebral vasculature could consequently constitute a new tool in the combat of stress-related disorders.

Altered hypothalamus–pituitary–adrenal gland axis regulation in the expanded CGG-repeat mouse model for fragile X-associated tremor/ataxia syndrome

The human FMR1 gene contains an unstable CGG-repeat in its 5' untranslated region. The repeat length in the normal population is polymorphic (5-54 CGG-repeats). Individuals carrying lengths beyond 200 CGGs (i.e. the full mutation) show hypermethylation and as a consequence gene silencing of the FMR1 gene. The absence of the gene product FMRP causes the fragile X syndrome, the most common inherited form of mental retardation. Elderly carriers of the premutation (PM), which is defined as a repeat length between 55 and 200 CGGs, can develop a progressive neurodegenerative syndrome: fragile X-associated tremor/ataxia syndrome (FXTAS). The high FMR1 mRNA levels observed in cells from PM carriers have led to the hypothesis that FXTAS is caused by a pathogenic RNA gain-of-function mechanism. Apart from tremor/ataxia, specific psychiatric symptoms have been described in PM carriers with or without FXTAS. Since these symptoms could arise from elevated stress hormone levels, we investigated hypothalamic-pituitary-adrenal (HPA) axis regulation using a knock-in mouse model with an expanded CGG-repeat in the PM range (>98 repeats) in the Fmr1 gene, which shows repeat instability, and displays biochemical, phenotypic and neuropathological characteristics of FXTAS. We show elevated levels of corticosterone in serum and ubiquitin-positive inclusions in both the pituitary and adrenal gland of 100-week-old animals. In addition, we demonstrate ubiquitin-positive inclusions in the amygdala from aged expanded CGG-repeat mice. We hypothesize that altered regulation of the HPA axis and the amygdala and higher stress hormone levels in the mouse model for FXTAS may explain associated psychological symptoms in humans.

Effects of stress and sex on acquisition and consolidation of human fear conditioning.

We examined the relationship between stress hormone (cortisol) release and acquisition and consolidation of conditioned fear learning in healthy adults. Participants underwent acquisition of differential fear conditioning, and consolidation was assessed in a 24-h delayed extinction test. The acquisition phase was immediately followed by an 11-min psychosocial stress period (arithmetic test combined with a public speech). Salivary cortisol was sampled at various time points before and after acquisition and retention of fear conditioning. Results showed two effects of endogenous cortisol. Post-acquisition cortisol correlated with fear acquisition in male but not female participants. In addition, post-acquisition cortisol correlated with consolidation of fear but only in those participants with high cortisol levels. We conclude that in the short term, a robust and sexually dimorphic relationship exists between fear learning and stress hormone levels. For those participants whose fear learning is accompanied by high stress hormone levels, a long-term relationship exists between cortisol release and memory consolidation. These short-term and long-term effects may relate to the differential involvement of mineralocorticoid and glucocorticoid receptor subtypes, respectively. The findings have implications for understanding the role of stress, sex, and hormones in different stages of fear learning and memory.

Increase in epinephrine excretion is associated with cognitive decline in elderly men: MacArthur studies of successful aging

High stress hormone levels are associated with increased risk of cognitive decline in elderly individuals. However, the effect of late-life changes in stress hormone levels on cognitive decline risk has not been examined. Our objective was to investigate whether increase over time in urinary epinephrine excretion in older adults was associated with subsequent cognitive decline. Measurements were made on 154 high-functioning men and women, 70-79 years of age, in 1988, 1991, and 1995. Twelve-hour overnight urinary excretion of epinephrine (normalized by creatinine excretion to adjust for body size) was recorded in 1988 and 1991. Cognitive functioning was assessed in 1991 and 1995 by summary scores based on standard tests of language, memory, abstraction, spatial recognition, and spatial construction. Compared to individuals whose epinephrine excretion decreased between 1988 and 1991, the individuals whose epinephrine excretion increased over the same period had greater subsequent declines in summary cognitive scores between 1991 and 1995. After adjusting for baseline epinephrine, baseline cognitive function, and relevant covariates, and stratifying by gender, increases in urine epinephrine were positively associated with cognitive decline only in men. We conclude that increase in urinary excretion of epinephrine predicts subsequent cognitive decline in older men.

Behavioral Changes Induced in Rats by Exposure to Trimethylthiazoline, a Component of Fox Odor.

Trimethylthiazoline (TMT), a component of fox feces, has been used in various studies as a natural predator stimulus to induce autonomic and behavioral signs of fear (e.g., higher levels of stress hormones, freezing, and risk assessment). The present study investigated whether 2 further behavioral signs of fear are induced in rats by TMT exposure: potentiation of the acoustic startle response and inhibition of appetitive behavior. In addition, the authors tested the rats for dose dependency of TMT-induced freezing behavior. The study confirmed that behavioral changes observed during TMT exposure are caused by TMT-induced fear and are dose dependent.

Long-haul brain drain

Too much jet setting can shrink your brain and impair your cognitive ability, according to new research by Kwangwook Cho [Nature Neurosci. (2001) 4, 567–568]. Brain scans showed that airline cabin crew who had less than five days to recover between long-haul flights had smaller right temporal lobes than those who were allowed longer recovery times. The short recovery group also performed worse on a spatial memory test that depends on the temporal lobe. The brain shrinkage was correlated with elevated levels of cortisol. Cho suggests that frequent shifts between time zones without sufficient time for readjustment disrupts the delicate relationship between the day–night cycle and our bodies’ circadian rhythms, leading to increased cortisol levels. As Cho explained to TICS, ‘disruption of circadian rhythms causes physiological and physical stress and high stress levels have an impact on brain function. Brain atrophy may be caused by high stress hormone levels.’ The airline crew study suggests that after five years of increased cortisol, cognitive deficits and brain shrinkage become apparent. HJB