Post-stress Cortisol Levels Research Articles

Impact of Stress Phenotype, Elevated Temperature and Bacterin Exposure on Male Atlantic Salmon (Salmo salar) Growth, Stress and Immune Biomarker Gene Expression.

In this study, post-smolt male Atlantic salmon, previously identified as low (LR) or high responders (HR) based on post-stress cortisol levels, had their head kidney and liver sampled at 12 and 20°C prior to injection (time 0) and after (i.e., at 12 and 24 hpi, respectively) they were injected with either Forte Micro (a multi-valent vaccine containing bacterin, to capture peak antibacterial responses) or an equal volume of phosphate-buffered saline (PBS). Real-time quantitative polymerase chain reaction (qPCR) was then used to measure the expression of 15 biomarker genes in the head kidney and 12 genes in the liver at each temperature/sampling point. Target transcripts were chosen that were related to growth, stress and innate antibacterial immune responses. Many temperature, phenotype and injection effects were found for individual genes within these 3 broad categories, and multivariate statistical analyses (i.e., PCA and PERMANOVA) were used to look for overall patterns in transcript expression. These analyses revealed that HR salmon at 20°C mounted a more robust response (p < 0.05) for the 10 head kidney immune-related transcripts when injected with Forte Micro than LR salmon. In contrast, the 7 liver stress-related transcripts displayed a greater response (p = 0.057) in LR vs. HR fish with Forte Micro at 12°C. Overall, while this research did find some differences between LR and HR fish, it does not provide strong (conclusive) evidence that the selection of a particular phenotype would have major implications for the health of salmon over the temperature range examined.

The correlation between stress response term babies with intrauterine growth restriction and adulthood disease theories.

Every year, 14 million babies are born with low birth weight (LBW) and/or intrauterine growth restriction (IUGR) in developing countries. In Sudan, 15-25% of all newborns are born with LBW, with half being Term-LBW. The importance of nutrition in the first 1000 days of life has been well demonstrated. Evidence links IUGR to various health and developmental disorders, and intrauterine programming of the hypothalamic-pituitary-adrenal (HPA) axis has been strongly suggested as a possible mechanism. Sudan has been listed among the lowest four countries regarding food security which has a massive impact on maternal and infant health. We hypothesize that infants who suffer from intrauterine growth retardation will have exaggerated physiological and behavioural responses to physical stressors. To compare T-LBW with T-NBW on (a) Salivary cortisol level at rest and after a physical stressor and (b) Behavioural response to physical stressors. Hospital-based matched case-control study. Cases were 65 T-LBW neonates, and controls were 67 T-NBW neonates matched for age 4-6 hours, gestational age, and mode of deliverymeasurements: Anthropometry, salivary samples for cortisol before and after heel prick, and behavioural ratings. Compared with controls, the IUGR neonates were lighter, shorter, and thinner (p <0.0001) and had lower basal cortisol levels (p <0.03). Following stressors, IUGR neonates had lower (p >0.0001) and inhibited cortisol response (p <0.02), and cried less vigorously (p <0.0001). All anthropometric measures were significantly and positively correlated with behavioural responses and pre- and post-stress cortisol levels. Stunting was more strongly associated with behavioural inhibition than wasting. The severity of intrauterine growth retardation correlated with behavioral and physiological inhibition, which can lead to the development of mismatch diseases such as allergies, autoimmune diseases, and conjunctive disorders.

Phenotypic stress response does not influence the upper thermal tolerance of male Atlantic salmon (Salmo salar).

Fish can be identified as either low responders (LR) or high responders (HR) based on post-stress cortisol levels and whether they exhibit a proactive or reactive stress coping style, respectively. In this study, male Atlantic salmon (Salmo salar) from 17 families reared at 9°C were repeatedly exposed to an acute handling stress over a period of four months, with plasma cortisol levels measured at 1h post-stress. Fish were identified as either LR or HR if the total Z-score calculated from their cortisol responses fell into the lower or upper quartile ranges, respectively; with intermediate responders (IR) classified as the remainder. Salmon characterized as LR, IR or HR were then subjected to an incremental thermal challenge, where temperature was raised at 0.2°C day-1 from their acclimation temperature (12°C) to mimic natural sea-cage farming conditions during the summer in Newfoundland. Interestingly, feed intake remained high up to 22°C, while previous studies have shown a decrease in salmon appetite after ∼16-18°C. After the first three mortalities were recorded at elevated temperature, a subset of LR and HR salmon were exposed to another acute handling stress event at 23.6°C. Basal and post-stress measurements of plasma cortisol, glucose and lactate did not differ between stress response phenotypes at this temperature. In the end, the average incremental thermal maximum (ITMax) of LR and HR fish was not different (25.1°C). In comparison, the critical thermal maximum (CTMax; temperature increased at 2°C h-1) of the remaining IR fish that had been held at 12°C was 28.5°C. Collectively, these results: 1) show that this population of Atlantic salmon is very thermally tolerant, and further question the relevance of CTMax in assessing responses to real-world temperature changes; and 2) indicate that characterization of stress phenotype at 9°C is not predictive of their stress response or survival at high temperatures. Therefore, selection of fish based on phenotypic stress response at low temperatures may not be beneficial to incorporate into Atlantic salmon breeding programs, especially if the goal is to improve growth performance and survival at high temperatures in sea-cages.

Cortisol Stress Reactivity to the Trier Social Stress Test in Obese Adults

Objective: Approximately 600 million adults worldwide suffer from obesity. In addition to individual’s eating behavior and lack of physical activity in the development of obesity and overweight, psychosocial stress as well as hormonal stress reactivity must also be considered as important contributing factors. In the current study we compared the cortisol stress response pathway in a psychosocial stress induction (Trier Social Stress Test; TSST) with obese individuals and normal-weight controls. Method: 32 obese individuals (17 females; mean age = 33.94 years, SD = 11.31 years) and 32 normal-weight controls (17 females; mean age = 29.09 years, SD = 10.46 years) underwent the TSST. The salivary cortisol responses and three appraisal questionnaires (Primary Appraisal Secondary Appraisal, Visual Analogue Scale, Trier Inventory for Chronic Stress) were measured. Results: After stress induction, there was a significant main group difference between the obese individuals and the normal-weight controls for cortisol, with lower baseline and post-stress cortisol levels in the obese individuals. Nevertheless, the obese individuals as well as the normal-weight controls showed no significant difference in the self-reported assessment of the stress condition but some significant differences in the cognitive appraisal of the TSST. Conclusion: In conclusion, the induction of psychosocial stress showed differences in the cortisol patterns between the obese individuals and the normal-weight controls. Furthermore, the present data suggest that obesity leads to lower cortisol activity, which may indicate alterations in the Hypothalamic-pituitary-adrencortical (HPA) axis.

HPI reactivity does not reflect changes in personality among trout introduced to bold or shy social groups

Physiological stress responses often correlate with personalities (e.g., boldness). However, this relationship can become decoupled, although the mechanisms underlying changes in this relationship are poorly understood. Here we quantify (1) how an individual’s boldness (response to novel objects) in rainbow trout,Oncorhynchus mykiss, changes in response to interactions with a population of either bold or shy conspecifics and we (2) measured associated post-stress cortisol levels. Initially-bold trout became shyer regardless of group composition, whereas shy trout remained shy demonstrating that bold individuals are more plastic. Stress-induced plasma cortisol reflected the original personality of fish but not the personality induced by the treatment, irrespective of population personality. Change in boldness of bold trout may indicate preference towards initially subordinate behaviour when joining a new population. However, here we provide further evidence that behavioural and physiological parameters of coping styles may become uncoupled whereby behavioural changes are not correlated with stress responsiveness.

Reunion behavior after social separation is associated with enhanced HPA recovery in young marmoset monkeys

The relationships that offspring develop with caregivers can exert a powerful influence on behavior and physiology, including the hypothalamic-pituitary-adrenal (HPA) axis. In many mammalian species, offspring-caregiver relationships are largely limited to interactions with mother. Marmoset monkeys receive care in early life from multiple classes of caregivers in addition to the mother, including fathers and siblings. We evaluated whether affiliative social interactions with family members in marmosets were associated with differences in cortisol reactivity to a short-term social separation stressor, and whether these variations in affiliative interactions upon reunion predicted how well marmosets subsequently regulated HPA axis function after cessation of the stressor. Marmosets were separated from the family for 8h at three developmental time points (6-, 12-, and 18-months of age), and interactions of the separated marmoset with the family group were recorded during reunion. Urinary cortisol was measured prior to social separation, every 2h during the separation, and on the morning after separation. Heightened cortisol reactivity during social separation did not predict affiliative social behavior upon reunion but higher rates of grooming and play behavior predicted enhanced HPA regulation. Marmosets with higher rates of grooming and play with family members upon reunion had post-stress cortisol levels closer to preseparation baseline than marmosets with lower rates of affiliative reunion behavior. Combined with previous research showing the early programming effects of social interactions with caregivers, as well as the buffering effect of a close social partner during stress, the current study highlights the high degree of behavioral and HPA adaptability to social stressors across development in marmoset monkeys.

Salivary cortisol levels are elevated in the afternoon and at bedtime in children with prenatal alcohol exposure

Prenatal alcohol exposure can cause dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis, which may underlie some of the behavioral and adaptive problems seen in individuals with Fetal Alcohol Spectrum Disorders (FASD). Infants prenatally exposed to alcohol show altered basal and post-stress cortisol levels, but it is unknown if this persists beyond 2 years of age. It is also unknown if cortisol levels can be normalized through intervention programs. In this study, we investigated the effects of a physical activity program for children with FASD to determine: 1) if HPA dysregulation persists in school-age children with FASD, and 2) the effect of our program on cortisol levels. Twenty six children (ages 6–14 years) with FASD participated in an 8 week motor skill development program. Salivary cortisol levels were measured in 24 children and compared at 4 time points: before, immediately after, 3 months, and 1 year after program completion. Cortisol levels were also compared to 32 control children to evaluate the long-term effects of prenatal alcohol exposure on HPA regulation. For each time point, saliva was collected on each of 2 days at 3 times in the diurnal cycle: awakening, after school, and just before bedtime. Cortisol levels were significantly higher in the afternoon and at bedtime in children with FASD with confirmed prenatal exposure to high levels of alcohol (alcohol exposure rank 4), compared with Control children or children with FASD with exposure to low or unknown levels of alcohol (alcohol exposure rank 3). The program did not significantly affect cortisol levels in children with FASD as a group. These results provide support for long-term effects of prenatal alcohol exposure on the HPA system in humans, which could increase vulnerability to mental health issues and diseases later in life.

The effect of tryptophan supplemented diets on brain serotonergic activity and plasma cortisol under undisturbed and stressed conditions in grouped-housed Nile tilapia Oreochromis niloticus

Tryptophan (TRP) supplemented diets have been shown to have therapeutic effects in farmed animals including fish by modulating the activity of the neurotransmitter serotonin (5-hydroxytryptamine; 5-HT). The effects reported in fish have been obtained using individually-housed fish and include a reduction in stress response, aggression and stress-induced anorexia. In land farmed animals, TRP supplemented diets have also been shown to improve meat quality as a result of reduced stress during slaughter while in fish no data is currently available. This study aims at investigating whether short-term supplementation with TRP supplemented diets changes brain serotonergic activity and the stress response associated with slaughter handling in grouped-housed Nile tilapia Oreochromis niloticus. Adult fish (n=108, 490.6±4.0g, 12 individuals per tank) were exposed to one of the three treatments (triplicates per treatment were used): control (0.48g/100g), TRP 4× (1.87g/100g) and TRP 10× (4.45g/100g) diets during 7days. Afterwards, half of the fish in each tank were subjected to an acute stressor consisting of a combination of crowding and chasing, just prior to slaughter. The other half of the fish represented undisturbed conditions. Blood and brain samples were collected for cortisol and serotonergic activity analyses, respectively. Flesh quality was also assessed in both undisturbed and stressed fish for all treatments by measuring muscle pH and rigor mortis over a 72h period. Results showed that the highest TRP supplemented diet (TRP 10×) induced a significant reduction in undisturbed plasma cortisol (10.57±2.71ng/ml) as compared to TRP 4× (24.93±3.19ng/ml) and control diets (18.69±2.94ng/ml) and no effect on post-stress cortisol levels. After stress, the major 5-HT metabolite (5-hydroxyindoleacetic acid, 5-HIAA) was higher in the TRP 10× (471.31±60.95ng/g) as compared to the other diets (TRP 4×: 313.52±30.12ng/g; control: 260.36±19.65ng/g). Stress before slaughter induced a significant increase in plasma cortisol (from 18.40±1.76ng/ml under undisturbed conditions to 80.34±7.16ng/ml), however, it was not sufficient to cause a faster deterioration of flesh quality. TRP supplement diets had also no effect on muscle pH and rigor mortis during the 72h observation period. In conclusion, this study showed that only the highest levels of supplementation (10× the control diet) affect serotonergic activity. However, these levels did not result in reduced stress responsiveness or improved flesh quality when an acute stressor is applied before slaughter. Therefore, these results underline the fact that effects of TRP on cortisol production are dose- and context-dependent, and further experiments are needed to determine under which conditions the optimal effect is obtained.

Cortisol Responses to Naturalistic and Laboratory Stress in Student Teachers: Comparison with a Non‐stress Control Day

Ambulatory assessments of hypothalamus-pituitary-adrenal axis responses to acute natural stressors yield evidence on stress regulation with high ecological validity. Sampling of salivary cortisol is a standard technique in this field. In 21 healthy student teachers, we assessed cortisol responses to a demonstration lesson. On a control day, sampling was repeated at analogous times. Additionally, the cortisol awakening response (CAR) was assessed on both days. Participants were also exposed to a laboratory stressor, the Trier Social Stress Test, and rated their individual levels of chronic work stress. In pre-to-post-stress assessment, cortisol levels declined after the lesson. However, post-stress cortisol levels were significantly higher compared with those on the control day. Also, the Trier Social Stress Test yielded higher cortisol responses when using the control day as reference baseline. Associations between the CAR and chronic stress measures were observed solely on the control day. There were no significant associations between cortisol responses to the natural and laboratory stressors. Our results indicate that a control day might be an important complement in laboratory but especially in ambulatory stress research. Furthermore, associations between chronic stress measures and the CAR might be obscured by acute stress exposure. Finally, responses to the laboratory stressor do not seem to mirror natural stress responses.

Pigments, Parasites and Personalitiy: Towards a Unifying Role for Steroid Hormones?

A surging interest in the evolution of consistent trait correlations has inspired research on pigment patterns as a correlate of behavioural syndromes, or “animal personalities”. Associations between pigmentation, physiology and health status are less investigated as potentially conserved trait clusters. In the current study, lice counts performed on farmed Atlantic salmon Salmo salar naturally infected with ectoparasitic sea lice Lepeophtheirus salmonis showed that individual fish with high incidence of black melanin-based skin spots harboured fewer female sea lice carrying egg sacs, compared to less pigmented fish. There was no significant association between pigmentation and lice at other developmental stages, suggesting that host factors associated with melanin-based pigmentation may modify ectoparasite development to a larger degree than settlement. In a subsequent laboratory experiment a strong negative correlation between skin spots and post-stress cortisol levels was revealed, with less pigmented individuals showing a more pronounced cortisol response to acute stress. The observation that lice prevalence was strongly increased on a fraction of sexually mature male salmon which occurred among the farmed fish further supports a role for steroid hormones as mediators of reduced parasite resistance. The data presented here propose steroid hormones as a proximate cause for the association between melanin-based pigmentation and parasites. Possible fundamental and applied implications are discussed.

Neural plasticity is affected by stress and heritable variation in stress coping style

Here we use a comparative model to investigate how behavioral and physiological traits correlate with neural plasticity. Selection for divergent post-stress cortisol levels in rainbow trout (Oncorhynchus mykiss) has yielded low- (LR) and high responsive (HR) lines. Recent reports show low behavioral flexibility in LR compared to HR fish and we hypothesize that this divergence is caused by differences in neural plasticity. Genes involved in neural plasticity and neurogenesis were investigated by quantitative PCR in brains of LR and HR fish at baseline conditions and in response to two different stress paradigms: short-term confinement (STC) and long-term social (LTS) stress. Expression of proliferating cell nuclear antigen (PCNA), neurogenic differentiation factor (NeuroD) and doublecortin (DCX) was generally higher in HR compared to LR fish. STC stress led to increased expression of PCNA and brain-derived neurotrophic factor (BDNF) in both lines, whereas LTS stress generally suppressed PCNA and NeuroD expression while leaving BDNF expression unaltered. These results indicate that the transcription of neuroplasticity-related genes is associated with variation in coping style, while also being affected by STC – and LTS stress in a biphasic manner. A higher degree of neural plasticity in HR fish may provide the substrate for enhanced behavioral flexibility.

Linking Fearfulness and Coping Styles in Fish

Consistent individual differences in cognitive appraisal and emotional reactivity, including fearfulness, are important personality traits in humans, non-human mammals, and birds. Comparative studies on teleost fishes support the existence of coping styles and behavioral syndromes also in poikilothermic animals. The functionalist approach to emotions hold that emotions have evolved to ensure appropriate behavioral responses to dangerous or rewarding stimuli. Little information is however available on how evolutionary widespread these putative links between personality and the expression of emotional or affective states such as fear are. Here we disclose that individual variation in coping style predicts fear responses in Nile tilapia Oreochromis niloticus, using the principle of avoidance learning. Fish previously screened for coping style were given the possibility to escape a signalled aversive stimulus. Fearful individuals showed a range of typically reactive traits such as slow recovery of feed intake in a novel environment, neophobia, and high post-stress cortisol levels. Hence, emotional reactivity and appraisal would appear to be an essential component of animal personality in species distributed throughout the vertebrate subphylum.

Cortisol response to stress is associated with myocardial remodeling in salmonid fishes

Cardiac disease is frequently reported in farmed animals, and stress has been implicated as a factor for myocardial dysfunction in commercial fish rearing. Cortisol is a major stress hormone in teleosts, and this hormone has adverse effects on the myocardium. Strains of rainbow trout (Oncorhynchus mykiss) selected for divergent post-stress cortisol levels [high responsive (HR) and low responsive (LR)] have been established as a comparative model to examine how fish with contrasting stress-coping styles differ in their physiological and behavioral profiles. We show that the mean cardiosomatic index (CSI) of adult HR fish was 34% higher than in LR fish, mainly because of hypertrophy of the compact myocardium. To characterize the hypertrophy as physiological or pathological, we investigated specific cardiac markers at the transcriptional level. HR hearts had higher mRNA levels of cortisol receptors (MR, GR1 and GR2), increased RCAN1 levels [suggesting enhanced pro-hypertrophic nuclear factor of activated T-cell (NFAT) signaling] and increased VEGF gene expression (reflecting increased angiogenesis). Elevated collagen (Col1a2) expression and deposition in HR hearts supported enhanced fibrosis, whereas the heart failure markers ANP and BNP were not upregulated in HR hearts. To confirm our results outside the selection model, we investigated the effect of acute confinement stress in wild-type European brown trout, Salmo trutta. A positive correlation between post-stress cortisol levels and CSI was observed, supporting an association between enhanced cortisol response and myocardial remodeling. In conclusion, post-stress cortisol production correlates with myocardial remodeling, and coincides with several indicators of heart pathology, well-known from mammalian cardiology.

FC14-02 - Biological stress markers, executive functions and self-perceived stress in adults with ADHD (attention-deficit /hyperactivity disorder)

IntroductionThe management of normal daily tasks may be complicated for adults with ADHD (attention-deficit/hyperactivity disorder) due to executive dysfunctions. ADHD may thus increase the risk of chronic stress in everyday life.ObjectiveTo study endocrinological and psycho physiological stress markers in adults with ADHD in association to performance in test of executive functions (EF) and self-perceived stress.MethodsCardiovascular stress markers were assessed in 30 adults with ADHD with no psychoactive medication, and 30 healthy controls during: (1) non-stress baseline; (2) cognitive stress; and (3) non-stress recovery. The Visual Analogues Scale was used to assess self-perceived stress. Salivary cortisol was measured pre- and post-experiment. To measure stress in everyday life we assessed diurnal cortisol values, stressors and self-ratings of stress.ResultsThe group with ADHD showed higher self-perceived stress but attenuated or atypical cardiovascular stress reactivity during experimentally induced stress, and stress reactivity predicted performance in the executive test. Baseline cardiovasular values did not differ from the controls. The diagnosis of ADHD significantly increased the risk of belonging to the group with high post-stress cortisol levels. The two groups were comparable with respect to overall diurnal cortisol levels and rhythm. The ADHD group reported significantly higher self-perceived stress and these values correlated with level of stressors in everyday life.ConclusionsThe overall baseline values in biological stress markers may be comparable between adults with ADHD and healthy controls, while the stress reactivity and recovery pattern may differ between the two groups.

Nicotine as a Factor in Stress Responsiveness Among Detoxified Alcoholics

The effect of transdermal nicotine on stress reactivity was investigated in currently smoking, detoxified, substance-dependent individuals (65% alcohol dependent, n = 51; 31 male) following a psychosocial stressor. Using a randomized, double-blind, placebo-controlled design, subjects were assigned to receive either active transdermal nicotine (low or high dose) or placebo. Six hours following nicotine administration, subjects performed a laboratory psychosocial stressor consisting of two 4-min public-speaking sessions. Consistent with prior reports, substance-dependent individuals displayed a blunted stress response. However, a review of the cortisol distribution data encouraged additional analyses. Notably, a significant minority of the substance-dependent individuals (33%) demonstrated elevated poststress cortisol levels. This group of responders was more likely to be alcohol dependent and to have received the high dose of nicotine [χ2(2) = 32, P < 0.0001], [χ2(2) = 18.66, P < 0.0001]. Differences in salivary cortisol responses between responders and nonresponders could not be accounted for by the length of sobriety, nicotine withdrawal levels, anxiety or depressive symptomatology at the time of the psychosocial stressor. These results suggest that nicotine administration may support a normalization of the salivary cortisol response following psychosocial stress in subgroups of substance-dependent individuals, particularly those who are alcohol dependent. Given the association between blunted cortisol levels and relapse, and the complex actions of nicotine at central and peripheral sites, these findings support the systematic study of factors including nicotine, which may influence stress reactivity and the recovery process in alcohol-dependent individuals.

High self-perceived stress and many stressors, but normal diurnal cortisol rhythm, in adults with ADHD (attention-deficit/hyperactivity disorder)

Attention-deficit/hyperactivity disorder (ADHD) in adults is associated with significant impairment in many life activities and may thus increase the risk of chronic stress in everyday life. We compared adults with a DSM-IV ADHD diagnosis ( n = 28) with healthy controls ( n = 28) regarding subjective stress and amounts of stressors in everyday life, diurnal salivary cortisol in the everyday environment and salivary cortisol before and after cognitive stress in a laboratory setting. The association between cortisol concentrations and impulsivity was also investigated. Consistent with assumptions, individuals with ADHD reported significantly more self-perceived stress than controls, and subjective stress correlated with the amount of stressors in everyday life. The two groups were comparable with respect to overall diurnal cortisol levels and rhythm, as well as in pre- and post-stress cortisol concentrations. Post-stress cortisol (but not baseline cortisol) concentration was positively correlated with impulsivity. The group with high post-stress cortisol also reported more symptoms of depression and anxiety, as well as self-perceived stress and stressors in every-day life. The diagnosis of ADHD significantly increased the risk of belonging to the group with high post-stress cortisol levels. The results in this study warrant a focus not only on the primary diagnosis of ADHD, but also calls for a broader assessment of stressors and subjective stress in everyday life, as well as support comprising stress management and coping skills.

Hypothalamic–pituitary–adrenal (HPA) axis function in 3-month old infants with prenatal selective serotonin reuptake inhibitor (SSRI) antidepressant exposure

Background Prenatal exposure to stress and selective serotonin reuptake inhibitors (SSRIs) alter hypothalamic–pituitary–adrenal (HPA) stress reactivity in offspring, however, the effects of combined exposure to HPA activity in human infants is unknown. Objective To examine HPA basal levels and stress responsiveness in 3-month olds with prenatal exposure to SSRIs. Methods Salivary cortisol levels in infants of SSRI treated mothers ( n = 31, mean exposure 230.2 ± 72.2 days) were compared with non-SSRI exposed ( n = 45) infants in response to a challenge (infant-controlled habituation task) and under basal conditions in the late afternoon/early evening. Mode of feeding, to account for possible postnatal drug exposure via breast milk, as well as measures of pre and postnatal maternal mood, were included as covariates. Results Lower post-stress cortisol levels were observed in non-SSRI exposed/non-breastfed infants compared with non-SSRI exposed infants who were breastfed at 3 months of age. Stress reactivity patterns among SSRI exposed infants did not differ with mode of feeding. The cortisol reactivity slope (CRS) was significantly lower among non-SSRI exposed non-breastfed infants compared with non-SSRI exposed breastfed infants. Early evening basal cortisol levels were lower in SSRI exposed infants than in non-SSRI exposed infants, controlling for maternal mood and mode of feeding. Postnatal SSRI exposure (infant SSRI drug levels) via breast milk was not associated with stress or basal cortisol levels. Total cortisol, reflected by the AUC measure, did not differ significantly between exposure groups. Conclusions Prenatal SSRI exposure altered HPA stress response patterns and reduced early evening basal cortisol levels. Stress challenge HPA response differences only became apparent when the moderating effect of method of feeding was accounted for. These findings suggest an early “programming” effect of antenatal maternal mood, prenatal SSRI exposure and postnatal maternal care giving on the HPA system.

Behavioral plasticity in rainbow trout (O ncorhynchus mykiss) with divergent coping styles: When doves become hawks

Consistent and heritable individual differences in reaction to challenges, often referred to as stress coping styles, have been extensively documented in vertebrates. In fish, selection for divergent post-stress plasma cortisol levels in rainbow trout ( Oncorhynchus mykiss) has yielded a low (LR) and a high responsive (HR) strain. A suite of behavioural traits is associated with this physiological difference, with LR (proactive) fish feeding more rapidly after transfer to a new environment and being socially dominant over HR (reactive) fish. Following transport from the UK to Norway, a switch in behavioural profile occurred in trout from the 3rd generation; HR fish regained feeding sooner than LR fish in a novel environment and became dominant in size-matched HR–LR pairs. One year after transport, HR fish still fed sooner, but no difference in social dominance was found. Among offspring of transported fish, no differences in feeding were observed, but as in pre-transported 3rd generation fish, HR fish lost fights for social dominance against size-matched LR opponents. Transported fish and their offspring retained their distinctive physiological profile throughout the study; HR fish showed consistently higher post-stress cortisol levels at all sampling points. Altered risk-taking and social dominance immediately after transport may be explained by the fact that HR fish lost more body mass during transport than did LR fish. These data demonstrate that some behavioural components of stress coping styles can be modified by experience, whereas behavioural plasticity is limited by genetic effects determining social position early in life story.

Detection of QTL influencing cortisol levels in rainbow trout (Oncorhynchus mykiss)

Genetic variation in sensitivity to stress is a major determinant of production and welfare of aquaculture species. We investigated the genetics of the stress response using rainbow trout (Oncorhynchus mykiss) clonal lines with differing levels of domestication. First, we compared levels of cortisol among three clonal lines: two derived from highly domesticated populations (Arlee and OSU) and one from a population recently taken into captivity (Swanson). The Arlee clonal line showed significantly reduced cortisol levels in response to a netting stressor relative to the OSU and Swanson clonal lines. Next, we used interval mapping and composite interval mapping to scan the genome for quantitative trait loci (QTL) influencing post-stress cortisol levels in doubled haploid offspring of an OSU × Arlee hybrid and compared these to QTL for body mass. Two significant QTL with opposing additive effects on cortisol levels were detected, explaining 43% of the phenotypic variation. Two QTL were also detected for juvenile body mass, one of which overlapped with a QTL for cortisol levels on linkage group OA-XXVII, indicating a possible genetic link between these traits. However, the additive effects of these overlapping QTL suggest a positive relationship between cortisol levels and growth rate rather than the expected negative relationship. Our findings suggest complex genetic control of stress physiology and its relationship with growth rate.

Effects of stress on growth, cortisol and glucose levels in non-domesticated Eurasian perch ( Perca fluviatilis) and domesticated rainbow trout ( Oncorhynchus mykiss)

Eurasian perch ( Perca fluviatilis) is a promising aquaculture candidate, but the growth performance of this non-domesticated species may be negatively affected by its stress responsiveness to intensive culture conditions. To evaluate this potential problem, juvenile Eurasian perch were exposed to a standardized handling stressor twice a week for an 8-week period. A similar study was conducted on domesticated rainbow trout ( Oncorhynchus mykiss) for comparison of intra- and inter-specific differences. The stressed fish of both species showed lower body growth than the non-stressed control fish, however, the final mean body mass was 35.4% lower in the stressed Eurasian perch than in the non-stressed controls, compared to 22.8% difference between the two groups in rainbow trout. The stress responsiveness was examined by comparing the post-stress cortisol and glucose levels in repeatedly stressed fish and fish exposed to the stressor only once. The cortisol stress response in both species strongly indicated a habituation to the repeated stressor. Thus, repeatedly stressed Eurasian perch reached maximum cortisol levels of 130 ng/mL after 0.5 h compared to 200 ng/mL in the fish stressed once, while considerably smaller differences in cortisol levels were shown between the repeatedly and single stressed rainbow trout. Rainbow trout also showed lower post-stress glucose levels in the repeatedly stressed fish compared to the single stressed fish. In contrast, the glucose levels in both groups of Eurasian perch increased abruptly after stress treatment and remained elevated at approximately 19 mM for 6 h; levels were three times as high as the peak levels 3 h post-stress in rainbow trout. Together, the habituation of the stress response shown in both species did not eliminate the growth difference found in the repeatedly stressed fish versus the control fish. Further, the lower growth performance of Eurasian perch compared to rainbow trout could partly be due to the increased energy consumption in the more stress responsive Eurasian perch.