Effects of continuous elevated cortisol concentrations during oestrus on concentrations and patterns of progesterone, oestradiol and LH in the sow

This study investigated the effect of continuous elevated cortisol concentrations during standing oestrus on time of ovulation and patterns of progesterone, oestradiol and luteinising hormone (LH) in sows. The elevation of cortisol concentrations was achieved through repeated intravenous injections of synthetic adrenocorticotropic hormone (ACTH) every 2 h for approximately 48 h, from the onset of the second standing oestrus after weaning. Treatment was terminated when ovulation was detected (monitored by transrectal ultrasonography every 4h) or when the sow had received a maximum of 24 injections. The dose of ACTH (2.5 microg/kg) was chosen to mimic the cortisol concentrations seen during mixing of unfamiliar sows. The sows (n=14) were surgically fitted with jugular vein catheters and randomly divided into a control (C group where only NaCl solution were injected) or an ACTH group. Blood samples were collected every 2 h. In parallel with the blood sampling, saliva samples for cortisol analyses were taken from eight sows before onset of treatment and from four of the sows during treatment. There was no difference in time from onset of standing oestrus to ovulation between the two groups. The interval between the peaks of oestradiol and LH to ovulation was prolonged in the ACTH group compared to the C group (p<0.05), with a tendency towards an earlier decline of oestradiol in the ACTH group. Cortisol and progesterone concentrations were significantly elevated during treatment in the ACTH group (p<0.001), with cortisol peak concentrations occurring between 40 and 80 min after each ACTH injection. Cortisol concentrations in saliva and plasma were highly correlated (p<0.001). In conclusion, elevated cortisol concentrations from the onset of standing oestrus increase progesterone concentrations and prolong the interval between oestradiol and LH peaks to ovulation, the latter possible due to an early decline in oestradiol concentrations and a change of the LH peak outline. The effect these hormonal changes have on reproductive performance need to be further investigated. Saliva samples might be a useful and non-invasive method to assess cortisol concentrations in sows.     

Effect of post-mating GnRH analogue (buserelin) treatment on PGF2alpha release in ewes and ewe lambs

The objectives of this study were to determine the effects of buserelin or saline treatment on ovarian function (Experiment 1), plasma PGFM concentrations and oxytocin stimulated prostaglandin F(2alpha) (PGF(2alpha)) release (Experiment 2) in ewe lambs and ewes. Welsh Halfbred ewes (n=26) and ewe lambs (n=24) were mated to vasectomised rams at synchronised oestrus and on Day 12 post-mating each animal was injected intramuscularly either normal saline or 4 microg buserelin. In Experiment 1, plasma progesterone and oestradiol concentrations were determined in samples collected by jugular venepuncture 1h before and at 0, 2, 4, 6, 8, 24, 48 and 72 h after treatment (n=7 per treatment group). Progesterone concentrations increased (P<0.05) from 2 to 8h after buserelin treatment and returned to basal levels after 72 h, whereas oestradiol concentrations were maximal at 2h post-treatment and returned to basal levels after 24h (P<0.05). Oestradiol concentrations were lower (P<0.05) in buserelin-treated animals than controls at 72 h post-treatment. Basal and post-treatment progesterone concentrations were greater (P<0.05) in ewes than in ewe lambs but oestradiol levels were similar for both age groups. Ovulation rate, determined by laparoscopy on Day 14, was similar for both age groups (ewes 1.1; ewe lambs 1.0). Buserelin treatment induced accessory corpora lutea in ewes (4/7; 57%) but not in ewe lambs (0/7; 0%). In the Experiment 2, plasma PGFM concentrations were determined in samples collected at 20-min intervals for 6h on Day 14 and at 20-min intervals for 1h before and at 10-min intervals for 1h and then at 20-min intervals for a further 3h period after an intravenous injection of oxytocin (1IU/kg body weight) on Day 15 post-oestrus. In this experiment there were five ewe lambs and six ewes per treatment group. There was no effect of buserelin treatment or age on basal PGFM concentrations on either Day 14 or 15. Although peak PGFM concentrations tended to be lower in buserelin-treated animals, the difference was not significant (P>0.05). However, peak duration following oxytocin challenge on Day 15 post-mating was shorter (P<0.05) in control ewes compared with control ewe lambs. In conclusion, buserelin treatment given on Day 12 post-oestrus enhances luteal function more in ewes than ewe lambs and after a transitory increase, reduces oestradiol concentrations in both ewes and ewe lambs. However, buserelin treatment does not significantly attenuate the luteolytic signal.     

Techniques for collecting saliva from awake, unrestrained, adult monkeys for cortisol assay

Cortisol levels serve as an index of pituitary-adrenal activity in nonhuman primates. In adult monkeys, cortisol is normally measured in blood (typically requiring restraint or sedation) or urine (reflecting a state rather than point estimate). In contrast, saliva collection is less invasive than drawing blood and allows for repeated sampling within a short period of time. Although protocols exist for collecting saliva from young monkeys, these procedures are inadequate for awake, unrestrained adult animals. Our laboratory has developed two methods for collecting saliva from adult rhesus monkeys: a "screen" method, which involves licking screen-covered gauze, and a "pole" method, which involves sucking and chewing on an attached rope. Twenty-three adult male rhesus monkeys were used to evaluate these two methods. After a period of adaptation, saliva samples were collected from 21 of 23 subjects. Saliva collection was faster with the pole than with the screen method (P < 0.01), but the pole method was not suitable for some animals because of their tendency to bite off the attached rope. An analysis of 19 saliva samples revealed a mean cortisol concentration of 0.84 microg/dl (range 0.27-1.77 microg/dl). There was no statistically significant difference in cortisol value between methods used (P > 0.22). The influence of the flavoring on the cortisol assay was tested, and was found to have no significant effect (P > 0.28). Our results indicate that either technique can be used to safely collect saliva from unrestrained adult monkeys. Choice of technique will depend on the proclivities of individual monkeys.     

Salivary and plasma cortisol response to adrenocorticotropin administration in pigs

Two experiments were conducted to determine the responsiveness of salivary and plasma cortisol to acute (i.v.), depot (i.m.) and chronic (repeated i.m.) adrenocorticotropin (ACTH) administration in swine. In Experiment 1, barrows (castrated pigs) were assigned to one of three injection treatments: (1) saline i.m. (SHAM1, n=2); (2) 0.75 IU/kg BW ACTH in saline i.v. (ACUTE, n=2); (3) 2.25 IU/kg BW ACTH in gel i.m. (DEPOT, n=3). Total cortisol concentrations were determined for concurrent saliva and blood samples. Correlations between salivary and plasma cortisol within treatments were: SHAM1, r=0.60; ACUTE, r=0.58; DEPOT, r=0.79. In Experiment 2, barrows were assigned to one of two injection treatments: (1) gel i.m. (SHAM2, n=3); (2) 2.25 IU/kg BW ACTH in gel i.m. (CHRONIC, n=4). The injections occurred every 6 h for a total of eight injections. Concurrent saliva and blood samples were obtained every 3 h for 72 h followed by an increasing sampling interval until day 6. Overall correlations between salivary and plasma cortisol were: SHAM2, r=0.30 and CHRONIC, r=0.61. Experiment 1 found that the relationship between salivary and plasma cortisol was stronger during longer (DEPOT) than shorter (ACUTE) ACTH stimulation. Experiment 2 found a strong relationship between the two measurements during chronic ACTH stimulation, but that relationship weakened after ACTH stimulation ceased.     

A re-investigation of saliva collection procedures that highlights the risk of potential positive interference in cortisol immunoassay

Background

The use of saliva for measurement of cortisol permits non-invasive study of adrenal function, but collection can be technically difficult, particularly in small infants. Saliva collection can be assisted by citric acid to increase saliva flow, or by the use of cotton or polyester swabs in the mouth.

Aim

To determine whether different methods of saliva collection affect cortisol radioimmunoassay (RIA) performance.

Experimental

Cortisol was measured in saliva collected from 16 adults using intra-oral cotton swabs or polyester swabs, compared with saliva dribbled directly into a pot either alone (plain saliva) or after citric acid had been placed on the tongue. An in-house RIA, without prior extraction, was used to measure cortisol with an encapsulated sheep antibody.

Results

Mean (median) salivary cortisol was 10.9 (10.5) nmol L⁻¹ in plain saliva, 10.4 (8.4) nmol L⁻¹ in citric acid stimulated saliva; 25.3 (25.1) nmol L⁻¹ in saliva collected on cotton swabs, and 27.9 (27.3) nmol L⁻¹ collected on polyester swabs. Cortisol in saliva collected using citric acid was not significantly different from plain saliva (p = 0.997), but cortisol in saliva collected using cotton and polyester swabs was significantly higher than that of plain saliva (p < 0.01).

Conclusion

The use of cotton or polyester swabs for collection of saliva can result in spuriously high levels of cortisol when measured by RIA.     

Development of Salivary Cortisol Circadian Rhythm and Reference Intervals in Full-Term Infants

BackgroundCortisol concentrations in plasma display a circadian rhythm in adults and children older than one year. Earlier studies report divergent results regarding when cortisol circadian rhythm is established. The present study aims to investigate at what age infants develop a circadian rhythm, as well as the possible influences of behavioral regularity and daily life trauma on when the rhythm is established. Furthermore, we determine age-related reference intervals for cortisol concentrations in saliva during the first year of life.Methods130 healthy full-term infants were included in a prospective, longitudinal study with saliva sampling on two consecutive days, in the morning (07:30-09:30), noon (10:00-12:00) and evening (19:30-21:30), each month from birth until the infant was twelve months old. Information about development of behavioral regularity and potential exposure to trauma was obtained from the parents through the Baby Behavior Questionnaire and the Life Incidence of Traumatic Events checklist.ResultsA significant group-level circadian rhythm of salivary cortisol secretion was established at one month, and remained throughout the first year of life, although there was considerable individual variability. No correlation was found between development of cortisol circadian rhythm and the results from either the Baby Behavior Questionnaire or the Life Incidence of Traumatic Events checklist. The study presents salivary cortisol reference intervals for infants during the first twelve months of life.ConclusionsCortisol circadian rhythm in infants is already established by one month of age, earlier than previous studies have shown. The current study also provides first year age-related reference intervals for salivary cortisol levels in healthy, full-term infants.     

Plasma cortisol and faecal cortisol metabolites concentrations in stereotypic and non-stereotypic horses: do stereotypic horses cope better with poor environmental conditions?

Background

Stereotypic behaviours, i.e. repetitive behaviours induced by frustration, repeated attempts to cope and/or brain dysfunction, are intriguing as they occur in a variety of domestic and captive species without any clear adaptive function. Among the different hypotheses, the coping hypothesis predicts that stereotypic behaviours provide a way for animals in unfavourable environmental conditions to adjust. As such, they are expected to have a lower physiological stress level (glucocorticoids) than non-stereotypic animals. Attempts to link stereotypic behaviours with glucocorticoids however have yielded contradictory results. Here we investigated correlates of oral and motor stereotypic behaviours and glucocorticoid levels in two large samples of domestic horses (N _Study1 = 55, N _Study2 = 58), kept in sub-optimal conditions (e.g. confinement, social isolation), and already known to experience poor welfare states. Each horse was observed in its box using focal sampling (study 1) and instantaneous scan sampling (study 2). Plasma samples (collected in study 1) but also non-invasive faecal samples (collected in both studies) were retrieved in order to assess cortisol levels.

Results

Results showed that 1) plasma cortisol and faecal cortisol metabolites concentrations did not differ between horses displaying stereotypic behaviours and non-stereotypic horses and 2) both oral and motor stereotypic behaviour levels did not predict plasma cortisol or faecal cortisol metabolites concentrations.

Conclusions

Cortisol measures, collected in two large samples of horses using both plasma sampling as well as faecal sampling (the latter method minimizing bias due to a non-invasive sampling procedure), therefore do not indicate that stereotypic horses cope better, at least in terms of adrenocortical activity.     

Social instability and immunity in rhesus monkeys: the role of the sympathetic nervous system

Social instability can adversely affect endocrine, immune and health outcomes, and recent evidence suggests that the sympathetic nervous system (SNS) might mediate these effects. We conducted two studies with adult male rhesus monkeys (Macaca mulatta) to understand how social conditions affect measures of SNS activity and immune function. In Experiment 1, animals were socialized in stable social conditions, then were switched to unstable (stressful) social conditions, then were returned to stable conditions. Analysis revealed quadratic effects for measures of behaviour, urinary metabolites of epinephrine and norepinephrine, and expression of immune response genes: as expected, social instability adversely impacted most measures, and the effects remediated upon re-imposition of stable conditions. Cortisol levels were unaffected. In Experiment 2, we used the sympathomimetic drug methamphetamine to challenge the SNS; animals also underwent socialization in stable or unstable groups. Surprisingly, while methamphetamine elevated plasma catecholamines, responses in lymph nodes tracked the social, and not the drug, condition: social instability upregulated the density of SNS fibres in lymph nodes and downregulated Type I interferon gene expression. Together, these results indicate that the SNS is extremely sensitive to social conditions; full understanding of the adverse effects of social instability on health should therefore incorporate measures of this health-relevant system.     

The hormonal content of the hypophyseal-adrenocortical system in the blood of the suslik Citellus undulatus at different seasons of the year

Radioimmune assay has been made of the content of ACTH and cortisol in the peripheral blood of the ground squirrel Citellus undulatus parryi at various seasons and during a short hibernation period. Within annual cycle, negative relationship was observed between ACTH and cortisol levels. Cortisol content decreases from Autumn to Winter; the content of ACTH in the blood plasma, measured during periodic arousals, increases progressively during hibernation. Concentration of both hormones significantly decreases in sleeping animals, increasing during arousals. At the beginning of hibernation period, cortisol content gradually decreases. During self-warming of arousing animals, cortisol content remains low. The decreased production of cortisol in hibernating animals is presumably associated with the increase in the threshold of sensitivity of the adrenal receptors to stimulating effect of ACTH. The role of glucocorticoids and ACTH in the metabolism of hibernating animals is discussed.     

Cortisol and β-endorphin levels in peripheral circulation around weaning in primiparous sows

Peripheral plasma patterns of cortisol and β-endorphin were compared around weaning in primiparous sows. Blood samples for hormone analysis were collected repeatedly on the day before weaning, on the day of weaning and on the day after weaning. Peak cortisol and β-endorphin levels occurred shortly after weaning on the day of weaning. Cortisol concentration on the day of weaning was greater (P < 0.001) than on the day before weaning, which in turn was higher (P < 0.05) than on the day after weaning. β-Endorphin concentrations on the day before weaning and on the day of weaning were similar, but were greater (P < 0.01) on both these days than on the day after weaning. Overall, cortisol and β-endorphin patterns followed a similar trend, which was more marked on the day before weaning and on the day of weaning than on the day after weaning. Pearson's correlation coefficients for peripheral plasma cortisol and β-endorphin secretion were 0.61 (P < 0.001) on the day before weaning, 0.63 (P < 0.001) on the day of weaning and 0.15 (P < 0.13) on the day after weaning. The present study indicates that suckling and weaning are stressful stimuli during which the peripheral plasma concentrations of cortisol and β-endorphin follow a similar trend.     

Effect of a topical anaesthetic formulation on the cortisol response to surgical castration of unweaned beef calves

Impracticality and cost of existing pain management strategies during surgical castration of beef cattle have limited their widespread implementation on-farm. A farmer-applied topical anaesthetic formulation, originally developed and used commercially to mitigate the pain of mulesing in lambs, was investigated for its potential use for managing pain in surgically castrated calves. This formulation contained lidocaine, bupivacaine, adrenalin and cetrimide. In this study, 24 Angus bull calves were randomly allocated to (1) surgical castration (C, n=8), (2) surgical castration with the post-operative application of topical anaesthetic (CTA, n=8) and (3) sham castration/control (CON, n=8). The experiment was conducted over 2 days, with treatment groups evenly represented across each day. Calves were habituated to handling before the experiment and blood samples were collected for plasma cortisol measurement at defined time periods before, at and post treatment, (at −0.5, 0 h, then +0.5, 1, 1.5, 2, 4 and 6 h). There was a significant effect of time on cortisol concentrations across all treatment groups (P<0.01), with lowest concentrations at −0.5 and 6 h and peak concentration at 0.5 h being significantly higher than the cortisol response at 0 h. The effect of treatment was not significant (P=0.077), however, there was a trend for CON calves to display lower cortisol concentrations than C and CTA calves and CTA calves to display lower cortisol concentrations than C calves. The mean area under the curve (AUC) of CON calves was significantly lower than those of C and CTA calves (P=0.04), however, there was no significant difference between the AUCs of CTA and C calves. Immediate application of topical anaesthetic after surgical castration did not significantly reduce plasma cortisol concentrations. However, the trend for CTA calves to display lower cortisol concentrations than C calves warrants further investigation into the use of TA for pain relief of surgically castrated beef calves.     

Evaluation of a method to measure long term cortisol levels

IntroductionElevated levels of cortisol are known to induce various symptoms and diseases, e.g. abdominal obesity, type 2 diabetes, osteoporosis and cardiovascular disease. Measuring serum, saliva and urine cortisol is limited to one time point. Measurement of cortisol in scalp hair is a recently developed method to measure long term cortisol levels. The aim of this study was to investigate whether hair cortisol is a feasible parameter to measure cortisol exposure.ExperimentalWe collected hair samples of 195 healthy individuals, 9 hypercortisolemic and one hypocortisolemic patient and measured hair cortisol levels. Cortisol was extracted from scalp hair using methanol and cortisol levels were measured using a salivary ELISA kit. Measurement of waist and hip circumferences and blood pressure was performed in 46 healthy subjects.ResultsWe found a positive correlation between hair cortisol and both waist circumference (r = 0.392, p = 0.007) and waist-to-hip ratio (WHR) (r = 0.425, p = 0.003). No correlations were found between hair cortisol levels and BMI, blood pressure or age. There was no decline in cortisol levels in six consecutive hair segments. Hair cortisol levels were elevated in patients with known hypercortisolism (p < 0.0001).ConclusionsHair cortisol was positively correlated with WHR, suggesting that hair cortisol reflects cortisol exposure at tissue level, which was also supported by elevated hair cortisol levels in hypercortisolemic patients and concordance between hair cortisol levels and clinical disease course. Cortisol levels in hair are slightly influenced by hair treatment but not by natural hair colour, use of hair products, gender or age.     

Mobbing vocalizations as a coping response in the common marmoset

Using a non-invasive method of sampling saliva followed by assay for cortisol levels, we found that common marmosets (Callithrix jacchus) show a decrease in cortisol levels after seeing a snake-model stimulus that reliably elicits mobbing (tsik) calls. In fact, there was a significant positive correlation between the number of tsik vocalizations made and the magnitude of the decrease in the cortisol concentrations. Furthermore, marmosets with higher levels of cortisol prior to being exposed to the stimulus produce more tsik calls than those with lower levels of cortisol. Subsequent experiments showed that, in response to 15 min of isolation with no visual or auditory contact with conspecifics (a traditional stressor), cortisol levels increased significantly. However, playback of the mobbing calls of a familiar conspecific to individual isolated marmosets not only prevented the rise in cortisol, but also actually caused a decrease in the levels of this hormone. This suggests that the mobbing calls serve to calm the marmoset after experiencing a stressful situation. This finding results in a greater understanding as to the role of physiological responses during communication in this species and could have implications for the welfare of marmosets in captivity.     

Effectiveness of saliva collection and enzyme-immunoassay for the quantification of cortisol in socially housed baboons

Circulating cortisol levels are often used to assess the biological stress response in captive primates. Some methods commonly used to collect blood samples may alter the stress response. As such, noninvasive means to analyze cortisol levels are increasingly being developed. We adapted an existing collection method to simultaneously obtain saliva from multiple socially living hamadryas baboons (Papio hamadryas hamadryas) and validated an enzyme-immunoassay kit to quantify cortisol within the saliva samples. Over a period of 12 months, saliva samples were regularly collected from approximately half of the 18-member colony, representing younger monkeys who were more willing to participate. The assay met the four criteria typically used to assess the effectiveness of a new analytical technique: parallelism, precision, accuracy, and sensitivity. Cortisol levels were also proportional to those expected given published plasma levels of cortisol in baboons. Further, salivary cortisol levels increased in individuals following significant stress-related events, such as removal from the group, indicating biological validation. The technique provided a reliable and effective means to assess a physiological indicator of stress in a social group without initiating a stress response owing to handling or sedation, and provided a real-time assessment of cortisol levels and reactivity.     

Scales Tell a Story on the Stress History of Fish

Fish faced with stressful stimuli launch an endocrine stress response through activation of the hypothalamic-pituitary-interrenal (HPI-) axis to release cortisol into the blood. Scientifically validated biomarkers to capture systemic cortisol exposure over longer periods of time are of utmost importance to assess chronic stress in governmental, wildlife, aquaculture and scientific settings. Here we demonstrate that cortisol in scales of common carp (Cyprinus carpio L.) is the long-sought biomarker for chronic stress. Undisturbed (CTR) and daily stressed (STRESS) carp were compared. Dexamethasone (DEX) or cortisol (CORT) fed fish served as negative and positive controls, respectively. Scale cortisol was quantified with a validated ultra-performance liquid chromatography tandem mass spectrometry method. An increase in scale cortisol content was found in STRESS and CORT but not in CTR and DEX fish. Scale cortisol content reflects its accumulation in a stressor and time dependent manner and validates the scale cortisol content as biomarker for chronic stress. Plasma analyses confirmed that (i) CTR, DEX and CORT treatments were effective, (ii) plasma cortisol of STRESS fish showed no signs of chronic HPI-axis activation, and (iii) plasma cortisol is a poor predictor for chronic stress. The expression of HPI key genes crf, pomc, and star were up-regulated in STRESS fish in the absence of a plasma cortisol response, as was the target gene of cortisol encoding subunit α1 of the Na⁺/K⁺-ATPase in gills. When lost, scales of fish regenerate fast. Regenerated scales corroborate our findings, offering (i) unsurpassed time resolution for cortisol incorporation and as such for stressful events, and (ii) the possibility to investigate stress in a well defined and controlled environment and time frame creating novel opportunities for bone physiological research. We conclude that the cortisol content in ontogenetic and regenerated scales is an innovative biomarker for chronic stress offering ample applications in science and industry.     

The development of cortisol metabolism in the perinatal period in the guinea-pig

Cortisol metabolism appears to be active soon after birth in guineapigs. Indeed, plasma cortisol half-life measured in three day-old animals resembles that of adult guinea-pigs (48 min). The metabolic clearance rate (MCR) of plasma cortisol as measured by continuous infusions of ³H-cortisol in fetal and newborn guinea-pigs remained very low, increasing slowly and regularly during the perinatal period without abrupt change at birth. Whole cortisol MCR in fetus is presented as the resultant of the concomitant actions of three factors: transfer to the mother, fetal irreversible removal rate and placental metabolism. True fetal cortisol MCR could be dissociated from total cortisol MCR measured in fetus by comparing the ratios of other measured parameters in maternal and fetal plasmas. Until ten days post partum, cortisol MCR varied independently of body weight growth and reflected the maturation of catabolizing hepatic enzymes.     

Consequences of acute stress and cortisol manipulation on the physiology, behavior, and reproductive outcome of female Pacific salmon on spawning grounds

Life-history theory predicts that stress responses should be muted to maximize reproductive fitness. Yet, the relationship between stress and reproduction for semelparous salmon is unusual because successfully spawning individuals have elevated plasma cortisol levels. To tease apart the effects of high baseline cortisol levels and stress-induced elevation of cortisol titers, we determined how varying degrees of cortisol elevation (i.e., acute and chronic) affected behavior, reproductive physiology, and reproductive success of adult female pink salmon (Oncorhynchus gorbuscha) relative to different states of ovulation (i.e., ripe and unripe). Exhaustive exercise and air exposure were applied as acute stressors to manipulate plasma cortisol in salmon either confined to a behavioral arena or free-swimming in a spawning channel. Cortisol (eliciting a cortisol elevation to levels similar to those in post-spawn female salmon) and metyrapone (a corticosteroid synthesis inhibitor) implants were also used to chemically manipulate plasma cortisol. Cortisol implants elevated plasma cortisol, and impaired reproductive success; cortisol-treated fish released fewer eggs and died sooner than fish in other treatment groups. In contrast, acute stressors elevated plasma cortisol and the metyrapone implant suppressed plasma cortisol, but neither treatment significantly altered reproductive success, behavior, or physiology. Our results suggest that acute stressors do not influence behavior or reproductive outcome when experienced upon arrival at spawning grounds. Thus, certain critical aspects of salmonid reproduction can become refractory to various stressful conditions on spawning grounds. However, there is a limit to the ability of these fish to tolerate elevated cortisol levels as revealed by experimental elevation of cortisol.     

Circadian variation in the CSF cortisol concentration of the rhesus monkey

Cortisol concentrations in the cerebrospinal fluid (CSF) of the rhesus monkey were found to undergo a marked diurnal variation. Hourly samples of CSF from 4 adult male rhesus monkeys showed a mean peak cortisol concentration of 1.56 ± .29 μg% occuring between 0800–0900 hrs and a mean minimum concentration between 2200-0000 hrs of 0.21 ± .06 μg%. The mean daily CSF cortisol concentration increase was 900%, a greater variation than has been reported for plasma cortisol diurnal changes.     

Effects of repeated stress during pregnancy in ewes on the behavioural and physiological responses to stressful events and birth weight of their offspring

Stressors are frequently encountered during the pregnancies of farm animals. However, very few studies have investigated the effects of repeated stress in pregnant females on their offspring. Forty-eight ewes at 2.5 months of pregnancy were selected for their high or low cortisol response to isolation. Half of the ewes were subjected, twice a week during the last 5 weeks of gestation, to isolation. The first isolation bout of each week consisted only of isolation from conspecifics, while the second bout of each week consisted of isolation in the presence of a dog. The cortisol responses of ewes were measured during the treatment. The other half of the ewes was drafted and released without further disturbance. The emotional reactivity of the lambs to a light contrast test, a startling stimulus test and a social isolation test were studied at 25 days of age. The lambs were retested at 8 months of age in the same tests and also in a novel arena and a novel object tests. Cardiac responses to the startling stimulus were studied at 8 months of age. Basal cortisol concentrations and cortisol response after the isolation test were studied at both ages and cortisol response to ACTH was studied at 25 days of age. Ewes repeatedly exposed to the treatment of isolation plus presence of a dog habituated to the treatment. Moreover, the initial differences between the high and low reactivity ewes were not apparent when the stress treatment was subsequently imposed. Lambs prenatally stressed were heavier at birth than control lambs. The prenatally stressed lambs showed more exploration and locomotion in the behavioural tests at 8 months of age but not at 25 days of age. At 25 days of age, the basal cortisol concentrations were higher in the prenatally stressed lambs compared to the control lambs. Whereas these results suggest that mild prenatal stress of lambs has no adverse effect on the behavioural and cortisol responses to a range of stressors, there is evidence that this treatment increases birth weight and exploratory behaviour of prenatally stressed lambs. Clearly these results require confirmation.     

Effects of adrenocorticotropin stimulation on cortisol dynamics of pregnant gilts and their fetuses: implications for prenatal stress studies

The effect of adrenocorticotropic hormone (ACTH) administration on plasma cortisol concentrations was determined in pregnant gilts and their fetuses. In a first experiment, 100 IU ACTH (Synacthen Depot) was administered intramuscularly to the gilts every second day from Days 49 to 75 of gestation. ACTH injections were carried out at 08:00 h and, thereafter, 10 blood samples were taken within the following 8h via jugular catheters. Blood samples were analysed for plasma cortisol concentrations, and results were compared with values from animals which were treated with physiological saline and untreated animals (blood sampling only). The values for plasma cortisol concentrations increased until 3h after ACTH applications to a mean maximum level of 276.5+/-17.2 nmol/l in the whole 4-week stimulation period. Plasma cortisol levels did not return to pre-treatment values within the 8 h post-injection. No differences in cortisol levels were found between the physiological saline and untreated control, and no habituation of the adrenocortical response to ACTH was found during the 4-week stimulation period. In a second experiment, 100 IU ACTH were administered to pregnant gilts at gestation Day 65. After 3 h, fetuses were recovered under general anaesthesia and blood samples were taken from the umbilical vein, artery, and, after decapitation, from periphery. Application of ACTH to the sows significantly increased their plasma cortisol concentrations (P<0.001), and also increased plasma cortisol concentrations in peripheral blood samples from the fetuses (P=0.09) and in the umbilical vein (P<0.001) and artery (P<0.01), respectively. Plasma ACTH concentrations did not differ in fetuses from ACTH-treated or control sows. The results show that in gilts the adrenocortical response to an exogenous application of Synacthen Depot is consistent over time during mid-gestation. Furthermore, cortisol but not ACTH levels were increased in fetuses from ACTH-treated sows, indicating that maternal cortisol can cross the placenta during mid-gestation. The stimulation of maternal cortisol release through exogenous ACTH with subsequent elevation of fetal cortisol levels is, therefore, a useful approach for studying effects of elevated maternal glucocorticoids in prenatal stress studies in pigs.