Consistency in catecholamine and cortisol excretion patterns over experimental conditions

Measures of adrenaline, noradrenaline and cortisol excretion and heart rate in five experimental conditions (three for heart rate) and three baseline conditions were obtained from 24 male and 24 female university students. For each sex group correlation coefficients between variables were calculated on the basis of (1) absolute measures, (2) absolute differences between experimental and baseline measures, and (3) experimental measures expressed as log percentages of baseline measures. For both sex groups and for the three types of data it was consistently found that adrenaline excretion correlated significantly and positively with noradrenaline, cortisol and urine excretion and that cortisol excretion correlated significantly with urine excretion. Furthermore, in females, absolute measures of noradrenaline were significantly positively correlated with heart rate.     

Methodological aspects on measurement of Clara cell protein in urine as a biomarker for airway toxicity, compared with serum levels

The Clara cell protein CC16, secreted from Clara cells in the lung, is discussed as a potential biomarker for toxic effects on the airways. An increased concentration of CC16 in serum may be caused by increased permeability of the lungs, caused by high levels of air pollution. Since CC16 is eliminated by renal excretion, it may be possible to use urine instead of serum samples. Few studies have been conducted on urinary CC16 (U-CC16), however.The aim was to investigate the optimal way of sampling and quantifying CC16 in urine samples and compare CC16 in human serum and urinary samples. Repeated sampling was performed in two groups of healthy subjects. First morning urine, 24 h urine, and matched blood and urine samples were collected.The excretion of U-CC16 increased over the day, e.g. from 0.08 microg h(-1) in the morning to 0.28 microg h(-1) in daytime and 0.16 microg h(-1) in the evening (medians in males). Morning samples (microg h(-1)) from males properly reflected the 24 h excretion (r = 0.91). The best correlation with 24 h excretion was obtained with creatinine-corrected first morning urine samples (r > 0.9). Generally, females had lower excretion of CC16 than males (medians 2.5 microg 24 h(-1) in females and 16 microg 24 h(-1) in males). There was significant intraindividual variation, but the interindividual variation was larger in both groups. There was an association between serum CC16 (S-CC16) and U-CC16 in morning samples. With optimal methods for sampling U-CC16, urine samples may be used in experimental studies of air pollution.     

Gender specific effects of a mild stressor on alcohol cue reactivity in heavy social drinkers

RATIONALE: Stress plays an important role in the development and maintenance of alcohol-abuse. Some of the effects of stress on alcohol-related behaviours, however, appear to be gender-dependent. AIM: The present study set out to examine the effects of stress on feelings of desire for alcohol, skin conductance response and alcohol consumption in the presence of alcohol-related cues in relation to gender. Participants were heavy non-dependent alcohol drinkers. METHODS: Thirty-two (16 males) participants drinking more than 21 units of alcohol per week were randomly allocated to undergo the experimental stress (based on the 'Trier Social Stress' Test) or the non-stress procedure before the alcohol cue exposure procedure, during which participants handled and smelled their preferred drink. Mood and saliva cortisol level changes were used as indices of the stress effects, while alcohol craving, skin conductance and alcohol consumption were the cue reactivity measures. RESULTS: Self ratings of anxiety and tension increased and cortisol levels remained high in the stress compared to the non-stress condition; no gender differences were found. Stress induced gender-specific effects with regard to skin conductance response and alcohol consumption measurements. Stressed females did not show an increase from baseline in the skin conductance response during the alcohol cue-exposure session, which was observed in the non-stressed females; they also consumed less alcohol than males under stress. CONCLUSION: Female participants respond less to alcohol-related cues when in a negative mood state. Such a finding suggests that females when in a negative mood may be less sensitive to positive incentive processes mediating cue reactivity compared to males.     

Increased cortisol levels in cognitively challenging situations are beneficial in young but not older subjects

Rationale  Adaptation to stressful situations changes with increasing age. This is also reflected in age-related differences in effects of acute stress on, e.g., episodic memory. Less is known about age-related differences of the cognitive effects of individual stress responses to challenging situations. Objective  To investigate the influence of the individual cortisol response (as a marker for the individual stress level) on behavioral and neural measures during a challenging memory paradigm. Materials and methods  Twenty young and 12 older subjects were scanned using functional magnetic resonance imaging during encoding and retrieval of spatial contextual information. Salivary cortisol levels were measured before and after scanning. Results  A multiple regression analysis of behavioral data showed an interaction effect of age and cortisol response on memory for the items and their spatial context during retrieval due to increased accuracy with increasing cortisol responses in young compared to old subjects. During encoding, this was reflected in a positive effect of the cortisol response on prefrontal activity in young but not in older subjects. During retrieval, there was a negative effect of the cortisol response on brain activity in the hippocampus and prefrontal regions in older but not in young subjects. Conclusions  The data suggest an increased efficiency to encode items and their context with increasing cortisol responses in young subjects, and a decreased efficiency to retrieve information with increasing cortisol responses in older subjects. We conclude that neuroendocrine responses are differentially associated with behavioral and neural measures in cognitively challenging situations in young and older volunteers. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Psychosocial environment and health: methodological variability of the salivary cortisol measurements

Salivary cortisol offers a novel approach to understand the relationship between psychosocial environment and health. This study examines the intra-individual relationships among indicators of the cortisol circadian rhythm and investigates the influence of determinants affecting the day-to-day variability of the cortisol measures. Over three weekdays, 87 healthy subjects (63 females and 24 males) collected saliva samples at seven time points to assess the cortisol awakening response (CAR), and to evaluate the post morning cortisol profile. The generalized estimating equations method was used to explore the relations between repeated cortisol measures and potential determinants (sociodemographic, health, and sampling factors) influencing salivary cortisol levels. Younger age, being smoker, and sampling on a working day were associated with higher at awakening and total cortisol excretion in the morning period. Higher overall cortisol excretion and cortisol increase in the first hour of the day were found for adherents to sampling procedure. Higher educational level was found associated with greater total cortisol excretion in the morning and post morning period, while a flatter diurnal slope was found in smokers. Results are consistent with the knowledge that the circadian cortisol rhythm is differentially determined by situational factors and that results obtained in the early morning hour are of crucial importance corroborating the evidence that the CAR is a highly state-dependent phenomenon. These data indicate that many confounding factors need to be controlled when using salivary cortisol as biomarker of the mind-health interrelationship.     

On the urinary output of vasopressin,epinephrine and norepinephrine during different stress situations

The urinary excretion of vasopressin, epinephrine and norepinephrine was studied in normal subjects before and during three stress situations, viz. a performance test (consisting of mental arithmetic, the Stroop colour-word test, delayed auditory feedback and hand steadiness), the application of cold and the production of ischaemic muscle pain. The heart frequency, the systolic and diastolic blood pressure and the urine volume were measured as well.During the performance test the vasopressin, epinephrine and norepinephrine excretion increased significantly. During the application of cold only norepinephrine excretion increased significantly. During the production of muscle pain the vasopressin and epinephrine excretion increased significantly, the norepinephrine excretion rose, but not significantly. The systolic and diastolic blood pressure showed a significant increase during these three stress situations. The significant increase in heart rate was less pronounced during the cold and pain stress than during the performance stress. The urine volume was not significantly changed during the stress situations.These results were discussed in relation to the emotional arousal level during the performance test on one side and to the unpleasant but familiar conditions during the application of cold and the production of pain on the other side.     

Comparison of neuroendocrine measurements under laboratory and naturalistic conditions

Urinary catecholamines and cortisol were measured in healthy nonsmoking white collar workers (14 male and 15 female managers, 15 male and 14 female clerical workers), aged 30-50 years, during a one-hour period of laboratory-induced stress comprising five tests and a Type A interview, and during a subsequent period of rest in the laboratory. Values were compared with data obtained four months earlier from the same subjects during a normal day at work (4 values) and during a work-free day at home (4 values). No significant group differences were found during rest in the laboratory. However, during laboratory-induced stress, female managers had the highest norepinephrine values, which contributed to significantly (p less than 0.01) higher values in women than in men. Correlations between absolute measurements from laboratory and naturalistic conditions were generally positive and reached significance in most cases. Correlations between reactivity measurements in the laboratory and at work (change from rest to stress and from home to work, respectively) were generally low, whereas correlations between reactivity at different times of the day were relatively high. The data suggest that generalizability of neuroendocrine reactivity from laboratory stress to real-life stress is low. However, in agreement with earlier experimental findings, absolute levels of catecholamine and cortisol excretion were consistent over conditions and time.     

Stimulation by oestradiol of the urinary excretion of perfluorooctanoic acid in the male rat

The urinary excretion of perfluorooctanoic acid (PFOA) was studied in male Wistar rats after castration and oestradiol administration as well as in intact females and males. During the first 24 hr females excreted 72 +/- 5% (N = 6) of a single intraperitoneal dose of PFOA (50 mg/kg) in urine whereas the intact males excreted only 9 +/- 4% (N = 6). After castration followed by oestradiol administration (500 micrograms/kg every 2nd day for 14 days), the males excreted PFOA in urine in similar amounts as the females (68 +/- 14% at 24 hr, N = 10). Oestradiol treatment of non-castrated males produced similar results (61 +/- 19% at 24 hr, N = 10). Also castration without oestradiol administration significantly enhanced the renal PFOA excretion, but not as effectively as oestradiol treatment. After 96 hr, the concentration of PFOA in serum of intact males was 17-40 times higher than in the serum of other groups. PFOA was similarly bound by the proteins in the serum of females and males. Phase II metabolism of PFOA was not shown either in males or females.     

Sex and age differences in mercury distribution and excretion in methylmercury-administered mice

Sex differences in mercury distribution and excretion after single administration of methylmercury chloride (MMC, 5 mg/kg) were studied in mice. A sex difference in urinary mercury excretion was found in sexually mature mice (age of 7 wk) of C57BL/6N and BALB/cA strains. Males showed higher mercury levels in urine than females, though no significant difference was found in fecal mercury levels 24 h post exposure to MMC. The higher urinary excretion rates in males accounted for significant lowering of mercury levels in the brain, liver, and blood, but not in the kidney, which showed higher values. At 5 min, however, these sex difference was found only in the kidney, showing higher levels in males. Changes in mercury distribution with time were studied in C57BL/6N mice. The brain mercury increased in both sexes up to 3 d, and decreased only in males on d 5. Liver and blood mercury decreased with time in both sexes, and these were constantly higher in females than in males. Renal mercury in males decreased to similar levels to females on d 3. The sex differences at various ages were studied with C57BL/6N mice 24 h after dosing. Two-week-old mice, the youngest in this study, did not show significant sex difference in the mercury distribution and excretion, and their urinary mercury levels were much lower as compared to the older mice. Then, urinary mercury excretion in both sexes increased at 4 wk of age and then decreased at 45 wk of age. At 4, 7, 10, and 45 wk of age, males showed higher urinary mercury levels than females. These studies demonstrated sex and age differences in the mercury distribution and urinary excretion after methylmercury administration in mice. From these findings, it has been suggested that urinary mercury excretion may be related to sex hormones, especially androgens.     

Sex differences in the metabolism of hexachlorobenzene by rats and the development of porphyria in females

Male and female F 344 rats were dosed every other day for 103 days with 50 μmole of hexachlorobenzene (HCB)/kg. Females developed a hepatic porphyria, the urine and liver levels of porphyrins being 40- and 310-fold high respectively than those of males. Urine was periodically hydrolysed and analysed for the three metabolites pentachlorophenol, 2,3,5,6-tetrachlorobenzene-1,4-diol and pentachlorothiophenol (derived from the mercapturate). The combined urinary excretion of these was greater in females than males, especially during the first 10 weeks. Pentachlorthiophenol was particularly high in female urine. After 103 days this metabolite was slightly less in female faeces than in male's but free hepatic pentachlorothiophenol was 3.6-fold greater. Although total 24 hr excretions of metabolites were higher by females than males and after 7 daily doses of HCB, a difference in this respect was not conclusively proven. However, total pentachlorothiophenol excretion was always significantly greater by females. The male/female ratios for pentachlorophenol and pentachlorothiophenol in bile were identical to those for faeces. Excretion of metabolites by both adult males and females was stimulated by pretreatment with diethylstilboestrol (DES). No sex differences in metabolism were observed with immature rats.     

Physiological predictors of reproductive outcome and mother-infant behaviors in captive rhesus macaque females (Macaca mulatta).

Previous research has shown that offspring of females with low cerebrospinal fluid (CSF) 5-hydroxyindoleacetic acid (5-HIAA) concentrations are less likely to survive the first year of life than are offspring of females with high CSF 5-HIAA concentrations. In addition, studies of free-ranging rhesus macaque males have suggested that individuals with low CSF 5-HIAA concentrations suffer reduced reproductive success relative to their high serotonin counterparts. We examined CSF concentrations of the monoamine metabolites 5-HIAA and homovanillic acid (HVA), and plasma cortisol concentrations as predictors of first-time adult reproductive potential, maternal behavior, and overall social interactions in two groups of captive female rhesus macaques and their first offspring. Repeated CSF and blood samples were obtained from adult females in two social groups, and focal observations were performed for both new mothers and infants during the first month following parturition. We found that the reproductively aged nulliparous females who failed to give birth to their first offspring showed significantly lower CSF 5-HIAA concentrations than those females who gave birth. Among those females that gave birth to offspring, females with low CSF 5-HIAA concentrations and females with high plasma cortisol concentrations were overly protective and restrictive with their infants. CSF HVA concentration was not associated with reproductive output, social behavior, aggression, or mother-infant interactions in this sample of rhesus macaque females. We conclude that low CNS serotonin activity and high stress, measured by high plasma cortisol, are correlated with reduced reproductive success and patterns of high maternal restrictiveness in young adult female rhesus macaques.     

Circadian rhythms of paracetamol metabolism in healthy subjects; a preliminary report

Paracetamol was used as a "probe" drug to study the circadian rhythms of metabolite ratios in man. Paracetamol was orally administered to six volunteers at different times of day, 0-8 h and 8-24 h urine samples being measured for sulphate and glucuronide formation. Results showed a wide interindividual variation in paracetamol metabolite excretion among the six subjects. However, when a 500 mg dose was administered, free paracetamol excretion was minimal when the dose was given at 12.00 h and maximal when given at 20.00 h for the 0-8 h collection period. Sulphate excretion rose slightly at night and decreased gradually during the day. Glucuronide excretion was greatest with drug administration at 16.00 h and least if paracetamol was ingested at 08.00 h. The 8-24 h profiles were roughly similar. At a higher dose (1500 mg), free paracetamol excretion showed a minimum from dosing at 20.00 h and a maximum from dosing at 24.00 h in both 0-8 h and 8-24 h collections, while the sulphate conjugate peaked for doses at 20.00 h and 8.00 h with collections at 0-8 h and 8-24 h respectively. The glucuronide conjugate was maximal for paracetamol administration at 16.00 h for both 0-8 h and 8-24 h collections. There appears to be a 12 hour phase variation in excretion; this may result from circadian rhythms in absorption and enzyme activities. These parameters may also affect metabolism at higher dose levels, so that the hepatotoxicity of paracetamol could vary with the time of dose.     

Altered levels of sex and stress steroid hormones assessed daily over a 28-day cycle in early abstinent cocaine-dependent females

Rationale There is growing evidence of alterations in brain stress and reward circuits associated with cocaine dependence. Sex differences are also documented and sex steroid hormones have been linked to cocaine reinforcement. Objectives The current study therefore assessed daily fluctuations in stress and sex hormones in cocaine-dependent females compared with healthy females. Method Daily salivary samples of cortisol, progesterone, and estradiol were collected at waking across 28 days from 12 cocaine-dependent females receiving inpatient treatment and 10 healthy females. Participants also completed mood-rating scales each week corresponding to four phases of the menstrual cycle and cocaine craving was monitored in cocaine patients at each phase. Results Cocaine-dependent females in their first month of abstinence demonstrated significantly higher levels of both cortisol and progesterone across the menstrual cycle and significantly lower estradiol/progesterone (E2/P) ratios compared to healthy controls. They also showed significantly increased negative mood compared with controls, but no variation in cocaine craving across the menstrual cycle. Conclusions Findings indicate altered stress and sex hormones suggestive of an overactive stress system during the first month of cocaine abstinence after chronic cocaine abuse. These increased levels of cortisol and progesterone could impact both abstinence-related symptoms such as negative mood and susceptibility to drug-seeking behavior in cocaine-dependent females.     

Anger,anxiety, and depressive affect as predictors of stress-induced cortisol production in khat and tobacco users

IntroductionGlucocorticoid activity is disrupted in substance users including khat chewers who also use tobacco. Anger, dysphoria, and anxiety can mediate this relationship. The aim of this study was to contrast emotion dysregulation and substance use variables as predictors of post-stress cortisol output.Materials and methodsComparable numbers of males (n = 90) and females (n = 85) including controls, khat only, and concurrent khat and tobacco users participated in a stress study. Depressive affect, anxiety, anger, substance use patterns, and saliva samples were collected following a standardized laboratory stress manipulation.ResultsRegression analysis showed that high depression and low anxiety was associated with high post-stress cortisol, but only in co-users of tobacco and khat. Males, but not females, showed a significant association between co-use of khat and tobacco and cortisol, which appears to be mediated by frequency of use. The link between anxiety and post-stress cortisol in the co-users remained significant after controlling for nicotine dependence and substance use frequency.ConclusionAnxiety predicted the neuroendocrine consequences of concurrent use of tobacco and khat above and beyond sex, nicotine dependence, anger, and substance use frequency. Sex differences, however, are related to differences in nicotine dependence.     

Effect of metoprolol on 24-hour urinary excretion of adrenal steroids and kallikrein in patients with essential hypertension.

Treatment of fifteen patients with essential hypertension over four weeks using the beta 1-adrenoceptor blocking agent, metoprolol, resulted in a decrease in 24 h urinary excretion of kallikrein and aldosterone along with a decrease in plasma renin activity. There was no significant change in 24 h excretion rates of the free adrenal steroids deoxycorticosterone, 18-OH-deoxycorticosterone, corticosterone, cortisol or 18-OH-corticosterone during treatment, which were not significantly different from excretion rates of normal males, thus excluding inhibitory effects of adrenal steroids on urinary kallikrein activity. A positive correlation was found between plasma renin activity and urinary excretion of kallikrein during the control period and after 2 weeks on metoprolol, supporting the assumption of a preserved link between the renin-angiotensin-aldosterone system and the renal excretion of kallikrein in these patients. The decrease in kallikrein excretion during beta 1-adrenoceptor blockade in patients with essential hypertension may be explained by a reduction in sympathetic tone and by reduced activity of the renin-aldosterone system.     

Effect of acute environmental heat stress on urinary water and electrolyte excretion in the rat

Plasma cortisol and urinary excretion of water, sodium, potassium, calcium and magnesium have been studied in the rat after application of heat stress. There was a significant increase in plasma cortisol level after exposure to heat. During heat stress complete cessation of urine formation was observed. In the next 30 min there was statistically significant increase in the urinary excretion of water, sodium and calcium but not of potassium and magnesium. Urinary calcium/magnesium ratio was also significantly elevated. The increase in urinary water and electrolyte excretion seemed to be mediated through prostaglandins since it could be abolished by administration of indomethacin prior to the application of heat stress. On the basis of these results, the possible role of heat stress in the genesis of urolithiasis has been discussed.     

Acute stress impairs spatial memory in male but not female rats: influence of estrous cycle

We investigated how sex and estrous cycle influenced spatial recognition memory in the Y-maze after exposure to acute restraint stress. In Experiment 1, intact male and female rats were restrained for 1 h and then 2 h after the start of restraint, rats were trained on the Y-maze. After a 4 h delay, hippocampal-dependent spatial recognition memory was assessed. Acute stress produced opposite patterns between the sexes with spatial memory being impaired in males and facilitated in females. Serum corticosterone measures indicated that both sexes showed a robust corticosterone response after restraint and a moderate corticosterone response after Y-maze exposure. Serum corticosterone levels in response to restraint and Y-maze were not statistically different between the sexes. Experiment 2 examined the influence of the estrous cycle on spatial memory ability after acute stress. Acute stress facilitated spatial memory in females compared to controls, regardless of the estrous cycle phase (estrus and proestrus). Moreover, females in proestrus showed higher serum corticosterone levels during restraint compared to females in estrus. No differences in corticosterone levels were observed at baseline or following 2 h of recovery from restraint. These data show important differences in how sex and estrous cycle influence cognitive functions following acute stress.     

Absorption, distribution, metabolism and excretion of the cholecystokinin-1 antagonist dexloxiglumide in the rat.

Single oral doses of 14C-dexloxiglumide were rapidly and extensively absorbed in rats, and eliminated more slowly by females than by males. The respective half-lives were about 4.9 and 2.1 h. Following single intravenous doses, dexloxiglumide was characterised as a drug having a low clearance (6.01 and about 1.96 ml/min/kg in males and females respectively), a moderate volume of distribution (Vss, 0.98 and about 1.1 L/kg in males and females respectively) and a high systemic availability. It was extensively bound to plasma proteins (97%). Dexloxiglumide is mainly cleared by the liver. Its renal clearance was minor. In only the liver and gastrointestinal tract, were concentrations of 14C generally greater than those in plasma. Peak 14C concentrations generally occurred at 1-2 h in males and at 2-4 h in females. Tissue 14C concentrations then declined by severalfold during 24 h although still present in most tissues at 24 h but only in a few tissues (such as the liver and gastrointestinal tract) at 168 h. Decline of 14C was less rapid in the tissues of females than in those of males. Single intravenous or oral doses were mainly excreted in the faeces (87-92%), mostly during 24 h and more slowly from females than from males. Urines contained less than 11% dose. Mean recoveries during 7 days when 14C was not detectable in the carcass except in one female rat ranged between 93-101%. Biliary excretion of 14C was prominent (84-91% dose during 24 h) in the disposition of 14C which was also subjected to facile enterohepatic circulation (74% dose). Metabolite profiles in plasma and selected tissues differed. In the former, unchanged dexloxiglumide was the major component whereas in the latter, a polar component was dominant. Urine, bile and faeces contained several 14C-components amongst which unchanged dexloxiglumide was the most important (eg. up to 63% dose in bile). LC-MS/MS showed that dexloxiglumide was metabolised mainly by hydroxylation in the N-(3-methoxypropyl)pentyl sidechain and by O-demethylation followed by subsequent oxidation of the resulting alcohol to a carboxylic acid.     

Seasonal and sex influences on ketamine-induced analgesia and catalepsy in the rat; a possible role for melatonin

Data from this laboratory on ketamine-induced analgesia and catalepsy in rats revealed that factors other than dose modified the difference in the latency of the tail flick response (TFLD), a measure of analgesia, and the duration of the loss of the righting reflex (DLRR), a measure of catalepsy. Untreated female rats showed a longer latency than males in their response to a noxious stimulus at midnight, but not at noon. Females also showed a longer loss of righting reflex response to ketamine than did males, whether at noon or midnight; the loss of righting reflex at night was augmented in both. Although females showed analgesia with administration of ketamine at doses smaller than those which induced catatonia, males showed no analgesia without catatonia and comparable loss of the righting reflex occurred at doses much larger than for females. There was a 3-fold increase in the latency of the tail flick response and loss of righting reflex during the winter, as compared with summer, for females treated with ketamine; males showed a similar variation in the loss of righting reflex. Since analgesia is produced by both melatonin and ketamine, and since ketamine appears to share opiate receptors with an endogenous ligand, beta-endorphin, a role was sought for the pineal and melatonin in the variation of responsiveness to ketamine. Pinealectomized rats failed to show augmentation of the loss of righting reflex induced by ketamine at night and mice showed a seasonal variation in the analgesia induced by melatonin.(ABSTRACT TRUNCATED AT 250 WORDS)     

Post-operative corticosterone levels in plasma and feces of mice subjected to permanent catheterization and automated blood sampling

This study investigated the effects of surgical placement of permanent arterial catheters on plasma corticosterone levels, fecal corticosterone excretion and body weight in male BALB/c/Sca mice. In addition, the effects of voluntarily ingested buprenorphine in doses of 0.5 and 1.0 mg/kg body weight on these parameters were studied. A catheter was placed in the carotid artery during isoflurane anesthesia. Immediately after surgery, the mice were connected to an AccuSampler? μ and blood samples for plasma corticosterone quantification were collected automatically during the first 24 h postoperatively. All fecal boli produced 24 h before and 24 h after surgery were collected for fecal corticosterone excretion measures and the pre- and post-operative body weights were registered. Plasma corticosterone levels were in the range of 150-300 ng/ml after the surgical procedure and the body weight was significantly lower 24 h after surgery compared to its pre-operative value. Contrary to what was expected, the total fecal corticosterone excretion was significantly reduced 24 h after surgery, as was the defecation. Buprenorphine treatment significantly lowered the plasma corticosterone levels, but had no effect on fecal corticosterone excretion or body weight change. It was concluded that surgical placement of an arterial catheter induces a significant stress response, as judged by its effect on plasma corticosterone and body weight. Voluntary ingestion of buprenorphine improved postoperative recovery by lowering plasma corticosterone concentrations. Neither fecal corticosterone excretion nor body weight change seems suitable for postoperative stress assessment in mice in the present experimental setup.