Effect of chronic stress in the blood pressure in the rat: ACTH administration

Sound and Vibration as Research Variables in Terrestrial Vertebrate Models

Sound and vibration have been shown to alter animal behavior and induce physiological changes as well as to cause effects at the cellular and molecular level. For these reasons, both environmental factors have a considerable potential to alter research outcomes when the outcome of the study is dependent on the animal existing in a normal or predictable biological state. Determining the specific levels of sound or vibration that will alter research is complex, as species will respond to different frequencies and have varying frequencies where they are most sensitive. In consideration of the potential of these factors to alter research, a thorough review of the literature and the conditions that likely exist in the research facility should occur specific to each research study. This review will summarize the fundamental physical properties of sound and vibration in relation to deriving maximal level standards, consider the sources of exposure, review the effects on animals, and discuss means by which the adverse effects of these factors can be mitigated.

Stress Response Simulated by Continuous Injection of ACTH Attenuates Lipopolysaccharide-Induced Inflammation in Porcine Adrenal Gland

On modern farms, animals are at high risk of bacterial invasion due to environmental stress factors. The adrenal gland is the terminal organ of the stress response. The crosstalk between adrenal endocrine stress and innate immune response is critical for the maintenance of immune homeostasis during inflammation. Thus, it's important to explore whether stresses play a pivotal role in lipopolysaccharide (LPS)-induced inflammatory response in the porcine adrenal gland. Thirty-days-old Duroc × Landrace × Large White crossbred piglets (12 ± 0.5 kg) were randomly allocated into four groups in a 2 × 2 factorial arrangement of treatments, including ACTH pretreatment (with or without ACTH injection) and LPS challenge (with or without LPS injection). Each group consisted of six male piglets. The results showed that our LPS preparation alone induced mRNA expressions of IL-1β, IL-6, TNF-α, IL-10, COX-2, TLR2, TLR4, and GR (P < 0.05). ACTH pretreatment downregulated the TLR2 mRNA and IL-6 protein level induced by our LPS preparation significantly (P < 0.05) by one-way ANOVA analysis. Treatment with LPS alone extremely significantly decreased ssc-miR-338 levels (P < 0.01). Interaction of ACTH × LPS was significant for cNOS level (P = 0.011) and ssc-miR-338 expression (P = 0.04) by two-way ANOVA analysis. The LPS treatment significantly downregulated cNOS levels (P < 0.01), which was significantly attenuated by ACTH pretreatment (P < 0.05). Lipopolysaccharide alone did not affect ssc-miR-146b expression levels compared to that in the vehicle group. However, ACTH pretreatment in combination with LPS significantly increased this micro-RNA expression (P < 0.05). TLRs 1–10 were all expressed in adrenal tissue. The LPS challenge alone induced remarkable compensatory mitochondrial damages at the ultrastructural level, which was alleviated by ACTH pretreatment. Accordingly, ACTH pretreatment was able to block LPS-induced secretion of local adrenal cortisol (P < 0.05). Taken together, our results demonstrate that ACTH pretreatment seems to attenuate LPS-induced mitochondria damage and inflammation that decreased cNOS activity in the adrenal gland and ultimately returned local adrenal cortisol to basal levels at 6 h post LPS injection.

Impacts of Subchronic, High-Level Noise Exposure on Sleep and Metabolic Parameters: A Juvenile Rodent Model

BACKGROUND

Noise is an environmental factor that has been associated with metabolic and sleep disorders. Sleep is a vital function, since it underpins physiologic processes and cognitive recovery and development. However, the effects of chronic noise exposure on the developing organism are still subject to debate.

OBJECTIVE

The objective of the present study was to assess the effects of subchronic, high-level noise exposure on sleep, apnea, and homeostasis in juvenile rats.

METHODS

Twenty-four 3-wk-old male Wistar rats were exposed to noise [[Formula: see text], [Formula: see text]] for 5 wk and 2 d during the 12-h rest period. Data on sleep stages, food and water intake, apnea, and body and organ weight were recorded.

RESULTS

Five weeks of high-level noise exposure were associated with hyperphagia ([Formula: see text]), body weight gain ([Formula: see text]), a heavier thymus ([Formula: see text]), and heavier adrenal glands ([Formula: see text]). A sleep analysis highlighted microstructural differences in the active period: in particular, the mean daily amount of rapid eye movement (REM) sleep as a proportion of total sleep time (TST) was higher. The mean daily amount of non-REM (NREM) sleep was lower in the exposed group, meaning that the intergroup difference in the TST was not significant. During a 1-h, noise-free plethysmographic recording during the rest period, the mean total amount of active wakefulness (AW) was lower in the exposed group (by 9.1 min), whereas the mean duration of an episode of REM sleep was higher (by 1.8 min), and the TST was higher (by 10.7 min).

DISCUSSION

Subchronic exposure of juvenile rats to high-intensity noise during the rest period was associated with some small but significant sleep disturbances, greater food and water intakes, greater body weight gain, and greater thymus and adrenal gland weights. The main effects of noise exposure on sleep were also observed in the 1-h plethysmography session after 5 wk of exposure. https://doi.org/10.1289/EHP4045.

MDMA (ecstasy) enhances loud noise-induced morphofunctional alterations in heart and adrenal gland

Noise is an environmental stressor increasingly more present in modern life and, in particular, in a variety of recreational contexts. The aim of this work is to show the effects of noise on the myocardium and adrenal gland, through a careful review of the literature dealing with the peripheral effects of noise exposure in experimental and clinical studies. Noise induces adverse effects in human health, principally involving the cardiovascular and autonomic nervous systems, and the endocrine apparatus. Several factors in recreational environments potentially worsen the effects induced by loud noise. Among these, the intake of 3,4-methylenedioxymethamphetamine (MDMA) is frequently associated with noise exposure in recreational situations, because of its high compliance within social and relaxation settings. For this reason, MDMA is defined as a club drug--as its intake by young people often occurs in association with other factors, such as aggregation, high temperatures, and noise. It is known that self-administration of MDMA by humans causes severe toxicity. In particular, the myocardium is affected early after MDMA intake--resulting in tachycardia, hypertension, and arrhythmia. Furthermore, MDMA alters the activity of the adrenal glands by elevating catecholamines and corticosterone levels. This review shows that combining MDMA and loud noise exposure potentiates the effects that are produced by each single stimulant alone as seen in experimental animal models. The convergence of the effects of prolonged loud noise exposure and the consumption of MDMA on the same system might explain the sudden fatal events that happen in recreational situations.

The effect of chronic variable stress on bowel habit and adrenal function in rats

BACKGROUND AND AIM

Increased colonic motility is a well-known stress response and corticotropin releasing hormone plays an important role in this response, but sequential change of bowel habit and adrenal function during chronic stress has not been reported. The objective of this study was to evaluate the effect of chronic stress on bowel habit and adrenal function.

METHODS

Male Sprague-Dawley rats were exposed to chronic variable stress (CVS) for 6 weeks. We measured daily the number and weight of pellets and weekly urinary corticosterone. After 6 weeks of experiment, visceromotor response (VMR) to colorectal distention (CRD), serum corticosterone and adrenal glands weight were measured.

RESULTS

The number and weight of pellets in CVS rats was greater than those of the control rats initially and decreased during the later period. However, CVS rats showed continuously exaggerated daily variation of pellet number than control rats to the end of experimental period. Urinary corticosterone was increased in CVS rat until the fifth week, but urine and serum corticosterone were not statistically different between groups at the sixth week. However, the relative weight of adrenal glands was higher in CVS rats at the sixth week. CVS rats showed exaggerated VMR to CRD than the control rats.

CONCLUSIONS

The prolonged and variable stress to rats induced sustained bowel habit dysfunction and visceral hypersensitivity without adaptation. Chronic stress also increased adrenal activity from the early phase and finally caused adrenal hypertrophy with relatively decreased activity. But adrenal change was not parallel to bowel habit change and it remains to be seen whether adrenal dysfunction is directly related to bowel habit dysfunction.

Species variability in cardiovascular research: the example of adrenocorticotrophin-induced hypertension

1. Lawrie Beilin has contributed greatly to international hypertension research through both animal and human studies. 2. Animals are used in biomedical research to gain insights that can be extrapolated ultimately to humans. 3. A simple experimental manipulation, adrenocorticotrophin (ACTH) administration, has a range of different cardiovascular effects in different species. 4. Caution should be exercised in extrapolating data from animals to humans.

Morphological alterations induced by loud noise in the myocardium: the role of benzodiazepine receptors

Noise represents an environmental stress factor affecting several organs and apparati, including the cardiovascular system. In experimental animals undergoing noise exposure, subcellular myocardial changes have been reported, especially at mitochondrial level; in particular, after 6 hours of exposure only the atrium exhibited significant mitochondrial alterations, whereas after 12 hours as well as subchronic exposure both atrium and ventricle were damaged. The first part of the present article overviews the experimental evidence on effects of noise on the myocardium. In the second part, the review analyzes the role of benzodiazepine receptors and the potential efficacy of benzodiazepine ligands in preventing the mitochondrial damage induced by noise exposure. Drugs acting at both central and peripheral benzodiazepine receptors significantly prevent this damage. Differences in the amount and the duration of the protective effect might depend on variability in the potency and pharmacokinetics of the specific drug. The effects of the combined treatment with selective and non-selective peripheral benzodiazepine ligands on noise stimulation are discussed at biochemical level reviewing studies on the effects of noise exposure on mitochondrial fractions.

Stressful animal housing conditions and their potential effect on sympathetic neurotransmission in mice

Although the sympathetic nervous system (SNS) plays a major role in mediating the peripheral stress response, due consideration is not usually given to the effects of prolonged stress on the SNS. The present study examined changes in neurotransmission in the SNS after exposure of mice (BALB/c) to stressful housing conditions. Focal extracellular recording of excitatory junction currents (EJCs) was used as a relative measure of neurotransmitter release from different regions of large surface areas of the mouse vas deferens. Mice were either group housed (control), isolation housed (social deprivation), group housed in a room containing rats (rat odor stress), or isolation housed in a room containing rats (concurrent stress). Social deprivation and concurrent stressors induced an increase of 30 and 335% in EJC amplitude, respectively. The success rate of recording EJCs from sets of varicosities in the concurrent stressor group was greater compared with all other groups. The present study has shown that some common animal housing conditions act as stressors and induce significant changes in sympathetic neurotransmission.

Housing and welfare in laboratory rats: effects of cage stocking density and behavioural predictors of welfare

Using male and female Alderley Park (Wistar-derived) rats housed in single-sex groups in standard laboratory cages, we looked at the effect of group size (one, three, five or eight) on competitive behaviour and time budgeting (initial and longer term), changes in their serum testosterone (males), corticosterone and antibody concentrations, and organ pathology at age 16 weeks, together with the interrelationships between behavioural measures and pathophysiological indices of social stress. Group size had only limited long-term effects on overall time budgeting and did not affect pathophysiological responses, although there were highly significant differences between individuals in replicate cage groups. Pathophysiology within both sexes showed strong and highly specific correlations with a small subset of behaviours suggesting frustrated attempts to escape from cages, including chewing the cage bars. Escape-related behaviour also correlated strongly with one component of competitive behaviour, Aggressive Grooming within both sexes, although Aggressive Grooming correlated with pathophysiological responses only among males. Females generally showed greater escape-related behaviour associated with greater signs of pathophysiology regardless of the level of aggression shown between cagemates. Major differences in intercorrelated behavioural and pathophysiological responses between replicate groups implied that the individual composition of groups rather than their size had the greater impact on the welfare of the rats, especially among females. This may be consistent with adaptive sex differences in their competitive reproductive strategies. The frequency of apparent escape-related behaviours and Aggressive Grooming, particularly when rats are first introduced into their cage groups, may provide a simple assessment of the welfare implications of particular cage groupings. Copyright 1999 The Association for the Study of Animal Behaviour.

Stress induced changes in transmitter release from sympathetic varicosities of the mouse vas deferens

Activation of the sympathetic nervous system is an important component of the response to stress, but the effects of prolonged stress on sympathetic neurotransmission have not been assessed. In the present study we have examined the effect of 3 to 10 days exposure to stress induced by frequent handling and sham injections on neurotransmitter release from sympathetic varicosities of the mouse vas deferens. DiOC2(5)-fluorescence was used to visualise the sympathetic varicosities so that extracellular electrodes could be placed over known numbers of varicosities to monitor transmitter release using electrophysiological techniques. The frequency of excitatory junction currents (EJCs) increased with increasing duration of exposure to stress. The mean and maximum EJC amplitude significantly increased by 107% and 43%, respectively after 10 days of exposure to stress. The density of sympathetic varicosities innervating smooth muscle of the mouse vas deferens was not changed throughout the duration of the exposure to stress. The findings from this study demonstrate that the efficacy of transmitter release from the sympathetic varicosities is altered by repeated exposure of mice to stressful stimuli, such as handling and sham injections. Since such procedures are routine in many pharmacological experiments, it is important that investigators are aware of these changes so that due consideration is given when interpreting the data obtained from animals treated in this way.

Adrenocorticotrophin dose-response relationships in the rat: haemodynamic, metabolic and hormonal effects

OBJECTIVE

To determine adrenocorticotrophin dose-response relationships for increase of blood pressure and metabolic parameters of the Sprague-Dawley rat.

METHODS

We injected 120 male Sprague-Dawley rats twice daily subcutaneously for 10 days with 0.5, 1, 5, 50, 100, 200 or 500 microg/kg synthetic adrenocorticotrophin per day (all n = 10) or subjected them to sham injection (0.9% NaCl; n = 50). Systolic blood pressure, 24 h food intake, water intake, urine volume and body weight were measured. Data from a further 45 rats treated with 500 microg/kg per day adrenocorticotrophin in previous studies were included in the blood pressure analyses. After we had killed these rats, their organ weights (kidney, heart, adrenal) and plasma electrolyte, adrenocorticotrophin and serum corticosterone concentrations were measured.

RESULTS

On the final day of treatment systolic blood pressure of sham-injection control rats was 123 +/- 1 mmHg (n = 50). Compared with sham treatment, a low dose of adrenocorticotrophin (1 microg/kg per day) increased systolic blood pressure from 122 +/- 1 to 130 +/- 2 mmHg (P < 0.001) without any metabolic effects, whereas a high dose of adrenocorticotrophin (500 microg/kg per day) increased systolic blood pressure from 121 +/- 1 to 150 +/- 2 mmHg (P < 0.001, n = 55) with increases in intake of water and urine volume (P < 0.001, n = 10) and a decrease in body weight (P < 0.001, n = 10). Plasma adrenocorticotrophin and serum corticosterone concentrations for the sham-injection control group were 162 +/- 12 pg/ml (36 +/- 3 pmol/l) and 376 +/- 18 ng/ml (1038 +/- 50 nmol/l), respectively. Plasma adrenocorticotrophin concentration was elevated by injections of 100 (P < 0.05), 200 (P < 0.01) and 500 microg/kg adrenocorticotrophin per day (P = 0.001). Serum corticosterone concentration was not significantly different from that of sham-injection rats with 0.5-5 microg/kg adrenocorticotrophin per day but was increased by injection of 50-500 microg/kg adrenocorticotrophin per day (P < 0.001).

CONCLUSIONS

These results define 1 microg/kg adrenocorticotrophin per day, administered subcutaneously, as the threshold dose for causing a rise in blood pressure in the rat Thus administration of adrenocorticotrophin increases systolic blood pressure at doses that induce minimal adrenocorticotrophin metabolic effects. Administration of a low dose of adrenocorticotrophin to the rat is a suitable model for stress-induced hypertension.

Chronic immobilization stress reduces sodium intake and renal excretion in rats

The influence of chronic exposure to immobilization (IMO) on sodium appetite as well as sodium and potassium renal excretion in adult male Wistar rats was studied. The animals were individually housed and all variables under observation were measured in metabolic cages the first, seventh, and thirteenth days once the experiment had started. Half of the rats had access to water, and the remainder of the rats had access to both water and saline solution (1.5% NaCl). IMO reduced the intake of saline solution. Renal water, sodium, and potassium excretion in those IMO rats having access to saline were lower than in control rats. The effects of IMO were very similar during all observation days; therefore no evidence of adaptation to repeated stress was found. The present data indicate the following: (i) IMO stress reduced sodium appetite, probably as a secondary effect to the deficit in sodium renal excretion; (ii) IMO caused antidiuresis and antikaliuresis, only in those rats taking saline solution; (iii) no adaptation to repeated IMO stress was found in any of the tested variables. The reduction of sodium appetite observed in stressed rats might be a homeostatic mechanism to maintain sodium balance after impairment of renal sodium excretion caused by stress.

Acute noise stress, ACTH administration, and blood pressure alteration

Two groups of male Wistar rats were submitted to a single noise exposure (2640 Hz, 30 W, 102 dB, 15 min) (St group) or to a single dose of ACTH (1.5 IU/100 g b.wt.) (Ac group), respectively. A control group of nontreated rats (Co group) was used. Blood pressure (BP) was measured using an indirect tail cuff method and corticosterone (B) levels were measured by specific RIA. Haematocrit (Hc) and blood pH values were also evaluated. Acute treatments of both noise exposure and ACTH administration produced corticosterone hypersecretion and blood pressure elevation, with lower haematocrit and higher blood pH values than those found in the Co group. No differences were found between St and Ac treatments.

Body weight gain, food intake and adrenal development in chronic noise stressed rats

Wistar chronic treated rats (30 days) were used to investigate the effect of hypothalamic-pituitary-adrenal activity on growth, food intake and adrenal development (weight and DNA content). The animals were submitted to noise stress, ACTH administration and dexamethasone suppression test. Noise stress decreased body weight gain and food intake. No adrenal hypertrophy was observed but an increase in relative DNA content by stress has been found. ACTH and dexamethasone treated rats showed a body weight and food intake decrease vs. controls. The effect on body weight was higher in dexamethasone treated rats. Adrenal hypertrophy and hyperplasia were found in ACTH treated rats, whereas dexamethasone provoked adrenal atrophy with a decrease in DNA content.