Corticosterone Concentrations Research Articles

Corticosterone predicts double-brooding in female savannah sparrows (Passerculus sandwichensis).

Given that double-brooding (rearing two broods within a season) can increase annual fecundity, it is unclear why some females in multi-brooded populations rear only one brood per season. The Quality Hypothesis proposes that double-brooded females are high quality and, thus, have sufficient energetic resources available to bear the costs of rearing two broods per season. Glucocorticoids - endocrine hormones that have a critical role in energy regulation - could reflect female quality, and, therefore, also have the potential to indicate whether a female will rear a second brood. Using 12years of reproductive data on migratory Savannah sparrows (Passerculus sandwichensis) from a population in eastern Canada, we explored whether baseline corticosterone concentrations were correlated with measures of female quality (body condition and fat score) and whether a female's baseline corticosterone concentrations during her first brood would predict whether she attempted a second. We found weak evidence that baseline corticosterone was negatively correlated with female body condition and found strong evidence that baseline corticosterone was negatively correlated with fat score. There was weak evidence for a positive relationship between double-brooding and baseline corticosterone in females sampled during the first brood incubation stage. Additionally, there was moderate evidence to suggest that the probability of double-brooding was negatively related to baseline corticosterone in females sampled during the first brood nestling stage. Our results provide evidence that corticosterone can reflect female condition in the context of double-brooding and demonstrate the importance of considering breeding stage when assessing corticosterone concentrations in parents.

Social isolation during pregnancy disrupts maternal behavior and hippocampal neurochemistry in rats: A role for BDNF, corticosterone, and GABAARα1.

This study aimed to investigate the effects of social isolation stress during pregnancy on maternal behavior and associated neurochemical changes in the hippocampus of rats. Twenty female Sprague-Dawley rats were randomly assigned to either a group housing (two rats per cage: control group) or a social isolation stress group (one rat per cage: SI group) during pregnancy. At the end of the study, we assessed the levels of BDNF, corticosterone, and GABAARα1 in the hippocampus of the maternal brain, along with evaluating the endurance, integration, and emotional aspects of maternal behavior. Results indicated that social isolation stress significantly decreased maternal endurance, integration, and emotionality (self-calming) of maternal behavior. Concurrently, blood and the hippocampal corticosterone concentration significantly increased, while BDNF concentration significantly decreased in the SI stress group compared to controls. Moreover, GABAARα1 mRNA expression was significantly decreased in the hippocampus of socially isolated rats. These findings demonstrate that social isolation stress during pregnancy profoundly impacts maternal behaviors in rats, including endurance, integration, and self-soothing. The altered concentration of corticosterone and BDNF, and GABAARα1 mRNA expression in the hippocampus of social isolation group suggests disruptions in stress response regulation and synaptic plasticity during pregnancy to form normal maternal behavior.

Catecholamine synthesis and secretion by adrenal chromaffin cells is reduced in deer mice native to high altitude.

Hypoxia at high altitude can constrain aerobic metabolism and elicit physiological responses that are detrimental to health and fitness. Responses of the sympathoadrenal system are vital for coping with acute hypoxia, but can become maladaptive with prolonged activation in chronic hypoxia. We examined how adrenal function is altered in high-altitude populations of deer mice (Peromyscus maniculatus), which have evolved to overcome chronic hypoxia in their native environment. High- and low-altitude populations were each born and raised in common lab conditions, and then acclimated to normoxia or chronic hypoxia during adulthood. High-altitude mice exhibited lower plasma epinephrine concentrations than low-altitude mice in both normoxia and hypoxia. Primary cultures of chromaffin cells were used to examine the cellular mechanisms underlying differences in epinephrine secretion from the adrenal medulla. Chromaffin cells from high-altitude mice did not mount a diminished Ca2+ response to nicotinic stimulation, but cellular catecholamine stores were much lower in high-altitude mice than in low-altitude mice. Histological analyses of the adrenal gland showed that high-altitude mice did not have smaller adrenal medullae. Therefore, reductions in chromaffin cell catecholamine stores were the primary mechanism for lower secretion rates and circulating concentrations of catecholamines in high-altitude mice, which may help avoid sympathoadrenal over-activity in chronic hypoxia. Further exploratory analysis found that high-altitude mice have a larger adrenal cortex and higher plasma concentrations of corticosterone, which could reflect changes in stress responsiveness or metabolic regulation. Therefore, multiple evolved changes in the physiology of the adrenal gland may contribute to high-altitude adaptation in deer mice.

Effects of Urbanization on Ventral Patch Size and Phenotypic Correlates of Patch Expression in Male Western Fence Lizards (Sceloporus occidentalis).

In some animals, males use colorful ornaments or badges to visually communicate with conspecifics. These traits can be condition-dependent, suggesting that environmental changes could impact the intensity of male sexual signals. Drastic habitat changes caused by urbanization can act as physiological stressors, potentially affecting male signaling traits through changes to condition or immune function. Here, we quantified the effects of urbanization on ventral patch size and correlates of patch expression, namely body size, body condition, corticosterone concentrations, and ectoparasites in male Western Fence Lizards (Sceloporus occidentalis). We compared three aspects of male ventral color patches between urban and natural populations: area of the throat patch, total area of the paired belly patches, and total area of the black borders of the belly patches. All three area measurements across both habitat types were positively related to body size, and total belly patch area was positively related to body condition, indicating that these traits may signal male competitive ability and/or quality. Males from urban populations had larger throat patches than those from natural populations after controlling for body size. This difference in patch size was associated with a difference in probability of ectoparasite infection, but not with differences in corticosterone concentrations or body condition between urban and natural populations. Our results may indicate an effect of urbanization on immune function affecting male patch expression, although this idea remains untested. Overall, we show that urbanization can impact male sexual traits, which may have repercussions for visual communication in urban environments.

Analysis of the Reliability of Feather Sections for Corticosterone Measurement in Pekin Ducks.

The aim of this study was to identify the feather section, among the whole feather, rachis, and vane, with the highest reliability for corticosterone measurement in 10 Pekin ducks aged 42 days. In total, 60 samples (i.e., 20 per section) were collected and each section was analyzed in duplicate. Corticosterone levels were measured using ELISA and statistical analyses were performed using ANOVA in SAS 9.2, and the intra-class correlation coefficient (ICC) was tested using IBM SPSS. The level in the whole feather (12.55 ± 4.41 pg/mg) was significantly lower (p < 0.001) than that in the rachis (18.12 ± 5.70 pg/mg). No significant differences were observed between the rachis and the vane (20.40 ± 3.04 pg/mg). ANOVA results confirmed substantial hormonal variability depending on the feather part analyzed. The ICCs for the whole feather, rachis, and vane were 0.923, 0.876, and 0.004, respectively. The vane section exhibited the highest concentration and lowest variance, whereas the whole feather exhibited the highest ICC. Although the whole feather had the lowest concentration, it exhibited greater consistency. Further research is necessary to improve the feather corticosterone analysis method for more accurate analysis. In conclusion, the whole feather provides the most reliable measure of corticosterone concentration among the three parts.

Preceding sevoflurane inhalation in rats reduces the stress of intraperitoneal injection both in inexperienced experimenters and subject rats.

In this study, we found that sevoflurane inhalation in rats prior to intraperitoneal injection decreased stress in both inexperienced experimenters and subject rats. Inexperienced experimenters anaesthetised male Sprague Dawley rats by intraperitoneal injection of anaesthetics, with or without preceding sevoflurane inhalation. Analysis using a visual analogue scale indicated that participating experimenters felt less stress when they performed intraperitoneal injections on rats after subjecting them to sevoflurane inhalation than when performing intraperitoneal injections alone. Plasma corticosterone concentrations of the anaesthetised subject rats were lower when the intraperitoneal injection was preceded by sevoflurane inhalation. Thus, our results demonstrated that it is advisable for inexperienced experimenters, until they gain confidence with experience, to perform sevoflurane inhalation on male rats before intraperitoneal injections.

Day Late, Dollar Short: Runts of Asynchronously Hatched Songbird Broods Have Reduced Survival, Body Size, and Persistent Energy Deficits.

Many songbirds begin active incubation after laying their penultimate egg, resulting in synchronous hatching of the clutch except for a last-hatched individual ("runt") that hatches with a size deficit and competitive disadvantage to siblings when begging for food. However, climate change may elevate temperatures and cause environmental incubation as eggs are laid, resulting in asynchronous hatching and larger size hierarchies among siblings. Although previous work demonstrated that asynchronous hatching reduces nestling growth and survival relative to synchrony, the physiological mechanisms underlying these effects are unclear. To test the effects of asynchronous hatching on runt growth, survival, physiology, and compensatory growth-related tradeoffs, we manipulated incubation temperature in nest boxes of European starlings (Sturnus vulgaris) to increase asynchronous hatching and collected nestling morphological measurements and blood samples to assess physiology and development. Independent of heating treatment, runts from asynchronously hatched nests had lower survival than runts from more synchronous nests. Surviving runts from asynchronous nests were smaller and had reduced stress-induced corticosterone concentrations and reduced circulating glucose compared with runts from synchronous nests. Despite persistent size and energy deficits, runts from asynchronous nests did not have significant deficits in immunity or telomere length when compared with runts from synchronous nests, suggesting no trade-off between investment in immune development or telomere maintenance with growth. Overall, these results suggest that increased asynchrony due to climate change could reduce clutch survival for altricial songbirds, especially for the smallest chicks in a clutch, and that the negative effects of asynchrony may be driven by persistent energetic deficits.

Chronic stress induces behavioural changes through increased kynurenic acid by downregulation of kynurenine-3-monooxygenase with microglial decline.

Alterations in tryptophan-kynurenine (TRP-KYN) pathway are implicated in major depressive disorder (MDD). α7 nicotinic acetylcholine (α7nACh) receptor regulates the hypothalamic-pituitary-adrenal (HPA) axis. We have shown that deficiency of kynurenine 3-monooxygenase (KMO) induces depression-like behaviour via kynurenic acid (KYNA; α7nACh antagonist). In this study, we investigated the involvement of the TRP-KYN pathway in stress-induced behavioural changes and the regulation of the HPA axis. Mice were exposed to chronic unpredictable mild stress (CUMS) and subjected to behavioural tests. We measured TRP-KYN metabolites and the expression of their enzymes in the hippocampus. KMO heterozygous mice were used to investigate stress vulnerability. We also evaluated the effect of nicotine (s.c.) on CUMS-induced behavioural changes and an increase in serum corticosterone (CORT) concentration. CUMS decreased social interaction time but increased immobility time under tail suspension associated with increased serum corticosterone concentration. CUMS increased KYNA levels via KMO suppression with microglial decline in the hippocampus. Kmo+/- mice were vulnerable to stress: they exhibited social impairment and increased serum corticosterone concentration even after short-term CUMS. Nicotine attenuated CUMS-induced behavioural changes and increased serum corticosterone concentration by inhibiting the increase in corticotropin-releasing hormone. Methyllycaconitine (α7nACh antagonist) inhibited the attenuating effect of nicotine. CUMS-induced behavioural changes and the HPA axis dysregulation could be induced by the increased levels of KYNA via KMO suppression. KYNA plays an important role in the pathophysiology of MDD as an α7nACh antagonist. Therefore, α7nACh receptor is an attractive therapeutic target for MDD.

SEX DIFFERENCES IN SYSTEMIC INFLAMMATORY RESPONSE IN LOW HYPOXIA-RESISTANT RATS

OBSERVATION. Individual differences in hypoxia tolerance and expression of the hypoxia-inducible factor, HIF-1α, were found in humans and laboratory animals. This allowed us to distinguish groups of animals with low and high resistance to oxygen deficiency. It was shown that low hypoxia-resistant animals are characterized by a more severe course of the systemic inflammatory response (SIR). Sex differences in the severity of SIRS in animals with low hypoxia tolerance have not been studied. OBJECTIVE To characterize morphological and molecular-biological features of lipopolysaccharide (LPS)-induced SIR in low hypoxia-resistant male and female Wistar rats. MATERIALS AND METHODS. Low hypoxia-resistant animals were distinguished by the time of “life” in a hypobaric barocamera at an altitude of 11500 m (less than 60 s). SWO was modeled by intraperitoneal injection of LPS at a dose of 1.5 mg/kg. One day later, morphologic changes in the lungs, liver, and thymus, as well as endotoxin levels, corticosterone, HIF1-α, and TGFβ concentrations in serum from low hypoxia-resistant female and male Wistar rats were evaluated. RESULTS. Differences were found in control groups in females and males of low hypoxia-resistant rats, characterized by higher HIF1-α, corticosterone and endotoxin levels in serum in females. Thus, in females 24 h after LPS injection the number of neutrophils in interalveolar septa of lungs was higher and acute accidental involution of thymus with narrowing of subcapsular zone without changes in volumetric fraction of cortical substance developed. Whereas in males widespread pathological changes in the liver and more pronounced manifestations of accidental involution accompanied by narrowing of the volume fraction of the thymus cortical substance were revealed. In the blood serum of females with SWO, the content of corticosterone increased, while in males the concentration of HIF1-α and the level of endotoxin increased, and the content of TGFβ decreased. CONCLUSIONS. Although female and male rats were characterized by low resistance to hypoxia, the course of LPS-induced SWO and the development of immune reactions in animals have sex differences.

Ameliorative effect of phenolic compound-pterostilbene on corticosterone-induced hepatic lipid metabolic disorder in broilers

The aim of this study was to investigate the ameliorative effects of pterostilbene (PTE), a polyphenolic compound, on stress-induced lipid metabolic disorders in the liver of broiler chickens. Six hundred healthy, one-day-old Arbor Acres (AA) with similar weight were randomly assigned to five groups, each consisting of 8 replicates with 15 broilers per replicate. The groups included: a control group (fed a basal diet), and four groups treated with corticosterone (CORT) at varying dietary levels of PTE supplementation: CORT (0 mg/kg PTE), CORT-PT200 (200 mg/kg PTE), CORT-PT400 (400 mg/kg PTE), and CORT-PT600 (600 mg/kg PTE). The results indicated that PTE administration to corticosterone (CORT)-injected broilers significantly improved weight gain, reduced liver index, and lowered the elevation of serum AST, GGT, Glu, TC, TG, and LDL-c concentrations induced by CORT injection (P < 0.05), but had no significant effect on serum CORT concentration (P > 0.05). PTE also significantly reduced the increased rate of abdominal fat deposition induced by CORT, decreased the average size of adipocytes, and downregulated the expression of the FAS gene (P < 0.05). It reversed the increase in liver TC, TG, LDL-c, and NEFA content induced by CORT (P < 0.05). PTE had no significant effect on the expression of the glucocorticoid receptor GR (P > 0.05), but significantly upregulated the protein expression of Sirt1 and p-AMPK (P < 0.05), promoted the expression of lipid autophagy genes MAP1LC3B and lipolytic genes LPL, but inhibited the expression of fatty acid synthesis genes SREBP-1c, ACC, and SCD (P < 0.05). The addition of PTE to the diet alleviated CORT-induced oxidative stress and inflammation by enhancing T-SOD and GSH-Px activities, reducing MDA content, inhibiting p-NF-κB p65 and NLRP3 expression and the release of TNF-α and IL-1β in the serum, and increasing IL-4 content (P < 0.05). Overall, dietary PTE effectively regulates lipid metabolism and antioxidant status, offering a potential strategy to mitigate stress-induced metabolic disruptions in broilers.

Effect of a Broiler-Specific Light Spectrum on Growth Performance and Adrenocortical Activity in Chickens: A Pilot Study on a Commercial Farm.

This study evaluated the effect of a broiler-specific light spectrum on productive performance corticosterone (fCC) and androgen dehydroepiandrosterone (fDHEA) concentrations in feathers, and glucocorticoid (GCMs) and androgen (AMs) metabolites in droppings of broilers. Two groups of female Ross 308 broilers were reared under white LED (WL, n = 9000) and broiler-specific LED (BSL, n = 9000) lights. The body weight (BW) of 150 randomly selected animals/groups was measured weekly. Droppings and feathers were collected at the end of the cycle (29 days) from 20 animals/group. The BSL group showed higher final BW than WL (1407 ± 11 vs. 1341 ± 15 g, respectively; p < 0.001) and higher indices of uniformity (76.8% vs. 61.2% animals in the 10% around the mean, respectively; p < 0.001). No difference between groups was found in fCC and fDHEA concentrations or in the fCC-fDHEA, indicating similar long-term HPA axis activity during the cycle. A higher concentration of GCMs was found in the BSL group, indicating higher glucocorticoid secretion before sampling, with neither a difference in AMs nor in GCMs-AMs. Finally, there was a positive correlation between fCC and fDHEA and between GCMs and AMs (p < 0.01). Our findings suggest that the use of broiler-specific light improved the productivity performances of chickens without long-term consequences on HPA activation. However, the results of this pilot study in a commercial farm setting must be interpreted with caution and need confirmation.

Chronic g-CSF increases the neutrophil-lymphocyte ratio and decreases plasma corticosterone concentrations in Peromyscus maniculatus without impacting compulsive-like stereotypy

Increasing evidence points to brain-immune mechanisms underlying conditions characterized by neurocognitive rigidity. However, causal evidence remains elusive. Thus, the present work first aimed to investigate the naturalistic associations between rigid motor stereotypy and non-specific markers of systemic inflammation, i.e., the neutrophil-lymphocyte ratio (NLR) and plasma corticosterone concentrations in deer mice. We then explored causal immune-brain interactions by bolstering the NLR, using the recombinant human granulocyte colony-stimulating factor (g-CSF), i.e., pegfilgrastim (Peg). One-hundred and twenty (120) 3-week-old deer mice (both sexes) were exposed to nine weekly injections with normal water for injection or Peg (n = 60 per group) and then assessed for stereotypical expression. Stereotypical behaviour, the NLR, and plasma corticosterone were then measured. Our findings show that 1) NLR and plasma corticosterone concentrations do not predict stereotypical expression and 2) chronic Peg exposure significantly increased the NLR and decreased the plasma corticosterone concentration in mice of both sexes, without impacting stereotypical expression. While valuable findings related to the relationship between exogenous NLR manipulation and immune system functioning were highlighted, continued investigation will be necessary to further explore whether spontaneous stereotypy in deer mice may be associated with immune-inflammatory involvement.

The effect of group size and laying month on the quality, IgG, and corticosterone levels of goose eggs

Abstract. Environmental stress is known to negatively affect poultry health, production, and egg quality. Our study aimed to evaluate the effects of two different group sizes and the laying month on egg quality characteristics as well as the effect of group size on corticosterone and IgG levels in goose eggs. The research was conducted on a semi-free-range goose breeder farm in Hajdú–Bihar county, Hungary. The eggs included in the analysis were produced by 4-year-old geese of the Grimaud breed. Two group sizes were constructed; the large group contained 850 birds; and there were three small groups, each containing 50 geese as replicates. The effect of the laying month and group size on egg quality parameters and the effect of group size on egg IgG and corticosterone contents were investigated. Eggs laid in January at the peak of production and at the end of February (low-production period) were involved in the study. Regarding the effect of months, we noticed a decrease in egg width (from 6.12 to 5.98 cm), shell thickness (from 0.76 to 0.61 mm at the blunt end, from 0.69 to 0.61 mm at the equator, and from 0.65 to 0.56 mm at the pointed end), shell weight (from 19.56 to 18.19 g), yolk weight (from 69.05 to 62.35 g), yolk ratio (from 36.45 % to 34.43 %), yolk diameter (from 7.09 to 6.59 cm), and yolk colour with fan (from 12.58 to 11.83) and b∗ (from 54.57 to 49.91) (P ≤ 0.05). The albumen ratio and yolk pH increased from 53.24 % to 55.51 % and from 6.18 to 6.29 from January to February, respectively. Regarding group size, the albumen pH (8.77 vs. 8.67), IgG (4955 vs. 3823 ng mL−1), and corticosterone (187.26 vs. 76.24 ng mL−1) levels were higher in the small groups (P ≤ 0.05).

Non-Invasive Monitoring of Corticosterone Levels in Mouse Urine with Liquid Chromatography-Electrospray Ionization-Tandem Mass Spectrometry.

An innovative method for the quantification of corticosterone in the urine of C57BL/6J mice by liquid chromatography-electrospray ionization-tandem mass spectrometry was developed. Unconjugated and glucuronidated corticosterone was detected in the urine samples using enzymatic hydrolysis following liquid-liquid extraction. After optimization of the extraction protocol and LC-MS/MS parameters, we performed a validation study using a representative urine pool of C57BL/6J and Naval Medical Research Institute mice. The method shows good linearity (1-5000 fmol/µL) and the calculated limit of quantification amounts to 0.823 fmol/µL. Both intra-day and inter-day variation was ≤10%, while their recoveries amounted to 90.4-110.6% and 99.8%, respectively. Twenty-four hour urine collection of C57BL/6J mice restrained in two different metabolic cage types for two times was used to test the validated method. To control the hydration level of mice, the corticosterone concentration in their urine was normalized to urinary creatinine concentration. Our LC-MS/MS method represents a highly specific analytical tool for the quantification of corticosterone levels in urine samples, assisting in non-invasive monitoring of acute stress levels in laboratory mice.

Proof of concept for a superior therapeutic index of corticosterone compared with hydrocortisone in patients with congenital adrenal hyperplasia.

Outcomes are poor for patients with congenital adrenal hyperplasia (CAH), in part due to the supraphysiological glucocorticoid doses required to control adrenal androgen excess. Hydrocortisone (ie, cortisol) is the recommended glucocorticoid for treatment of CAH. However, the other endogenous glucocorticoid in humans, corticosterone, is actively transported out of metabolic tissues such as adipose tissue and muscle, so we hypothesized that corticosterone could control adrenal androgens while causing fewer metabolic adverse effects than hydrocortisone. Thirteen patients (8 female, 5 male) with CAH due to 21-hydroxylase deficiency completed a randomized placebo-controlled crossover study comparing 5 h intravenous infusions of either hydrocortisone, corticosterone or placebo. 6-6[2H]2-glucose and 1,1,2,3,3-[2H]5-glycerol were infused to measure glucose and glycerol kinetics, and blood samples were collected throughout. Subcutaneous abdominal adipose tissue biopsies were obtained at the end of each infusion. During the infusion, corticosterone and hydrocortisone similarly reduced ACTH, 17α-hydroxyprogesterone, androstenedione, and testosterone (in females only) compared with placebo. Despite achieving circulating corticosterone concentrations ∼2.5-fold higher than hydrocortisone, by T + 300 min hydrocortisone but not corticosterone increased glucose and insulin concentrations and reduced 6-6-[2H]2-glucose clearance compared with placebo. Hydrocortisone increased mRNA levels of the glucocorticoid regulated transcript PER1 in adipose to a greater extent than corticosterone. Corticosterone acutely controls biochemical markers of androgen excess similarly to hydrocortisone but without inducing markers of glucocorticoid "toxicity" in CAH. These data demonstrate proof of concept that corticosterone may be a safer glucocorticoid replacement than current medications, although further research is required to assess the longer-term effects of corticosterone replacement.

Effect of Stocking Density on Selected Blood Physiological, Biochemical and Enzymatical Variables of Broilers Grown to 3 kg under Antibiotic-free Conditions

Background: Reducing stocking densities may play a key role in minimizing difficulties such as physiological welfare when reducing or ending antimicrobials in poultry diets. As the demand for poultry and associated products increases, one of the major concerns centers on the question of whether stocking density influences welfare responses that are characteristic of physiological welfare. This study investigated the effect of stocking density on selected blood physiological variables along with plasma biochemistry variables and enzymes activities of broilers fed antibiotic-free diets grown to 3 kg. Methods: A total of 888 1-d-old Ross ´ Ross 708 chicks were randomly distributed into 24 pens based on stocking density treatments assignment. The treatments consisted of 4 densities (29, 33, 39 and 42 kg/m2) with six replicates. Treatments were blocked within the room to account for any variations in room conditions. Treatment assignments were randomized within each block. Used litter bedding was obtained from commercial farms to mimic commercial conditions and litter microflora. Birds were provided a three phase-feeding program (Starter: 0-14 d, Grower: 15-28 d and Finisher: 29-42 d) antibiotic-free diets. Feed and water provided ad libitum. Blood samples were collected from the brachial wing vein of 3 males and 3 females’ birds per pen on d 28 and 42 and analyzed immediately for blood physiological variables. Blood plasma samples were analyzed for T3, T4, corticosterone, biochemical variables and enzyme activities. Result: The only effect of stocking density was observed on partial pressure of CO2 (pCO2) and uric acid which were within physiological ranges for this species. However, blood glucose and plasma corticosterone concentrations were not affected by stocking density, suggesting no signs of physiological stress. Stocking densities up to 42 kg/m2 with proper environmental management may be suitable for both poultry integrators and contract growers to enhance broilers production efficiency without compromising the welfare of broilers grown to 3 kg body weight.

Reptiles as Experimental Models: Uncovering Their Role in Drug Development and Health Research

Experimental animal models are indispensable as they help to enhance the understanding of unknown diseases and contribute to new discoveries through their physiology, which facilitates the learning process and scientific dissemination. Consequently, the techniques applied to animal models require the development of guidelines that ensure respect for these animals and the reliability of the results obtained, in order to promote the advancement of scientific progress. With this in mind, the aim of the present study was to conduct a review on the use of reptiles as experimental models. The works were reviewed and selected based on their use of animals (reptiles) as experimental models and for having results relevant to the development of science and its various applications. In this context, analyzes that adhered to these principles were also considered, revealing that certain species of snakes, lizards, and turtles show promise for research in pharmaceuticals, the production of medicines and vaccines, as well as in seeking solutions to other problems related to animal health, for example, the study of baseline corticosterone (CORT) concentrations in rattlesnakes. Thus, we can conclude that, although these animals are not as commonly used in experimental research, reptiles hold an important position among vertebrates for investigating the progression of serious diseases, as well as for the development of vaccines and medications.

Disturbance by jet boating increases corticosterone concentrations in the black-backed gull (Larus dominicanus)

ABSTRACT Recreational activities such as jet boating have the potential to disturb native birds that rely on braided river habitats. To examine whether jet boating affects levels of glucocorticoid hormones, which can increase in animals under stress, we compared concentrations of corticosterone in the faeces of nesting black-backed gulls (Larus dominicanus) between days with differing levels of jet boat activity and to a nearby braided river site with no jet boating. The corticosterone titers of gull faeces sampled on the weekends (when jet boating activity was high) were almost twice that collected in the same area during the week (when jet boating activity was low). Corticosterone titers were also lower in the site without jet boating. Corticosterone levels were not significantly related to whether faeces were sampled in the centre or margin of the colony, nor did they vary significantly with number of birds in the colony. It is not known if increased concentrations of corticosterone have any negative effects on the survival or reproductive success of black-backed gulls, but our results suggest that the disturbance created by jet boating has the potential to alter hormone levels in this and perhaps other species that occur in braided river habitats.

Voluntary food restriction does not affect circulating corticosterone in obesity-prone or -resistant male and female rats

Food restriction in rodents can increase circulating corticosterone, which reflects activation of physiological stress responses. These responses affect a myriad of behaviors and physiological processes and can increase the risk of obesity. Most studies in this area have used experimenter-imposed restriction. However, rats will voluntarily restrict their food intake if they are returned to chow after a period of access to sugary, fatty “junk food” (JF) diet. Here we examine the effects of voluntary food restriction in obesity-prone and -resistant male and female rats on circulating corticosterone concentrations and determine whether corticosterone release in response to acute stress differs in groups with a history of JF consumption.

3,5-Dihydroxy-4-methoxybenzyl alcohol, a novel antioxidant isolated from oyster meat, inhibits the hypothalamus–pituitary–adrenal axis to regulate the stress response

BackgroundAntioxidants that can scavenge reactive oxygen in the brain and inhibit hyperactivity of the HPA axis are desirable. AimsWe investigated the cerebral translocation of the antioxidant 3,5-dihydroxy-4-methoxybenzyl alcohol (DHMBA) and the effects of DHMBA administration on the hypothalamus–pituitary–adrenal (HPA) axis in stress-loaded rats. MethodsExperiment 1: Plasma and brain DHMBA concentrations were measured over time after oral DHMBA administration to male B6 mice. Experiment 2: Female Wistar Imamichi rats were used. The normal group was not subjected to stress. The stress, DHMBA, and vitamin E groups were subjected to individual and overcrowding stress. Brain and hippocampal 8-hydroxy-2′-deoxyguanosine levels, hippocampal glucocorticoid receptor-α levels, plasma corticosterone levels and RNA levels of glutathione peroxidase 4, catalase, and glutathione reductase in the hippocampus were measured. ResultsIn Experiment 1, DHMBA was not detected in the plasma or brain before DHMBA administration but was detected in both after administration. In Experiment 2, brain and hippocampal 8-hydroxy-2′-deoxyguanosine levels and plasma corticosterone levels were significantly lower in the DHMBA than in the stress group. Glucocorticoid receptor-α levels were higher in the DHMBA than in the stress group. DHMBA increased RNA levels of antioxidant enzymes in the hippocampus. Conclusion: DHMBA was translocated to the brain after administration. DHMBA administration decreased 8-hydroxy-2′-deoxyguanosine levels in the brain and hippocampus, increased hippocampal glucocorticoid receptor-α levels, and decreased the plasma corticosterone concentration, suggesting that DHMBA inhibits hyperactivity of the HPA axis. Nrf2 pathway activity induced by DHMBA resulted in increased antioxidant enzyme levels in the hippocampus.