Differences In Corticosterone Responses Research Articles

Investigating Krtcap3 as a novel stress gene

While obesity is an increasingly prevalent disease, genetic susceptibility is poorly understood and more research is sorely needed. Our lab has sought to confirm Keratinocyte-associated protein 3 ( Krtcap3) as a novel adiposity gene and characterize its role using an in vivo whole-body knock-out (KO) model on the Wistar-Kyoto (WKY) rat strain.We obtained conflicting adiposity and food intake results between two in vivo studies conducted before and after the COVID-19 pandemic, which brought along drastic environmental changes in the animal facility. Compared to pre-pandemic, in the quieter post-COVID-19 environment wild-type (WT) rats were eating more and gaining more weight, without corresponding changes in KO rats. We hypothesized that the prior environment had affected the stress levels of the rats, and that Krtcap3 may be a novel stress-related gene whose effects on adiposity are tangential.A significant environmental change was supported by altered expression of genes associated with glucocorticoid metabolism. Most interestingly, KO rats consistently have lower basal corticosterone (CORT) compared to WT rats and have a much stronger increase in CORT when their cage mate is removed for euthanasia.We have since sought to characterize the role Krtcap3 may play in the stress response. Despite the genotype differences in CORT response seen at euthanasia, there were no differences in the CORT response during a restraint test, indicating that both WT and KO are capable of responding to acute stressors. In WKY rats, there is high Krtcap3 expression in the pituitary gland and along the gastrointestinal tract, suggesting potential tissues of action for further investigation. Surprisingly, when we exposed WT and KO rats long-term to white noise and unpredictable mild stress, there was a stronger increase in the anxiety response of KO rats as compared to WT. This supports that Krtcap3 expression affects the response to stress, but suggests that the type of stress may also play a role. Taken together, these data demonstrate that Krtcap3 participates in the stress response. Though more work is needed to elucidate the finer mechanisms of the role of Krtcap3, these findings have important implications for human health, where stress is a known co-morbidity for many diseases, including obesity. R01 DK106386, T32 DA041349 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Male Goal-Tracker and Sign-Tracker Rats Do Not Differ in Neuroendocrine or Behavioral Measures of Stress Reactivity.

Environmental cues attain the ability to guide behavior via learned associations. As predictors, cues can elicit adaptive behavior and lead to valuable resources (e.g., food). For some individuals, however, cues are transformed into incentive stimuli and elicit motivational states that can be maladaptive. The goal-tracker (GT)/sign-tracker (ST) animal model captures individual differences in cue-motivated behaviors, with reward-associated cues serving as predictors of reward for both phenotypes but becoming incentive stimuli to a greater degree for STs. While these distinct phenotypes are characterized based on Pavlovian conditioned approach (PavCA) behavior, they exhibit differences on a number of behaviors relevant to psychopathology. To further characterize the neurobehavioral endophenotype associated with individual differences in cue-reward learning, neuroendocrine and behavioral profiles associated with stress and anxiety were investigated in male GT, ST, and intermediate responder (IR) rats. It was revealed that baseline corticosterone (CORT) increases with Pavlovian learning, but to the same degree, regardless of phenotype. No significant differences in behavior were observed between GTs and STs during an elevated plus maze (EPM) or open field test (OFT), nor were there differences in CORT response to the OFT or physiological restraint. Upon examination of central markers associated with stress reactivity, we found that STs have greater glucocorticoid receptor (GR) mRNA expression in the ventral hippocampus, with no phenotypic differences in the dorsal hippocampus or prelimbic cortex (PrL). These findings demonstrate that GTs and STs do not differ on stress-related and anxiety-related behaviors, and suggest that differences in neuroendocrine measures between these phenotypes can be attributed to distinct cue-reward learning styles.

The effects of light stimulation during incubation on indicators of stress susceptibility in broilers

Providing light during incubation has been shown to decrease bilateral physical asymmetry of broilers posthatch, which may indicate that early light stimulation reduces later stress susceptibility. This experiment evaluated the effects of lighting during embryogenesis on other measures of stress responsiveness in broilers. Cobb 500 eggs (n = 1,404) were incubated under 0L:24D, 1L:23D, 6L:18D, or 12L:12D; the light level was 550 lx. The broilers were then raised in floor pens under a 12L:12D lighting regimen, and various stress parameters were measured during wk 3 to 6 of age. There was an effect of incubation lighting regimen on posthatch stress responses. Following 1 h of crating, the change in corticosterone (CORT) concentration was less in the 12L:12D (−0.06 ng/mL, P < 0.05) treatment than all other treatments (pooled mean = 0.24 ng/mL); however, there were no treatment differences in CORT response to adrenocorticotropic hormone administration (pooled mean pre- vs. 1 h postadministration = 17.5 ng/mL, P > 0.05). Anti-keyhole limpet hemocyanin titers were higher in the 12L:12D birds (92,395 units/mL; P < 0.05) than all other treatments (pooled mean = 68,407 units/mL) on d 1 postcrating. Additionally, composite asymmetry scores were lower in the 12L:12D treatment (0.92 mm) than all other treatments (pooled mean = 1.14 mm, P < 0.05). These results demonstrate that providing 12 h of light per day during incubation can reduce the stress susceptibility of broilers posthatch.

Adrenocortical control in the neonatal rat: ACTH- and cAMP-independent corticosterone production during hypoxia

We have previously demonstrated that the neonatal corticosterone response to acute hypoxia shifts from ACTH independence to ACTH dependence between postnatal days two (PD2) and eight (PD8). Cyclic AMP (cAMP) is the obligatory intracellular second messenger of ACTH action, and we hypothesized that corticosterone production in neonatal rats shifts from a cAMP-independent mechanism to cAMP-dependent mechanism between PD2 and PD8. Plasma ACTH and corticosterone and adrenal cAMP and cGMP responses to acute severe hypoxia (8% O2 for 5, 10, 20, 30, and 180 min) were measured in neonatal rats at PD2, PD8, and PD15. Plasma ACTH and corticosterone were measured by radioimmunoassay, and adrenal cAMP and cGMP were measured by ELISA. Plasma corticosterone-binding globulin (CBG) was measured in normoxic pups by ELISA. The largest corticosterone response was observed in PD2 pups, despite only a small increase in plasma ACTH that was not sustained. The PD2 ACTH-independent increase in corticosterone occurred with no change in adrenal cAMP or cGMP content. Plasma CBG concentration was lowest in PD2 pups. Large corticosterone responses were measured during the first 30 min of hypoxia. Differences in corticosterone responses between PD2 and PD8 pups cannot be attributed to changes in plasma protein binding capacity, and the PD2 corticosterone response is consistent with a nongenomic mechanism of action. We conclude that the sustained corticosterone response to hypoxia in PD2 pups occurs with small and transient ACTH responses and independently of increases in adrenal cAMP or cGMP.

Transgenerational transmission of anxiety induced by neonatal exposure to lipopolysaccharide: Implications for male and female germ lines

Neonatal lipopolysaccharide (LPS) exposure increases anxiety-like behaviour and alters neuroendocrine responses to stress in adult rats. The current study assessed whether this anxiety-related phenotype observed in rats neonatally exposed to LPS is transferable to subsequent generations. Wistar rats were exposed to LPS (0.05 mg/kg, Salmonella enteritidis) or non-pyrogenic saline (equivolume) on postnatal days 3 and 5. In adulthood, animals were subjected to restraint and isolation stress or no stress, and subsequently evaluated for anxiety-like behaviours on the elevated plus maze, acoustic startle response, and holeboard apparatus. Blood was collected to examine corticosterone responses to stress and behavioural testing in adulthood. Animals from both treatment groups which exhibited the anxiety-like phenotype were bred with untreated partners. Maternal care of the second generation (F2) was monitored over the first week of life. In adulthood, the F2 generation underwent identical testing procedures as the parental (F1) generation. The F2 offspring of females exposed to LPS as neonates exhibited an anxiety-like phenotype in adulthood and a potentiated corticosterone response to stress (p<.05). F2 offspring of males exposed to LPS as neonates also exhibited an anxiety-like phenotype (p<.05), however, no differences in corticosterone responses were observed. To determine the impact of maternal care on the anxiety-like phenotype, a cross-fostering study was conducted in which offspring of LPS-treated females were fostered to saline-treated mothers and vice versa, which was found to reverse the behavioural and endocrine phenotypes of the F2 generation. These data indicate that a neonatally bacterially induced anxiety phenotype is transferable across generations in both sexes. Maternal care is the mediating mechanism along the maternal line. We suggest that transmission may be dependent upon heritable epigenetic phenomena for the paternal line. The implications of this study apply to potential neuroimmune pathways through which psychopathology may be transmitted along filial lines.

Effects of maternal corticosterone and stress on behavioral and hormonal indices of formalin pain in male and female offspring of different ages

In previous studies, we showed for the first time that prenatal stress in rats produces long-term alterations of formalin-induced pain behavior that are dependent on age and sex, and we demonstrated an important role of the serotonergic system in mechanisms of prenatal stress (Butkevich, I.P. and Vershinina, E.A., 2001; Butkevich, I.P. and Vershinina, E.A., 2003; Butkevich, I.P., Mikhailenko, V.A., Vershinina, E.A., Khozhai, L.I., Grigorev, I.P., Otellin, V.A., 2005; Butkevich, I.P., Mikhailenko, V.A., Khozhai, L.I., Otellin, V.A., 2006). In the present study, we focus on the influence of the maternal corticosterone milieu and its role in the effects of stress during pregnancy on formalin-induced pain and the corticosterone response to it in male and female offspring of different ages. For this purpose, we used adrenalectomy (AD) in female rats 3–4 weeks before mating (as distinct from AD typically performed at the beginning of pregnancy). Since AD is considered a reliable method to treat hypercortisolism, researches on the effects of long-term AD in dams on the systems responsible for adaptive behavior in offspring are important (such studies are not described in the literature). The results demonstrate that the differences in the corticosterone response to injection of formalin and saline are obvious in 90-day-old (adult) female offspring but masked in 25-day-old ones. AD promoted the corticosterone response to formalin-induced pain but not to injection of saline in prenatally non-stressed female offspring of both ages. Prenatal stress canceled the differences in corticosterone response to injection of formalin and saline in 25-day-old offspring of AD dams and in adult offspring of sham-operated (SH) dams but caused similar differences in adult offspring of AD dams. Sex differences were found in basal corticosterone levels in AD prenatally stressed rats of both age groups, with a higher level in females, and in the corticosterone response to formalin-induced pain in the adult rats of all groups investigated, with higher corticosterone levels in females. In regard to pain behavior, AD induced significant changes in flexing + shaking in prenatally non-stressed adult offspring and canceled the differences in this behavior between non-stressed and stressed 25-day-old offspring. There were sex differences in pain behavior of the adult rats: greater flexing + shaking in AD non-stressed males but in SH non-stressed females; greater licking in prenatally-stressed AD and SH females. These results indicate that the long-term influences of maternal corticosterone on formalin-induced pain and the corticosterone response to it are determined by the sex and age of the offspring and suggest that other mechanisms, including serotonergic ones revealed in our previous studies, are involved in the effects of prenatal stress on inflammatory pain behavior.

Corticosterone Responses to Capture and Restraint in Emperor and Adelie Penguins in Antarctica

Birds respond to capture, handling and restraint with increased secretion of corticosterone, a glucocorticoid hormone that helps birds adjust to stressful situations. Hoods are reported to calm birds, but possible effects of hoods on corticosterone responses have not been reported for any bird. Corticosterone responses to restraint in Adelie penguins held by their legs with their head covered by a hood were markedly lower than responses of penguins restrained in a mesh bag inside a cardboard box (corticosterone at 30 min 15.69+/-1.72 cf. 28.32+/-2.75 ng/ml). The birds restrained by the two methods were sampled at the same location but in different years, so the differences in corticosterone responses cannot unequivocally be ascribed to an effect of hoods to reduce corticosterone responses. Corticosterone responses have been measured in some penguins, but not in the largest, the emperor penguin (Aptenodytes forsteri). The relationship between body mass and corticosterone responses to capture and restraint in penguins was examined in emperor penguins captured on sea ice in McMurdo Sound and Adelie penguins (Pygoscelis adeliae) captured at Cape Bird, Ross Island, Antarctica. Total integrated corticosterone responses were higher in the emperor than the Adelie penguins, but corrected integrated corticosterone responses, which represent the increase in corticosterone from initial concentrations and hence the corticosterone response to restraint, were the same. The results for the emperor and Adelie penguins, together with data from other penguin species, suggest that there is no relationship between the size of corticosterone responses and body mass in penguins.

Corticosterone Responses of Grey‐Faced Petrels (Pterodroma macroptera gouldi) Are Higher during Incubation than during Other Breeding Stages

We report the results of the first field study examining seasonal changes in corticosterone responses of typically long-lived birds of the order Procellariiformes. In particular, we examined whether grey-faced petrels Pterodroma macroptera gouldi showed changes in circulating baseline corticosterone concentrations and corticosterone responses to a standardized handling protocol across the breeding season. Such changes have been associated with changes in body condition and variations in energy demands on adult birds through the breeding season. During early incubation, males were in significantly better condition than females that had just completed laying, whereas during late incubation, males were in significantly poorer condition than females. In spite of these differences, there was no significant difference in baseline corticosterone concentrations between sexes or among birds at different reproductive stages. However, we detected significant differences in corticosterone responses associated with a standardized handling protocol at different stages through the breeding season. Responses were significantly greater during incubation compared with the prelay period and late chick rearing. Body condition was weakly and negatively correlated with maximum and total integrated corticosterone level, indicating that some of the individual variability in stress corticosterone responses could be explained by variation in body condition. However, the largest stress response occurred during late incubation and was independent of sex, although males were in relatively poor condition and females in relatively good condition. This period coincided with the breeding stage in which energy constraints on individual adults were higher than at other periods of the reproductive cycle and birds may be physiologically primed for extended fasts.

Gender, Sex Steroids, Corticotropin-Releasing Factor, Nitric Oxide, and the HPA Response to Stress

We used two stresses—exposure to mild electrofoot shocks (a neurogenic stress) and acute alcohol injection (a systemic stress)—to investigate the influence of gender and circulating sex steroids on ACTH and corticosterone released by adult rats. Both types of stresses significantly increased plasma levels of these hormones. Following exposure to shocks, intact females secreted significantly more ACTH than intact males, a difference that was abolished by ovariectomy. Gender differences in corticosterone responses were sometimes, but not always, present. In contrast, in this series of experiments males released more ACTH when acutely injected with alcohol, while there was no obvious effect of sex on corticosterone secretion. Corticotropin-releasing factor (CRF) antagonists were more effective at reducing ACTH compared to corticosterone levels. Finally, pituitary response to CRF, but much less so to vasopressin (VP), was larger in intact females compared to intact males. Blockade of endogenous nitric oxide formation slightly enhanced the effect of CRF in males, but not in females, and while it produced the expected enhancement of VP-induced ACTH release, this effect was more pronounced in females. Collectively, these results provide evidence for an influence of circulating sex steroids on pituitary and adrenal activity under some, but not all circumstances.

Reproductive effects in F1-generation rats perinatally exposed to PCB126, PCB 118, PCB 153 or 2,3,4,7,8-PnCDF

Neonatal lipopolysaccharide (LPS) exposure increases anxiety-like behaviour and alters neuroendocrine responses to stress in adult rats. The current study assessed whether this anxiety-related phenotype observed in rats neonatally exposed to LPS is transferable to subsequent generations. Wistar rats were exposed to LPS (0.05 mg/kg, Salmonella enteritidis) or non-pyrogenic saline (equivolume) on postnatal days 3 and 5. In adulthood, animals were subjected to restraint and isolation stress or no stress, and subsequently evaluated for anxiety-like behaviours on the elevated plus maze, acoustic startle response, and holeboard apparatus. Blood was collected to examine corticosterone responses to stress and behavioural testing in adulthood. Animals from both treatment groups which exhibited the anxiety-like phenotype were bred with untreated partners. Maternal care of the second generation (F2) was monitored over the first week of life. In adulthood, the F2 generation underwent identical testing procedures as the parental (F1) generation. The F2 offspring of females exposed to LPS as neonates exhibited an anxiety-like phenotype in adulthood and a potentiated corticosterone response to stress (p < .05). F2 offspring of males exposed to LPS as neonates also exhibited an anxiety-like phenotype (p < .05), however, no differences in corticosterone responses were observed. To determine the impact of maternal care on the anxiety-like phenotype, a cross-fostering study was conducted in which offspring of LPS-treated females were fostered to saline-treated mothers and vice versa, which was found to reverse the behavioural and endocrine phenotypes of the F2 generation. These data indicate that a neonatally bacterially induced anxiety phenotype is transferable across generations in both sexes. Maternal care is the mediating mechanism along the maternal line. We suggest that transmission may be dependent upon heritable epigenetic phenomena for the paternal line. The implications of this study apply to potential neuroimmune pathways through which psychopathology may be transmitted along filial lines.

Diurnal variation in resting levels of corticosterone is not mediated by variation in adrenal responsiveness to adrenocorticotropin but involves splanchnic nerve integrity.

To study possible mechanisms controlling diurnal changes in corticosterone (CORT) levels, we tested the CORT responses to ACTH in the morning (AM) and evening (PM) in male Wistar and Sprague-Dawley rats. Rat ACTH-(1-39) or human ACTH-(1-24) (3.75-15 ng/rat) was given as an iv bolus or an intraarterial infusion to (un)anesthetized rats treated with dexamethasone (0.1-0.5 mg/kg, 2-6 h before ACTH). In all conditions studied, no AM/PM differences in CORT responses were found when ACTH was given in vehicle (pH 4.3-7). This contrasts with earlier studies in which ACTH was given in a strongly acid vehicle (pH 1-1.9). Administration of ACTH in such acid vehicle confirmed the reported AM/PM differences in CORT responses (P < 0.05). Because alterations in splanchnic nerve activity can modulate ACTH-induced CORT secretion, we studied the effect of splanchnic nerve transection (SPLNX) on the diurnal change in resting CORT levels in unilaterally adrenalectomized rats. SPLNX reduced resting CORT concentrations in the PM (approximately 50%; P < 0.05), but not in the AM. SPLNX did not abolish the acid vehicle-associated AM/PM differences in CORT responses to ACTH. We conclude that 1) diurnal variation in adrenal responsiveness to ACTH per se does not exist in this rat model; 2) the strongly acid vehicle interacts with ACTH-induced CORT secretion; 3) the PM rise in plasma CORT depends on the integrity of the sympathetic neural input to the adrenal gland.

Sex differences in adrenal function in the lizard Cnemidophorus sexlineatus: II. Responses to acute stress in the laboratory.

Circulating concentrations of plasma corticosterone and gonadal steroids were measured in intact and gonadectomized male and female lizards (Cnemidophorus sexlineatus) following acute stress (handling) in the laboratory. There was a significant increase in plasma corticosterone after stress. Whereas intact females exhibited greater concentrations of corticosterone relative to intact males, ovariectomized females exhibited lower concentrations of corticosterone relative to castrated males. In addition to sex differences in corticosterone responses to gonadectomy, progesterone was elevated by stress in both intact and ovariectomized females but not in males. Corticosterone adjusted for castration and handling in males was negatively correlated with the plasma androgen level. The adrenal responsiveness of males to acute stress may be attenuated by androgens presumably secreted by the testis. Not only does adrenal function influence reproduction, but adrenal responses differ between males and females, and appear to be influenced by the gonadal axis. The sex differences in adrenal responses to stress likely reflect different reproductive strategies and nutritional requirements of males and females during the breeding season.

Plasma corticosterone response of rats with sociopsychological stress in the communication box.

The purpose of present study was to investigate the physiological characteristics of sociopsychological stress induced by the communication box method. In this method, the nonfoot shocked rats were used as the psychologically stressed experimental group. In acute stress experiments, nonfoot shocked rats were exposed to emotional responses from foot shocked rats for 6 h in the light (0900-1500) or in the dark phase (2100-0300). In the light phase, the induced increase in plasma corticosterone levels of nonfoot shocked and foot shocked rats returned to corresponding control levels 6 h following the initiation of stress session, whereas those in the dark phase were significantly higher. Although there were some differences in corticosterone responses between both phases, the acute effect of sociopsychological stress was unclear. Chronic stress experiment with daily exposure for 1 h to sociopsychological stress caused the plasma corticosterone levels of nonfoot shocked rats to increase significantly not only in the postexposure level (just after stress exposure) but also in the preexposure level (before stress exposure) when naive rats were used daily as foot shocked animals. These results suggest that the repeated exposure of sociopsychological stress can induce physiological changes, and stressful situation can be established with only emotional responses from foot shocked rats.