Participation of the brain catecholamines in changes in activity of the rat hypophyseal-adrenal system induced by hydrocortisone administration during neonatal ontogenesis

Administration of hydrocortisone or 6-hydroxydopamine (6-ONDA) to little rats from the 1st to the 5th day of life affected functional activity of the hypophyseal-adrenal system (HAS) of immature rats. In the morning hours, the rats developed a decrease in the basal and stressor levels of corticosterone in the blood, whereas administration of the 6-ONDA did not change the functional activity of the HAS in the morning. The data obtained suggest that disorders in the HAS regulation by the feedback mechanism resulting from neonatal administration of hydrocortisone may be associated with a drop in the noradrenaline level in the hypothalamus.     

Disorder of catecholamine synthesis in early ontogeny and hypophyseal-adrenal cortical function in adult rats

The effects of daily intraperitoneal (150 mg/kg of body weight) injections of alpha-methyl-dl-tyrosine (MT), an inhibitor of tyrosine hydroxylase, on the 2nd to 4th, 5th to 7th or 10th to 12th days of life on the pituitary-adrenal function and brain adrenaline level in 3 to 4-month old rats were studied. MT treatment on the 5th to 7th days resulted in a decrease of noradrenaline content in hypothalamus and midbrain and chronic decrease of basal corticosterone level in blood, its diurnal fluctuations being preserved. MT injections on the 10th to 12th days were accompanied by a decrease of the basal corticosterone level, but the brain noradrenaline level remained unchanged. A study of pituitary-adrenal stress reactivity of adult rats has revealed no specific MT effect. A conclusion was drawn that the MT treatment applied exerted a long-term effect, predominantly, on the regulation of tonic corticosterone secretion.     

Expression of asparagine synthetase genes in sunflower (Helianthus annuus) under various environmental stresses.

In sunflower, asparagine synthetase (AS; EC 6.3.5.4) is encoded by a small family of three genes (HAS1, HAS1.1 and HAS2) that are differentially regulated by light, carbon and nitrogen availability. In this study, the response of each gene to various stress conditions was examined by Northern analysis with gene-specific probes in leaves and roots. The expression of HAS1 and HAS1.1 genes was induced by osmotic stress (300 mM mannitol), salt stress (150 mM NaCl), and heavy-metal stress (20 microM CuSO(4)), more in roots than in leaves. The expression of HAS2 was not significantly altered by stress treatments. The positive response of HAS1 and HAS1.1 genes to osmotic and salt stresses occurred in the light, in contrast to that previously found in unstressed plants. Measurements of sucrose and total free amino acid contents in leaves and roots indicate that the expression of root HAS1 and HAS1.1 genes in stressed plants is not under metabolic control by the intracellular C/N ratio, suggesting the involvement of some specific stress factor(s). Growth of plants at 40 degrees C for 12h negatively affected the expression of HAS1 and HAS1.1 but not that of HAS2.     

Morpho-functional alterations of the adrenal cortex in rats with active and passive strategy of adaptive behavior

In rats with the active (KHA strain) and passive (KLA strain) coping strategies, a post-stress depression develops respectfully on the 1st or 10th day after the inescapable stress. The present study revealed an increase of adrenal weight and blood corticosterone levels on a day following the inescapable stress, as well as marked fluctuations of blood glucose in one and five days post-stress in KHA rats. By the 10th day, these indices returned their basal levels. In contrast, the stress reactivity of KLA rats was lower in all terms and their corticosterone levels remained reduced on the 10th day after stress. In KLA rats, the fasciculate zone was reduced but reticulated zone grew in Ith day following the stress, while in KHA rats the inescapable stress resulted in growth fasciculate zone and concomitant reduction of reticulate zone, both evident on the 10th post-stress day. The data indicate that the development of post-stress depression in KLA rats is probably associated with exhaustion of adrenocortical function.     

Changes in hypothalamic noradrenaline and 5-hydroxytryptamine levels during the development of warm- and cold-adaptation in the rat

Hypothalamic 5-hydroxytryptamine (5-HT) and noradrenaline (NA) as well as plasma corticosterone levels were studied in male rats after 1, 2, 4 and 6 weeks of exposure to 4--7 or 30--31 degrees C. An increase of the NA concentration and a decrease of the 5-HT level was observed after the first week in both cold and warm environment together with an increase of plasma corticosterone levels in both groups. NA, 5-HT and plasma corticosterone levels returned to normal in cold-exposed animals by the 6th week whereas in warm-acclimated rats NA and corticosterone levels regained their initial values and 5-HT concentrations remained low. Changes by the end of the first week of exposure may result from the thermal stress. The low 5-HT levels of warm-adapted animals at the end of the 6th week were probably secondary to the process of adaptation.     

Dissociation between corticosterone and growth hormone adaptation to chronic stress in the rat

We have studied the effect of acute and chronic stress on corticosterone and growth hormone (GH) serum levels in male Wistar rats. Both acute noise-light stress and the presence of a dog elicited an increase in corticosterone and a decrease in GH levels in serum. While previous chronic stress induced a reduction of corticosterone response to the same stimuli, no reduction was observed in GH response. In addition, chronic exposure to noise-light stress induced modifications in corticosterone but not in GH response to dog presence. The results suggest that GH and corticoadrenal response mechanisms of adaptation to chronic stress are dissociated. This is further corroborated by the study of the correlation between both hormones.     

Repeated stress at the same time of day does not mimic timed feeding in its effects on the plasma corticosterone rhythm in rats

The present study examined whether mild restraint stress occurring at the same time each day would entrain an anticipatory peak in the circadian plasma corticosterone rhythm associated with the time of stress. Rats were stressed by tube restraint for 2 h in the morning on 23 consecutive days, and plasma corticosterone concentrations were measured at 4h intervals over the next 2 days. Plasma corticosterone patterns were similar in control and restrained rats, and no anticipatory corticosterone peak occurred in stressed rats before the time when stress would have occurred. However, periodic regression analysis of the data indicated that timed stress did advance the acrophase of the circadian corticosterone rhythm by 1.7 h. This effect was minimal and could not explain the anticipatory rise in corticosterone concentrations seen in restricted feeding paradigms. Thus, it is unlikely that any stress associated with restricted feeding entrains corticosterone rhythms to anticipate the time of feeding, and some aspect of feeding per se is likely involved in producing the corticosterone peak that anticipates the time of restricted feeding.     

Inhibition of the ACTH adrenal response to stress by treatment with hydrocortisone, prednisolone and dexamethasone in the rat

16- and 4-week-old intact and adrenalectomized rats have been treated with different doses of the three glucocorticoids hydrocortisone, prednisolone and dexamethasone by gavage. The delayed feedback effect on plasma ACTH and corticosterone response to an ether stress have been assessed. Almost complete suppression of corticosterone response 20 min after an ether stress and an ACTH suppression to 20% of control values 5 min after an ether stress were observed with 25 micrograms of dexamethasone, 10 mg of prednisolone and 20 mg of hydrocortisone. Although the percent inhibition of corticosterone and ACTH response to stress was comparable, a striking dissociation of the ACTH and corticosterone release was observed in terms of absolute concentrations. A mean ACTH concentration of 462 ng/l after 25 micrograms of dexamethasone was measured together with a barely measurable corticosterone concentration of 3 micrograms%. Similarly, after 10 mg of prednisolone, the mean ACTH concentration was 404 ng/l, whilst the mean corticosterone concentration was 3 micrograms%. This dissociation demonstrates that the corticosterone concentration on its own does not necessarily reflect the ACTH release. At 4 weeks of age, the ACTH response to stress is more difficult to suppress than in adult animals. This is more obvious after adrenalectomy, where the excessive ACTH secretion was less inhibited by all glucocorticoids used. The time between the last steroid gavage and stress must be considered. In 4-week-old animals the ACTH response 16 h after 12.5 micrograms of dexamethasone was inhibited by 22%, whereas 4 h after the same dexamethasone dose the inhibition was 85%.(ABSTRACT TRUNCATED AT 250 WORDS)     

The neonatal glucocorticoid treatment-produced long-term changes of the pituitary-adrenal function and brain corticosteroid receptors in rats.

Two distinct periods of sensitivity to elevated glucocorticoid hormone levels during postnatal development of the pituitary-adrenal axis were studied. Wistar rats were injected subcutaneously (s.c.) with cortisol (1 mg/kg) on postnatal days 1-5 or 14-18. The steroid treatment during the first postnatal week resulted in a decrease of the morning basal and stress-induced plasma corticosterone levels in 30 day-old male rats, as well as in rats that were injected with cortisol on the third postnatal week. Stress-induced corticosterone levels in 90-day old cortisol-treated rats were determined in blood samples drawn from the tail vein before the restraint stress, immediately after the 20-min long stress, then 60 and 180 min afterwards. Only the rats treated with cortisol during the third week showed a prolonged stress-induced corticosterone secretion, with the highest corticosterone level in 180 min after the restraint stress. The early neonatal cortisol treatment had no effect on (3)H-corticosterone binding in all studied brain areas of the 90-day old rats. The rats treated with cortisol at the 14-17th postnatal days showed a significantly lower (3)H-corticosterone binding in the frontal cortex, hippocampus, and hypothalamus. These findings suggest that the third week of life in rats is more sensitive to elevated levels of corticosterone than the first one. The high level of glucocorticoids at this period has long-term effects on the efficiency of the negative feedback mechanisms provided by hypothalamus-pituitary-adrenal axis.     

Stress and body condition as prenatal and postnatal determinants of dispersal in the common lizard (Lacerta vivipara)

Dispersal is a complex phenomenon affected by multiple factors. Among the factors that influence dispersal in the common lizard (Lacerta vivipara), poor maternal body condition and stress are known to decrease dispersal propensity of juveniles. But the effect of individual factors on dispersal could change when several of them act concurrently or at different developmental stages. Prenatal factors can affect clutch and/or juvenile characteristics that later affect dispersal. Postnatal influences are mainly exerted on juvenile dispersal behavior. We investigated the role of body condition and stress on dispersal at a prenatal and a postnatal stage. Stress was mimicked by experimentally increasing corticosterone levels in pregnant females and recently born juveniles. We considered (1). the influence of maternal body condition and prenatal corticosterone treatment on clutch, juvenile characteristics and on dispersal behavior and (2). the influence of juvenile body condition and postnatal corticosterone treatment on juvenile dispersal behavior. There was an interaction between maternal condition and prenatal corticosterone treatment on juvenile dispersal. Dispersal decreased with maternal corticosterone increase only in juveniles from the more corpulent females, while it increased with juvenile body condition. Good maternal body condition affected clutch and juvenile characteristics favoring dispersal, while elevation of corticosterone level (stress) exerted the opposite effect. Juvenile body condition favored dispersal, while there was no effect of postnatal corticosterone treatment on juvenile dispersal propensity.     

Effect of social isolation on 24-h pattern of stress hormones and leptin in rats

This work analyzes the effect of social isolation of growing male rats on 24-h changes of plasma prolactin, growth hormone, ACTH and leptin, and on plasma and adrenal corticosterone concentrations. At 35 days of life, rats were either individually caged or kept in groups (6-8 animals per cage) under a 12:12 h light/dark schedule (lights on at 08:00 h). A significant arrest of body weight gain regardless of unchanged daily food intake was found in isolated rats after 2 weeks of isolation. On the 4th week, rats were killed at 6 time intervals during a 24-h cycle, beginning at 09:00 h. In isolated rats the 24-h pattern of all parameters tested became distorted, as assessed by Cosinor analysis. When analyzed as a main factor in a factorial analysis of variance, isolation decreased plasma prolactin and growth hormone, increased plasma leptin and corticosterone while decreased adrenal corticosterone. Plasma corticosterone levels correlated significantly with plasma ACTH and with adrenal corticosterone levels in group-caged rats only. These changes can be attributed to an effect of mild stress on the endogenous clock that modulates the circadian hormone release.     

Effect of corticosterone on the prolactin response to psychological and physical stress in rats

Both corticosterone and prolactin (PRL) levels increase in response to stress. In these studies we examined the effect of corticosterone on the PRL response to both physical (footshock) and psychological (novel environment) stress. Three groups of rats were used: sham adrenalectomized (SHAM), adrenalectomized (ADX), and adrenalectomized with corticosterone replacement (ADX+CORT). The corticosterone-treated animals received 80 ug corticosterone/ml drinking water. Blood samples were drawn via an indwelling cannula and PRL values determined using radioimmunoassay. ADX rats showed a consistently greater PRL response to being placed on a platform above water (novel environment) or when receiving intermittant footshock than did ADX+CORT rats. The PRL response of the latter group was similar to that of the SHAM animals. These findings indicate that corticosterone levels of an animal can significantly attenuate the magnitude of the PRL response to both physical and psychological stress. These findings further emphasize that the PRL response to stress is dependent not only upon the immediate action of the stressor, but also the prior stress history of the animal.     

The influence of nest attendance and provisioning on nestling stress physiology in the Florida scrub-jay

Stressful conditions during development may have lasting consequences for an animal's lifetime fitness. We investigated the degree to which parental provisioning and nest attendance influenced baseline levels of the stress hormone corticosterone in nestling Florida scrub-jays. Provisioning rates of male and female breeders and nest attendance of female breeders were recorded during focal watches conducted between days 3 and 5 post-hatch. A small blood sample was taken from each nestling on day 11 post-hatch and used to quantify levels of baseline corticosterone. The proportion of time spent by female breeders at a considerable distance from the nest was positively related to nestling corticosterone levels. Nestling corticosterone was also negatively related to parental provisioning rate, although this effect seemed to be secondary to the effect of the female's time away from the nest. These results indicate that parental behavior contributes to nestling stress physiology, which may in turn direct the formation of the adult phenotype and influence an individual's chances of survival.     

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

We have studied the effect of chronic noise stress (St) and ACTH administration (Ac) affecting blood pressure and plasma corticosterone levels in male Wistar rats. Both chronic treatments elicited an increase in plasma corticosterone and blood pressure levels. The blood pressure increased from the first week of treatment period in St and Ac rats and remained high 4 weeks after the end of the stress period. However, blood pressure elevation decrease progressively during the first three weeks of post-treatment in ACTH administrated rats. The rise of blood pressure levels was due to the effect of chronic treatment. This was demonstrated by the absence of differences between the two values of blood pressure measurement with and without daily treatment in both St and Ac groups. Increased corticosterone levels decreased rapidly during the post-treatment period in St and Ac rats. The results suggest a possible relationship between the development of hypertension and the Hypothalamus-Hypophysis-adrenal (HHA) axis stimulation in rats.     

Dietary Resistant Starch Alters the Characteristics of Colonic Mucosa and Exerts a Protective Effect on Trinitrobenzene Sulfonic Acid-induced Colitis in Rats

The protective effect of a dietary high-amylose cornstarch (HAS) against trinitrobenzene sulfonic acid (TNBS)-induced colitis was examined in rats. Rats were fed a HAS-free basal diet or, a 15% or 30% HAS supplemented diet for 10 d, and then received intracolonic TNBS to induce colitis and fed the respective diets for a further 8 d. HAS ingestion significantly protected colonic injuries as evidenced by lower colonic myeloperoxidase activity. Rats fed the HAS diet showed greater cecal short-chain fatty acid (SCFA) production than those fed the basal diet. Further, just before TNBS administration, HAS ingestion dose-dependently increased fecal and cecal mucin contents, and protein and nucleic acid contents in the colonic mucosa. HAS ingestion also reduced colonic permeability. The protective effect of HAS ingestion on TNBS-induced colitis is perhaps exerted through alterations in colonic mucosa, possibly due to cecal SCFA production.     

Effect of stress and immune stimulus on the pituitary-adrenal axis in gray rats selected for behavior

A comparison of effects of the restrain stress, and lipopolysaccharide and interleukin-2 treatment on pituitary-adrenal system of tame and aggressive rats, was examined. It was found that plasma ACTH and corticosterone levels in response to restrain stress and lipopolysaccharide treatment were significantly decreased in the tame rats compared to aggressive ones. By contrast, the maximum corticosterone level was the same in plasma of both groups after interleukin-2 treatment, although the time patterns of the response were different. Thus the selection of wild grey rats for tame behavior results in change of the response of the pituitary-adrenal axis to the immune stimulus. It is conceivable that the interaction between pituitary-adrenal axis and immune system also changes in tame rats.     

Effects of bilateral olfactory bulbectomy on the anterior pituitary corticotropic cell activity in male rats.

Bilateral olfactory bulbectomy (OB) has drastic biochemical and behavioral effects and is often associated with an increase in plasma corticosterone concentrations. This experiment examined the effects of OB on adrenocorticotropin (ACTH) and corticosterone release under basal and stress conditions and on proopiomelanocortin (POMC) gene expression. Bulbectomy potentiated hypophysal ACTH and adrenal corticosterone release induced by ether stress but had no effect on ACTH release under basal conditions, despite a significant increase of circulating corticosterone. POMC gene expression was stronger (+60%) in OB rats than in sham-operated rats. These results suggest that olfactory bulbectomy substantially altered the negative feed-back exerted by glucocorticoids on anterior pituitary corticotropic cells in the male rat.     

Dietary resistant starch alters the characteristics of colonic mucosa and exerts a protective effect on trinitrobenzene sulfonic acid-induced colitis in rats

The protective effect of a dietary high-amylose cornstarch (HAS) against trinitrobenzene sulfonic acid (TNBS)-induced colitis was examined in rats. Rats were fed a HAS-free basal diet or, a 15% or 30% HAS supplemented diet for 10 d, and then received intracolonic TNBS to induce colitis and fed the respective diets for a further 8 d. HAS ingestion significantly protected colonic injuries as evidenced by lower colonic myeloperoxidase activity. Rats fed the HAS diet showed greater cecal short-chain fatty acid (SCFA) production than those fed the basal diet. Further, just before TNBS administration, HAS ingestion dose-dependently increased fecal and cecal mucin contents, and protein and nucleic acid contents in the colonic mucosa. HAS ingestion also reduced colonic permeability. The protective effect of HAS ingestion on TNBS-induced colitis is perhaps exerted through alterations in colonic mucosa, possibly due to cecal SCFA production.     

Stress-induced changes of glucocorticoid receptor in rat liver.

The effect of corticosterone injection and of acute and repeated stress on rat liver cytosol glucocorticoid receptor was studied to ascertain whether corticosterone-induced glucocorticoid receptor (GR) regulation also takes place in intact animals as it does in adrenalectomized ones. Adult male rats were exposed to six different stressors (swimming, 10 mg/kg histamine i.p., 500 mU/kg vasopressin s.c., heat, immobilization and cold) acutely or three times daily for 18 days (repeated stress). Each of the stressors applied acutely provoked a pronounced increase of plasma corticosterone with subsequent induction of hepatic tyrosine aminotransferase activity. Depletion of cytosol receptor was however only noticed after swimming and histamine injection. On the other hand, sustained hypersecretion of corticosterone evoked by repeated stress significantly reduced the number of GR in rat liver cytosol without any change in Kd. It is concluded that in the presence of intact adrenal glands cytosol receptors are more resistant to corticosterone-induced depletion than in their absence. Further, repeated stress causes down-regulation of GR in the liver, most probably by sustained corticosterone secretion, yet the effect of other stress factors cannot be excluded.     

Chronic cold stress modulates the function of peritoneal macrophages in vivo

On day 7 of chronic cold stress, concentration of corticosterone in plasma was established to increase, zymosan-induced production of reactive oxygen species was activated, and IL-10 synthesis by macrophages was enhanced regardless of the opiate receptor blockade. Increase in the concentration of corticosterone was independent of the blockade of opioid receptors, whereas the zymosan-induced increase in the production of oxygen radicals and activation of the spontaneous production of IL-10 was blocked in mice by naloxone. Chronic cold stress had no effect on the production of IL-1β and TNF-α.