Biomedical subjects

A Armario

Publications and source records attributed to A Armario.

At least 91 records · Page 5Linked to original sources

PubMed1988

Metallothionein response to stress in rats: role in free radical scavenging.

The possibility that liver metallothionein (MT) can function as an antioxidant in vivo has been studied in the rat. It was found that the stress of food and water deprivation with or without physical immobilization consistently increased liver lipid peroxidation (LLP), suggesting that liver MT induction by stress might be related to the stress-induced LLP. This was supported by results with the lipid peroxidation promoter dimethyl sulfoxide (DMSO) and the natural antioxidant vitamin E. Whereas DMSO administration increased LLP levels in basal and stress situations, vitamin E decreased them. Liver MT levels were increased by DMSO in basal and stress situations, whereas they were decreased by vitamin E during stress. These in vivo results are consistent with an antioxidant role of liver MT suggested by previous in vitro results. However, liver MT preinduction by Zn treatment did not result in a lower MT response to stress. Instead a positive synergistic effect between Zn and stress appeared to be present. This result indicates that the mechanism of action of MT as antioxidant remains unclear.

Animals↗

PubMed1988

Evidence that the pituitary-adrenal axis does not cross-adapt to stressors: comparison to other physiological variables.

The effects of previous chronic immobilization stress on the physiological responses of male rats to a novel chronic stressor (shock) were studied. Previous chronic exposure to immobilization reduced adrenocorticotropin (ACTH) and lactate responses to acute immobilization stress without altering the response to a novel acute stressor (tail shock). When subjected to chronic tail shock, body weight inhibition caused by chronic shock was greater in the rats not previously exposed to chronic immobilization, which suggests that there is cross-adaptation between different stressors. However, adrenocorticotropin adaptation to chronic shock was impaired by previous chronic immobilization. These data indicate that the existence of cross-adaptation to stressors might depend on the variable measured, the central nervous system pathways controlling the pituitary-adrenal axis being, apparently, resistant to cross-adaptation. This lack of cross-adaptation at certain levels can assure the maintenance of an adequate response to unknown environmental stimuli.

Adaptation, Physiological↗

PubMed1988

Differences between pregnant and nulliparous rats in basal and stress levels of metallothionein.

The present experiment was designed to examine the influence of pregnancy on basal and stress levels of serum and liver metallothionein (MT). Eighteen-day pregnant rats showed higher serum MT levels and lower liver MT levels than nulliparous rats, suggesting that a great MT mobilization from the liver into the serum was present in the former rats. Serum MT levels were not changed by either restraint or starvation. It is unlikely that the lower liver MT levels showed by pregnant rats were due to competition by progesterone for glucocorticoid receptors, as previously suggested, since the corticosterone/progesterone ratio was unchanged in pregnant rats. Liver MT response to food and water deprivation with or without restraint was somewhat different in nulliparous and pregnant rats. Thus, food and water deprivation for 24 h caused higher liver MT induction in pregnant than in nulliparous rats. When food and water deprivation was accompanied by restraint stress a further increase in liver MT was observed in nulliparous but not in pregnant rats. This suggests that food and water deprivation may be a more severe stress in pregnant rats because of the additional demands of the growing fetuses. Fetal liver MT was increased by restraint stress but not by food and water deprivation. The role of Zn influx into the liver is discussed.

Animals↗

PubMed1987

Long-lasting effects of chronic chlorimipramine treatment of rats on exploratory activity on a hole-board, and on immobility in the forced swimming test.

The study concerned the effects of acute and chronic clomipramine administration to male rats on exploratory activity in a novel environment (hole-board) and on immobility in the forced swimming test. Acute clomipramine administration did not alter either exploratory activity on a hole-board as measured 3 or 20 h after drug administration, or immobility in the forced swimming test as measured 20 h after drug administration. Approximately 20 h after the last injection of clomipramine, the rats chronically treated with the drug showed reduced exploratory activity on the hole-board. In contrast, chronic clomipramine treatment significantly increased the activity in the forced swimming test. The effects of the drug on exploratory and forced swimming activities persisted for 14 days after the cessation of clomipramine administration. These data indicate that chronic clomipramine administration exerted profound and long-lasting effects on central nervous system function. The long-lasting action of the drug on behaviour in the forced swimming test might explain the long-term beneficial effect of antidepressant drugs in counteracting behavioral depression.

Animals↗

PubMed1987

Tricyclic antidepressants activate the pituitary-adrenal axis in the rat. Tolerance to repeated drug administration.

The effects of acute chronic administration of tricyclic antidepressants on the pituitary-adrenal axis were studied in adult male rats. Acute administration of desipramine, imipramine and chlorimipramine activated the pituitary-adrenal axis. The effect of imipramine was found to be of short duration with a significant increase at 30 and 60 min after the administration of the drug and a return to baseline levels at 180 min. The effect of imipramine was dose-dependent. Twenty hours after the last drug administration rats chronically injected with chlorimipramine showed normal basal and saline-induced levels of corticosterone. However the response of these rats to an acute dose of chlorimipramine was significantly lower than that of drug-naive rats, indicating tolerance to the drug. The mechanisms involved in the activation of the pituitary-adrenal axis caused by antidepressants and the tolerance to repeated drug administration are still unknown.

Adrenocorticotropic Hormone↗

PubMed1987

The effects of chronic stress on corticosterone, GH and TSH response to morphine administration.

The effects of a chronic stress model in which several acute stressors were applied on a random basis on corticosterone, growth hormone (GH) and thyroid stimulating hormone (TSH) responses to morphine administration were studied in adult male rats. Chronic stress resulted in lower corticosterone response to the drug. In contrast, GH response to morphine was enhanced in the former animals and TSH response remained unchanged. The physiological role of changes in hormone response to opiates remains to be established, but the present results suggest that central opioid pathways involved in the neuroendocrine control of the anterior pituitary did not respond homogeneously to chronic stress.

Adrenal Cortex↗

PubMed1987

Interaction between chronic stress and clomipramine treatment in rats. Effects on exploratory activity, behavioral despair, and pituitary-adrenal function.

The interaction between the effects of chronic electrical tail shock and clomipramine (CMI) on exploratory activity, behavioral despair and pituitary-adrenal function was studied in adult male rats. Both CMI and shock administered alone significantly reduced exploratory activity in a novel environment (holeboard). Neither interaction nor additive effects were observed when the two treatments were combined. In contrast, chronic shock increased the immobility in the forced swimming test (behavioral despair) and this effect was completely prevented by concomitant CMI administration. Pituitary-adrenal function was not significantly influenced by any of the treatments. The results indicate that: (a) chronic CMI treatment prevented some but not all behavioral changes caused by chronic shock, and (b) no interaction with basal and stress levels of pituitary-adrenal hormones was observed.

Adrenocorticotropic Hormone↗

PubMed1987

Age-dependent effects of acute and chronic intermittent stresses on serum metallothionein.

Prepuberal and adult male rats were chronically stressed for a month with several acute stressors in a random schedule. Some of the animals were killed approximately 20 hours after the last stress session without any additional stress. Other animals from both control and chronic stress groups were subjected to an acute restraint stress for 15 min before being killed. While chronic stress did not alter hepatic metallothionein (MT) either in prepuberal or in adult rats, this treatment significantly increased serum MT levels in young but not in adult rats. Likewise, 15 min of restraint stress increased serum MT levels in young rats only, regardless of whether they were control or chronically stressed rats. The present data indicate that acute and chronic stressors may alter serum MT in an age-dependent fashion.

Acute Disease↗

PubMed1987

Chronic stress depresses exploratory activity and behavioral performance in the forced swimming test without altering ACTH response to a novel acute stressor.

The present study investigated the effects of chronic stress on some behavioral and endocrine variables in adult male rats. The variables were always measured the day that followed the stress session to chronically stressed rats. Two stress models were used: chronic shock (CS), and a combination of various stressors randomly chosen each day (CV). Chronic but not acute exposure to the stressors resulted in decreased exploratory activity in the holeboard. Likewise, only chronic exposure to shock or variable stressors resulted in increased immobility in the Porsolt's test. Taken together these results suggest that changes in exploratory and forced swimming activities might be affected by chronic stress. In contrast, neither CS nor CV rats showed altered basal or stress-induced levels of ACTH which suggests that the activity of the axis was unchanged. Although the present data indicate that chronic stress caused behavioral abnormalities closely related to that expected to take place in some type of depressive disorders, endocrine data are not in good agreement with those occurring in depression.

Adrenocorticotropic Hormone↗

PubMed1987

Previous chronic ACTH administration does not protect against the effects of acute or chronic stress in male rats.

The effect of previous chronic ACTH administration on the physiological response to acute and chronic immobilization stress was studied in adult male rats. Chronic ACTH administration slightly reduced food intake and drastically inhibited body weight gain. Serum corticosterone levels were similar in saline- and ACTH-treated rats twenty hours after the last administration. However, the corticosterone response to 1 hr immobilization was greatly reduced by previous ACTH administration. When the exposure to the stressor was prolonged up to 18 hours, the corticosterone response was similar in saline, and ACTH-treated rats. While body weight loss caused by starvation and acute stress was lower in ACTH-treated rats, stomach ulceration was greater in the latter animals. Although ACTH-treated rats showed higher body weight gain than saline-treated animals during chronic immobilization, this was probably due to catch-up growth as food intake inhibition caused by the stressor was similar in the two groups. Pituitary-adrenal adaptation to the repeated stressor was the same in saline- and ACTH-treated rats. Therefore, the effects of previous ACTH treated on the physiological response to either acute or chronic stress appear to be mixed, depending on the variable studied.

Adrenal Glands↗

PubMed1987

Effect of Cd administration on the pituitary-adrenal axis.

The possibility that Cd administration could activate the pituitary-adrenal axis has been studied. It was found that acute administration of Cd strongly increased serum corticosterone levels. Adrenocortical activation correlated well with serum Cd levels, suggesting that adrenal activation was dependent on the presence of the metal in the blood. In addition, our data clearly demonstrate that increased corticosterone secretion caused by Cd was, at least in part, mediated by adrenocorticotropin release. Therefore, it appears that Cd might cause similar endocrine and metabolic changes as classical stress agents.

Adrenocorticotropic Hormone↗

PubMed1987

Chronic stress alters pituitary-adrenal function in prepubertal male rats.

The effect of exposure to chronic stress on the pituitary-adrenal axis was studied in prepubertal rats. The chronic stress consisted of exposing the animals 6 days a week for 32 days to one stressor randomly chosen among several each day. Chronic stress did not alter either food intake or body weight gain. However, it was stressful for the rats, as they had increased adrenal weights. Chronically stressed rats showed normal pituitary-adrenal basal activity and normal ACTH responses to a novel, acutely applied stressor. However, this treatment resulted in higher corticosterone response to an acute stressor, as a consequence of enhanced adrenocortical response to ACTH. In addition, chronic stress induced increasing sensitivity of the adrenal to the inhibitory action of dexamethasone. Exploratory activity and defecation rate in a novel environment were not affected by the chronic stress. All these data indicate that behavioral and endocrine changes induced by chronic stress were somewhat different from those previously found in adult rats. Prepubertal rats appear to be less sensitive than adult rats to the chronic stress we used.

Adrenal Glands↗

PubMed1987

The effects of chronic intermittent stress on basal and acute stress levels of TSH and GH, and their response to hypothalamic regulatory factors in the rat.

The effect of chronic stress on basal and stress-induced alterations of TSH and GH was studied in adult male rats. Chronically stressed rats were subjected 6 days per week for 4 weeks to several acute stressors including saline injections, noise, ether and forced swimming. Each day, one stressor was chosen randomly. Twenty hr after the last stress session, basal levels of TSH were normal or increased, with no altered pituitary response to TRH. In contrast, the TSH rise induced by acute stress was blunted in chronically stressed rats. Chronic stress resulted in lower basal and acute stress levels of GH. These modifications were probably due to changes in the release of hypothalamic regulatory hormones, because no evidence for altered TSH response to TRH, and GH response either to GHRH or to somatostatin, was found. Some abnormal responses of GH to TRH and of TSH to GHRH were observed in chronically stressed rats. These data indicate that this type of chronic stress induced significant changes in basal and acute stress levels of GH and TSH in the rat.

Animals↗

PubMed1987

Crowding-induced changes in basal and stress levels of thyrotropin and somatotropin in male rats.

The effects of crowding on thyrotropin (TSH) and somatotropin (GH) secretion were studied in two-month-old male rats. Crowded rats (9-10 per cage) showed lower serum GH levels than controls (3 per cage). Likewise, serum GH was lower in crowded rats after acute exposure to stress. However, percentage inhibition of GH secretion induced by acute stress was similar in crowded and control rats. Crowding reduced the TSH response to acute stress. The results found with the administration of hypothalamic regulatory factors suggest that the impaired GH and TSH secretion observed in crowded rats was not likely to be at the pituitary level. Therefore, altered neuroendocrine control of GH and TSH secretion appears to exist in crowded rats. Preliminary results obtained in rats crowded from weaning to adulthood suggest that food restriction only partially accounts for the changes observed in crowded rats.

Animals↗

PubMed1987

Chronic food restriction and the circadian rhythms of pituitary-adrenal hormones, growth hormone and thyroid-stimulating hormone.

Adult male Sprague-Dawley rats were subjected to food restriction so that they ate 65% of food ingested by control rats. While control rats had free access to food over the 24-hour period, food-restricted rats were provided with food daily at 10 a.m. The experimental period lasted for 34 days. On day 35, rats from both experimental groups were killed at 08.00, 11.00, 14.00, 24.00 and 02.00 h. Food restriction modified the circadian rhythms of ACTH and corticosterone. In addition, total circulating corticosterone throughout the day was higher in food-restricted than in control rats. In contrast, food restriction resulted in depressed secretion of thyroid-stimulating hormone and growth hormone. The results indicate that time of food availability entrained circadian corticosterone rhythm but not thyroid-stimulating hormone and growth hormone rhythms.

Adrenal Glands↗

PubMed1987

Differences in prolactin and LH responses to acute stress between peripuberal and adult male rats.

Pituitary-adrenal, pituitary-gonadal and prolactin responses to acute stress (restraint) were studied in peripuberal and adult male rats. The pituitary-adrenal response to restraint stress did not differ in peripuberal and adult rats. Prolactin increase during stress was less marked in peripuberal animals. While an increase in LH during stress was observed in adult rats, peripuberal animals did not respond to stress. Testosterone levels were also lower in peripuberal than in adult rats. Diminished LH and prolactin responses to stress in peripuberal rats did not appear to be due either to increased pituitary-adrenal activity or to altered pituitary responsiveness to LHRH and dopamine respectively. Peripuberal rats were also more sensitive to the action of morphine on LH and prolactin release than were adult rats, suggesting that endogenous opioids may be involved in the LH and prolactin responses to acute stress. Differences in the maturation of central mechanisms rather than in pituitary response appear to be responsible for the differing responses to acute stress.

Acute Disease↗

PubMed1987

Sex and restraint stress differences in rat metallothionein and Zn levels.

Sex differences in serum and liver metallothionein (MT) levels were studied in adult male and female rats. Whereas it was found that female rats had higher hepatic MT levels than male rats in basal, unstressed conditions, no significant differences were found in serum MT levels. Restraint stress increased both serum and liver MT in both sexes. The increase in serum MT was greater in male than in female rats, whereas no significant differences between sexes were found in liver MT content after restraint stress. It is suggested that MT regulation might be sex-dependent and that MT might play some extrahepatic function during stress.

Analysis of Variance↗

PubMed1987

The role of catecholamines and glucagon on serum and liver metallothionein response to restraint stress.

The role of glucagon and catecholamines on serum and liver metallothionein (MT) concentrations in basal and stress conditions has been studied. Glucagon showed no effect on serum MT either in basal (unstressed) or stress (20 hours of restraint) conditions. In contrast, glucagon administration increased both unstressed and stressed levels of liver MT. No effect of the alpha + beta-catecholamine blocker labetalol on serum MT levels was observed in unstressed rats. However, the administration of labetalol abolished the increase in serum MT levels caused by stress. These data suggest that catecholamines might be involved in serum MT regulation during stress, while they might not be important in the maintenance of basal serum MT levels. Finally, no significant effect of adrenergic blockade was found on basal and stress levels MT, in agreement with previous data from this laboratory.

Animals↗