Changes In Plasma Corticosterone Levels Research Articles

The effects of acclimation temperature on pituitary and plasma beta-endorphin in rats at 32.5°C

1. Endocrine and thermoregulatory responses were studied in male rats exposed to heat (32,5 ± 0.1 °C) from acclimation temperatures of either 24.5 ± 0.1°C or 29.2 ± 0.1 °C. 2. After 1 hr in the heat, evaporative water loss and tail skin temperature changes in the 24.5°C acclimated rats were greater than in the 29.2°C acclimated rats; both groups displayed similar changes in metabolic rate and rectal temperature. 3. At the respective acclimation temperatures, 29.2°C rats displayed lowered plasma thyroid hormones, elevated beta-endorphin-like immunoreactivity (β -END-LI) in the plasma, neurointermediate and anterior lobes of the pituitary gland, and no change in plasma corticosterone levels compared to 24.5°C rats. 4. After exposure to 32.5°C for 1 hr, both groups of rats maintained similar plasma corticosterone levels; however, only the 24.5°C group increased plasma thyroxine and β-END-LI. 5. These data suggest that beta-endophin may be involved in body temperature regulation during acclimation to elevated environmental temperatures.

The effect of Althesin on plasma corticosterone levels

Althesin in doses which produced anethesia (4 and 6 ml kg −1, i.p.) produced biphasic changes in plasma corticosterone levels. Plasma corticosterone showed an increase (p < 0.05) due to the stress of injection but returned to basal levels by 30 min. Subsequent to the anesthetic effect (approximately 30 min) corticosterone levels increased markedly (p < 0.01). Althesin's effectiveness showed time of day effects, i.e., Althesian was more effective in the A.M. Rats given 6 ml kg −1 Althesian showed graded plasma corticosterone responses to stresses of varying intensity. Blood withdrawal and surgical stress evoked significant increases in plasma corticosterone but a 2-min holding stress had no effect on plasma corticosterone levels. Instrumented rats receiving supplemental injections (i.p.) presented patterns of plasma corticosterone which were different from those receiving supplemetal infusions (i.a). Whereas plasma corticosterone levels of rats receiving the continuous infusion of Althesin remained relatively constant, corticosterone levels of those which received supplemental injections tended to increase. Collectively, these data suggest that Althesins usefulness as an experimental anesthetic is limited to those studies which are not compromised by stress-induced pituitary-adrenal activity.

Cold acclimation of obese ( [formula omitted]) mice: Effects on skeletal muscle and bone

Obese ( ob ob ) and lean mice at 4 weeks of age were housed at 23 °C or 14 °C for 4 or 8 weeks to determine effects of acclimation to mild cold on the growth of skeletal muscle, bone, and fat. Body weights at 12 weeks of age averaged 48 ± 0.6 g and 27 ± 1.9 g for obese mice housed at 23 °C and 14 °C and 29 ± 0.5 g and 26 ± 0.6 g for lean mice housed at 23 °C and 14 °C, respectively. At 23 °C, muscle weights of obese mice were approximately 60% of those in lean mice. Muscles of obese mice did not grow during the first 4 weeks at 14 °C (4 to 8 weeks of age) but did show a small gain during the second 4 weeks (9 to 12 weeks of age) at 14 °C. As a result, by the end of 8 weeks at 14 °C, muscles of obese mice weighed only 35% to 45% as much as muscles of lean mice. Growth of the tibia and femur followed the same pattern as the muscles. Obese mice housed at 23 °C from 4 to 12 weeks of age contained about six times as much fat as lean mice at this age. Although exposure to 14 °C for 8 weeks depressed the accumulation of fat in obese mice, they still contained approximately three times the percentage body fat as lean counterparts. The concentrations of corticosterone and insulin in plasma of 8 week old obese mice housed at 23 °C were two to four times and 20 times higher, respectively, than in lean mice; after 4 weeks at 14 °C the difference for corticosterone was even greater, ie, five to ten times higher in 8 week old obese, whereas the concentration of insulin in plasma of obese mice was only seven times higher than in lean mice at 14 °C. The marked reduction in skeletal muscle and bone growth observed in young obese mice as a result of cold acclimation permitted them to decrease body weight gain to equal that of lean mice without a concomitant reduction in their high percentage of body fat. These cold-induced reductions in muscle and bone growth in obese mice may have been facilitated by the observed changes in plasma corticosterone levels.

Differential plasma corticosterone responses to hippocampal stimulation.

The effect of limbic forebrain stimulation on pituitary-adrenal function was assessed by evaluating plasma corticosterone obtained prior to and following sham or electrical stimulation of urethane (1.20 g/kg) anesthetized female rats. Cortical electroencephalogram (EEG), electrocardiogram (ECG), heart rate (HR), mean arterial blood pressure (MAP), and respiration were routinely monitored. Timed blood samples (0.25 ml) were obtained from a catheterized femoral artery. The HR (Bts/min), MAP (mm of Hg), and corticosterone levels (microgram/dl) for 7 non-stimulated rats averaged over 6 sampling periods were 385 +/- 19,95 +/- 6, and 70.3 +/- 5.8 respectively. In electrically or sham stimulated rats, blood samples were taken just prior to stimulation (biphasic square waves, 100 microA, 50 or 60 Hz, 1 ms, 1 s on/1 s off for 15 or 30 min) and 5, 10, 15, and 30 min after initiation of stimulation. Significant changes in plasma corticosterone levels were obtained following stimulation of hippocampal and amygdaloid areas. In contrast, no change in corticosterone concentration was observed following stimulation of cortex, corpus callosum, fornix and a variety of other CNS areas. Detailed analysis of hippocampal influence on urethane stimulated plasma corticosterone levels showed increased plasma corticosterone levels following stimulation of CA1. In contrast, stimulation of CA3, dentate (includes CA4) and the subiculum produced significant decreases in plasma corticosterone levels. No change in corticosterone levels was observed following sham stimulation. Collectively, these data indicate that consideration must be given to the possibility that differential neuroendocrine regulatory mechanisms reside within various limbic forebrain complexes and that electrical stimulation of limbic forebrain sites of urethane anesthetized rats may provide information regarding sites inhibitory to pituitary-adrenal activity.

Effect of whole body vibration on the rat brain content of serotonin and plasma corticosterone.

To investigate the effects of whole body vibration on the central nervous system, rats were exposed to various whole body vibrations and changes in whole brain levels of Serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were then determined. Changes in plasma corticosterone levels were also determined and related to the changes in the whole brain levels of 5-HT and 5-HIAA. The dose-related changes in the 5-HT and 5-HIAA levels were observed as acceleration increased from 0.4G to 5.0G. Changes in vibration frequency also affected the 5-HT and 5-HIAA levels of brain: they were significantly elevated at a frequency of 20 Hz (P less than 0.05). Plasma corticosterone levels increased as acceleration increased from 0.4G to 5.0G. As the vibration frequency was changed from 5 Hz to 30 Hz, plasma corticosterone levels also rose significantly (P less than 0.05) but the extent of elevation was approximately the same at each frequency. The correlation between brain 5-HT and plasma corticosterone levels with increasing acceleration (r = 0.93, P less than 0.01) was significant.

Changes in plasma corticosterone levels of inbred mice after stress

Changes in plasma corticosterone levels of inbred mice after stress

Effects of hypothalamic deafferentations on adrenocortical responses in the rat following hippocampal stimulation.

Adrenocortical responses, as expressed by changes in plasma corticosterone levels, following ether stress and dorsal hippocampal stimulation, were studied in intact rats and in rats with complete, anterior of posterior hypothalamic deafferentations. Ether stress produced normal responses in all experimental groups. In the three groups with hypothalamic deafferentations, the adrenocortical response following hippocampal stimulation was completely blocked, when compared to intact animals. The results suggest that the hippocampal signal enters the hypothalamus anteriorly, but that caudal propagation and posterior re-entry into the hypothalamus are also essential for the adrenocortical activation by the hippocampus.

Levels and subcellular distribution of endogenous corticosterone in rat liver during development

The concentration of corticosterone in liver homogenates, liver cytosol and purified nuclear fractions, and in plasma of fetal, newborn, immature and adult rats has been measured by radioimmunoassay. Highest plasma corticosterone levels were found in fetal rats, decreasing close to the levels observed in the adrenalectomized rat by the 6th day of postnatal life followed by a rise in the adult rat. The concentration of corticosterone in liver during development paralleled the plasma levels, the liver to plasma corticosterone ratio ranging between 0.09 and 0.17 suggesting that the corticosterone retained by the tissue is related to the unbound fraction of the hormone in plasma.Both plasma and tissue corticosterone levels declined after adrenalectomy and they were elevated after ether stress. Fractionation of liver homogenates showed that the major fraction of liver corticosterone is localized in the cytosol. Purified liver nuclei contained between 9 and 16% of the total liver corticosterone. The amount of corticosterone in the nuclei seems to be related to the plasma and tissue hormone levels rather than the concentration of cytoplasmic glucocorticoid receptors. Since most of the nuclear corticosterone appears to be bound to receptors, it has been calculated that close to 60% of the cellular receptors in fetal liver are localized in the nucleus. In adult rat liver, only about 10% of the cellular receptors appear to be associated with nuclei. Changes in the concentration of glucocorticoid receptors in liver during development and after adrenalectomy are inversely related to changes in plasma corticosterone levels. It is suggested that corticosterone may regulate the levels of its own receptors in liver.

Adrenocortical responses to olfactory stimulation in rats with hypothalamic islands.

Department of Neurology, Hadassah University Hospital, Jerusalem, Israel (Received 27 October 1975) There exists both anatomical and electrophysiological evidence that olfactory pathways project to the hypothalamus (Scott & Pfaffmann, 1967; Scott & Chafin, 1975). Hypothalamic island preparations were used to differentiate between 'systemic' stresses which produced normal adrenocortical responses and 'neurogenic' stresses which caused a reduced adrenal discharge (Feldman, Conforti, Chowers & Davidson, 1970; Feldman, Conforti & Chowers, 1975). This paper describes the role of the hypothalamic neural connexions in the mediation of the adrenocortical response following olfactory stimulation. Experiments were performed on male albino rats of the Hebrew University strain weighing approximately 250 g. Adrenocortical responses to ether stress and to olfactory stimulation, as determined by changes in plasma corticosterone levels (Click, von Redlich & Levine, 1964), were studied in 33 intact animals and in 33 rats with hypothalamic islands (Halasz & Pupp, 1965). The protocol consisted of submitting

Interactions of self-stimulation behavior and some humoral factors

This chapter focuses on the interactions of self-stimulation behavior and some humoral factors. Changes in plasma corticosterone levels, hypothalamic and mesencephalic serotonin contents, and self-stimulation (SS) behavior are investigated in rats after electrical stimulation (ES) or SS of the medial forebrain bundle (MFB) region, and following injection of cholinergic drugs into the nucleus raphe dorsalis or the lateral ventricle. The results indicate that both serotoninergic and cholinergic systems are important in the organization of SS behavior. Cholinergic drugs injected into the lateral ventricle increased the plasma corticosterone level and decreased the hypothalamic and the mesencephalic serotonin contents, and the rate of SS.

Effect of stress and environmental temperature on adrenal function in Rana esculenta.

SUMMARY The effect of immobilization for 60 min on the adrenal activity of frogs (Rana esculenta) was studied by measuring corticosterone in plasma and corticosterone and catecholamines in adrenorenal homogenates. An increase in plasma corticosterone and in noradrenaline in the adrenorenal homogenate was observed after immobilization for 5 min and there was further increase after prolonged immobilization. However, there was no change throughout the period of immobilization in the corticosterone and adrenaline content of the adrenorenal homogenates. When frogs were exposed to various environmental temperatures the resting plasma corticosterone level did not change at temperatures below 20 °C, but rose significantly at temperatures above 20 °C. No increase in plasma corticosterone concentration occurred at 1 °C after corticotrophin (ACTH) administration. At higher temperatures (up to 30 °C) a significant correlation was found between plasma corticosterone levels after ACTH administration and environmental temperature. No further increase in plasma corticosterone took place at temperatures up to 40 °C. The results indicate a rapid activation of both the interrenal and chromaffin components of the adrenal gland in Rana esculenta when subjected to this type of stress. Changes in plasma corticosterone levels resulting from changes in environmental temperature may be either an expression of specific changes in steroidogenesis of the adrenals, or of the entire metabolic activity of the organism.

Changes in plasma corticosterone levels of the young rabbit after injury.

SUMMARY The changes in plasma corticosterone levels and sudanophilia of the adrenal cortex after a 3-h period of bilateral hind-limb ischaemia in a thermoneutral environment were studied in 1–2, 12 and 38- to 42-day-old rabbits. There was a significant increase in plasma corticosterone accompanied by a decrease in sudanophilia of the adrenal cortex after tourniquet removal at all ages. The results indicate that there are sufficient steroids present at all ages studied for the expression of the various responses elicited by injury.

Studies on the role of catecholamines as regulators of tyrosine aminotransferase

It has been suggested that catecholamines are involved in the control of tyrosine aminotransferase activity. We have studied the effects of drugs which produce adrenergic blockade and catecholamine depletion on the activity of tyrosine aminotransferase (TAT) in rat liver. Phentolamine was found to increase TAT activity while phenoxybenzamine and propranolol had no effect. Of the depleting agents tested reserpine, guanethidine and α-methyl-para-tyrosine increased TAT activity while α-methyl-meta-tyrosine had no effect. All compounds which increased TAT activity also increase the plasma corticosterone concentration; α-methyl-para-tyrosine also increased slightly the enzyme activity in adrenalectomized rats. Thus, TAT activity is influenced by the changes in plasma corticosterone levels which these compounds produced, rather than their adrenergic blocking or catecholamine depleting effects. The response to α-methyl-para-tyrosine in adrenalectomized animals suggests that some additional mechanism is also involved.

Effects of rapid eye movement (REM) sleep deprivation on shock-induced fighting☆☆☆

Abstract The effects of REM sleep deprivation on shock-induced fighting behavior in rats were studied in three experiments. The experimental animals were selectively deprived of REM sleep by maintaining them on a small pedestal surrounded by water. One control group was maintained under similar conditions except that REM sleep was permitted to occur, while a second control group was conventionally housed. Fighting behavior was elicited by administering a train of brief electric shock pulses at five intensities to pairs of rats. In Experiment 1, fighting behavior was studied before, during, and after REM sleep deprivation. Experiment 2 replicated the first study except that fighting was not studied during the treatment period. REM sleep deprived animals showed dramatic increases in fighting frequency which persisted even after prolonged sleep recovery. In Experiment 3, the experimental group had a history of four previous cycles of REM sleep deprivation and recovery before fighting behavior was studied. The animals previously deprived of REM sleep fought significantly more than their controls. In Experiments 4 and 5 the adrenocortical stress response was examined in REM sleep deprived and control animals. Results indicated statistically significant but small changes in plasma corticosterone levels as a result of REM sleep deprivation.

Genetic Variation in Responses to Repeated Administrations of ACTH and Hydrocortisone in Immature Chickens

BEFORE one considers the relationships between responses to exogenous ACTH or glucocorticoid administration and responses to environmental stimuli, it is important to consider whether birds from varying genetic backgrounds respond similarly to these exogenous materials.Thiessen and Nealy (1962), using eosinophil count and adrenal weight as response criteria to handling stress, reported that the pattern of response for one of five inbred strains of mice could not be used to predict the pattern for the others. Highly significant differences in changes of plasma corticosterone levels resulting from electric shock treatments were found among four inbred mouse strains by Levine and Treiman (1964).Genetic differences in thiouracil-induced hypothyroidism (El-Ibiary and Shaffner, 1951; Shaklee and Shaffner, 1955), and in assay sensitivity to gonadotropins (Siegel and Siegel, 1964a, b) have been observed; however, little has been reported concerning genetic influences upon the response of the avian pituitary-adrenal cortical system to exogenous hormone stimulation… .