Plasma Corticosterone In Rats Research Articles

Role of brain nicotinic acetylcholine receptor in centrally administered corticotropin-releasing factor-induced elevation of plasma corticosterone in rats

The present study was undertaken to clarify the central mechanisms involved in the intracerebroventricularly administered corticotropin-releasing factor-induced elevation of plasma corticosterone in urethane- and α-chloralose-anesthetized rats using microdialysis and immunohistochemical techniques. When corticotropin-releasing factor was given at 0.5, 1.5, and 3.0 nmol/animal intracerebroventricularly, it dose-dependently increased noradrenaline release but not adrenaline release in the hypothalamic paraventricular nucleus. The 1.5 nmol/animal dose of corticotropin-releasing factor-induced noradrenaline release was attenuated by CP-154,526 (butyl-ethyl-{2,5-dimethyl-7-(2,4,6trimethylphenyl)-7 H-pyrrolo[2,3- d]pyrimidin-4-yl}amine), a selective corticotropin-releasing factor receptor 1 antagonist, at 1.3 μmol/animal, intracerebroventricularly, and was also abolished by phentolamine at 0.66 μmol/animal, intracerebroventricularly. In addition, the corticotropin-releasing factor-induced elevation of noradrenaline release in the hypothalamic paraventricular nucleus and plasma corticosterone were abolished by hexamethonium, a non-selective nicotinic acetylcholine receptor antagonist, at 1.8 μmol/animal, intracerebroventricularly, and α-conotoxin MII, a potent α 3β 2 nicotinic acetylcholine receptor antagonist, at 30 nmol/animal, i.c.v. Corticotropin-releasing factor at 1.5 nmol/animal, i.c.v. evoked a significant expression of Fos, an immediate-early transcription factor in neurons, on the dopamine-β-hydroxylase-containing neurons and α 3 nicotinic acetylcholine receptor subunit-expressing neurons in the locus coeruleus, but not in the medullary A 1 and A 2 regions containing noradrenergic neurons. These results suggest that centrally administered corticotrophin-releasing factor elevates plasma corticosterone by the corticotropin-releasing factor 1 receptor and α 3 subunit-containing nicotinic acetylcholine receptor (probably α 3β 2 nicotinic acetylcholine receptor) mediated activation of the locus coeruleus noradrenergic neurons projecting to the paraventricular nucleus in rats.

Quantification of dexamethasone and corticosterone in rat biofluids and fetal tissue using highly sensitive analytical methods: assay validation and application to a pharmacokinetic study

A sensitive, specific, accurate and precise LC/MS/MS method was developed for the simultaneous measurement of dexamethasone and corticosterone in rat plasma. The method was extended to dexamethasone analysis in rat plasma ultrafiltrate and fetal tissues. Samples were processed using SPE involving Oasis HLB cartridges, which offered complete extraction recovery for the analytes. Samples were subsequently analyzed using LC/MS/MS. A structurally related corticosteroid, prednisolone, was used as the internal standard. Using a 500 microL plasma sample, limits of quantification of 0.2 and 2.0 ng/mL were achievable for dexamethasone and corticosterone. This level of sensitivity allowed characterization of maternal/fetal dexamethasone profiles after administration of multiple doses of dexamethasone sodium phosphate to rats. However, this sensitivity was not satisfactory for corticosterone during pharmacokinetic studies involving dexamethasone due to its strong adrenosuppressive effect. This led us to investigate the suitability of a commercially available radioimmunoassay kit, which through extensive testing and minor modifications was found to offer extremely sensitive, specific, accurate and precise analysis of corticosterone. Knowledge of the steroid profiles captured using these highly sensitive analytical tools may potentially help in the optimization of corticosteroid therapy during pregnancy.

Effect of chronic crowding on plasma corticosterone in rats with genetic predisposition to hypertension

Effect of chronic crowding on plasma corticosterone in rats with genetic predisposition to hypertension

Effect of Bacopa monniera on stress induced changes in plasma corticosterone and brain monoamines in rats

Bacopa monniera (BM) is well known for its neuropharmacological effects. Our previous studies indicated the adaptogenic effect of standardized extract of BM in various stress models. In the present study, effect of BM was evaluated on acute stress (AS) and chronic unpredictable stress (CUS) induced changes in plasma corticosterone and monoamines-noradrenaline (NA), dopamine (DA) and serotonin (5-HT) in cortex and hippocampus regions of brain in rats. Panax root powder ( Panax quinquefolium) was taken as standard. Subjecting animals to AS (immobilization for 150 min once only) and CUS (different stressors for 7 days) resulted in significant elevation in plasma corticosterone levels, which was significantly countered by treatment with BM at a dose of 40 and 80 mg/kg p.o. similar to the effects of Panax quinquefolium (PQ) at 100 mg/kg p.o. AS exposure significantly increased the levels of 5-HT and decreased NA content in both the brain regions while DA content was significantly increased in cortex and decreased in hippocampus regions. In CUS regimen, levels of NA, DA and 5-HT were significantly depleted in cortex and hippocampus regions of brain. Treatment with BM (40 and 80 mg/kg) attenuated the stress induced changes in levels of 5-HT and DA in cortex and hippocampus regions but was ineffective in normalizing the NA levels in AS model, whereas PQ treatment significantly reverted back the effects of stress. In CUS model, pretreatment with BM and PQ significantly elevated the levels of NA, DA and 5-HT levels in cortex and levels of NA and 5-HT in hippocampus regions. Hence, our study indicates that the adaptogenic activity of BM might be due to the normalization of stress induced alteration in plasma corticosterone and levels of monoamines like NA, 5-HT and DA in cortex and hippocampus regions of the brain, which are more vulnerable to stressful conditions analogous to the effects of PQ.

Regulation of the HPA axis by alpha 2 adrenoceptors

The hypothalamic-pituitary-adrenal (HPA) axis is regulated by numerous neurotransmitters, including central norepinephrine (NE), which exerts a stimulatory role on the HPA axis. There are numerous adrenoceptors (AR) subtypes involved in the regulation of the effects on NE, including 3 subtypes of alpha (α)2 ARS –α2A, α2B and α2C. While no evidence exists for a specific role of α2B ARs in regulation of central NE release, α2A and α2C ARs exist as presynaptic autoreceptors mediating NE neurotransmission. We investigated the role of the non-selective α2 antagonists RX821002 and idazoxan, a selective α2A antagonist BRL 44408 and a selective α2C antagonist OPC 28326 in blocking increases in rat plasma corticosterone levels produced by the α2 AR agonists clonidine and guanfacine. Corticosterone levels were increased 1 hour after systemic administration of both clonidine and guanfacine, which were dose-dependently blocked by both selective and non-selective α2 AR antagonists. These data suggest that both α2A and α2C ARs regulate the effects of NE on the HPA axis. Further studies on the in vivo effects of α2A and α2C ARs are needed to elucidate the functional activity of α2 ARs.

Cannabinoid CB 1 receptor antagonism modulates plasma corticosterone in rodents

Although the involvement of cannabinoids and the endogenous cannabinoid system in the regulation of the hypothalamo–pituitary–adrenal axis in rodents is well documented, the precise role played by the cannabinoid type one (CB 1) receptor in this effect has not been fully elucidated. Consequently, we investigated the role of CB 1 receptor in modulating plasma corticosterone concentrations through use of the potent and selective CB 1 receptor antagonist SR141716A and CB 1 receptor knockout mice. Rats were administered SR141716A (0.1, 0.3, and 1 mg/kg, i.v.) and blood was sampled at 0, 15, 60, 90 and 120 min postinjection. SR141716A dose- and time-dependently increased plasma corticosterone levels and maximum effects were obtained with the 1 mg/kg dose 60 min postinjection. In mice, SR141716A (0.1, 0.3, 1, 3, and 10 mg/kg, i.p.) also induced a dose-dependent rise in corticosterone levels 60 min postinjection; this rise reached plateau levels with the 0.3–1 mg/kg doses. The stimulatory effect of SR141716A (1 mg/kg, i.p.) on plasma corticosterone 60 min postinjection was abolished in the CB 1 receptor knockout mice, which did not show any difference in basal corticosterone levels as compared to their wild-type controls. Finally, the stimulatory effects of SR141716A (10 mg/kg, i.p.) on plasma corticosterone 60 min postinjection were retained after subchronic dosing (5 days, once daily) in mice. The present results indicate that SR141716A increases plasma corticosterone in rats and mice possibly through blockade of CB 1 receptors, an effect that is retained after subchronic dosing in mice. These data provide support for the notion that changes in plasma corticosterone concentrations may be used in the laboratory and the clinic to assess the effects of CB 1 receptor antagonism.

Mesocortical dopamine and HPA axis regulation: Role of laterality and early environment

The infralimbic (IL) cortex is importantly involved in regulating behavioral and physiological responses to stress, including those of the hypothalamic–pituitary–adrenal (HPA) axis. The mesocortical dopamine (DA) system is an important afferent modulator of this region, is highly stress sensitive and frequently shows functional hemispheric asymmetry. Postnatal handling stimulation facilitates development of cortical asymmetry and is also associated with optimal HPA axis regulation. The present study examines the poorly understood role of the mesocortical DA system in regulating HPA axis function in adult rats which were handled (H) or nonhandled (NH) postnatally. In the first experiment, unilateral intra-IL cortex injection of the DA (D1/D2) antagonist α-flupenthixol into either hemisphere significantly exaggerated the restraint stress-induced increases in plasma adrenocorticotrophic hormone and corticosterone in NH rats. In H rats, the same effect was lateralized to the right IL cortex. In a second experiment, post mortem neurochemical analysis of DAergic measures in the IL cortex was conducted in H and NH animals following either acute or repeated (5 times) restraint stress. DAergic measures in the right IL cortex were significantly correlated with reduced stress hormone activation in both H and NH rats, especially in repeatedly restrained rats. However, while H rats showed a significant rightward shift in DA metabolism with repeated stress experience, NH rats shifted DA metabolism to the left. It is suggested that, during stress, mesocortical DA release normally acts in an adaptive, negative feedback capacity preventing excessive HPA activation and, with repeated stress, the right IL cortex is particularly important in this capacity. As well, the selective enhancement of DA metabolism in the right IL cortex of H rats may underlie, in part, their typically superior ability to adapt to stress and constrain HPA activity.

Effect of single dose thalidomide on stress induced rise of plasma corticosterone in rats

Effect of single dose thalidomide on stress induced rise of plasma corticosterone in rats

Adrenal splanchnic innervation contributes to the diurnal rhythm of plasma corticosterone in rats by modulating adrenal sensitivity to ACTH

Activity of the hypothalamic-pituitary-adrenal axis is characterized by a diurnal rhythm with an AM nadir and PM peak. Splanchnic nerve transection disrupts the diurnal rhythm in plasma corticosterone; however, there is a controversy as to whether the nerve-mediated effect is 1) via inhibition in the AM vs. excitation in the PM, or 2) involves changes in adrenal sensitivity to ACTH. The present studies were designed to address these issues. Adult male rats were anesthetized and underwent bilateral transection of the thoracic splanchnic nerve or sham transection. One week after surgery, rats were killed in the AM or PM with collection of nonstress plasma for measurement of corticosterone and ACTH. Plasma corticosterone was increased in the PM relative to the AM; however, plasma corticosterone in the PM was attenuated by splanchnic nerve transection, without affecting plasma ACTH. This decrease in PM plasma corticosterone after nerve-transection was 1) associated with decreased adrenal responsivity to ACTH, 2) associated with decreased adrenal cAMP content, 3) prevented by adrenal demedullation, and 4) not affected by removal of adrenal capsaicin-sensitive afferent fibers. Repeated serial blood sampling from individual rats confirmed the excitatory effect of splanchnic innervation in the PM. These results support the hypothesis that the adrenal splanchnic innervation modulates the diurnal rhythm in plasma corticosterone by increasing adrenal responsivity to ACTH and augmenting steroidogenesis in the PM and suggest that alterations in adrenal corticosterone secretion obscured by pulsatile secretion are more clearly revealed with repeated serial blood sampling.

Maternal deprivation in neonatal rats alters the expression of circadian system under light–dark cycles and restricted daily feeding in adulthood

Effects of maternal deprivation (MD) with different conditions were examined on the circadian rhythms in plasma corticosterone and locomotor activity in adult rats under ad libitum and restricted daily feeding (RF), in which rats had free access to food for 2 h for 3 weeks. Three different types of MD were performed from postnatal day 1 (P1) to day 6 (P6); MD for 12 h/day (MD12), for 3 h/day in the morning (MD3am) and in the afternoon (MD3pm). Under ad libitum feeding, corticosterone levels at 08:00 h and 24:00 h were significantly increased in MD12 rats. A similar increase was detected in MD3am rats, but not in MD3pm rats. Under the RF, corticosterone levels at 08:00 h, 24:00 h, and 04:00 h were significantly increased in MD12 rats. Similar elevations were detected in MD3am rats, but not in MD3pm rats. Furthermore, prefeeding locomotor activities under the RF increased significantly in MD12 rats. A similar increase was observed in MD3am rats, but not in MD3pm rats. Keeping ambient temperature and humidity at 37 °C and 70–80% during MD attenuated the effects of MD on the corticosterone rhythmicities under RF as well as ad lib feeding. It is concluded that MD in the early postnatal period influences the expressions of circadian rhythms in plasma corticosterone and locomotor activity in adult rats. Not only the length but also the time of day of MD seems to be critical for these effects. Ambient temperature and/or humidity are suggested to be one of the factors by which MD exerts its effect.

Social isolation-induced changes in the hypothalamic–pituitary–adrenal axis in the rat

Social isolation of rats both reduces the cerebrocortical and plasma concentrations of 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) and 3α,5α-tetrahydrodeoxycorticosterone and potentiates the positive effects of acute stress and ethanol on the concentrations of these neuroactive steroids. We now show that social isolation decreased the plasma level of adrenocorticotropin (ACTH), moreover, intracerebroventricular administration of corticotropin releasing factor (CRF) induced a marked increase in the plasma corticosterone level in both isolated and group-housed rats, but this effect was significantly greater in the isolated rats (+121%) than in the group-housed rats (+86%). In addition, in isolated rats, a low dose of dexamethasone had no effect on the plasma corticosterone concentration, whereas, a high dose significantly reduced it; both doses of dexamethasone reduced plasma corticosterone in group-housed rats. Furthermore, the corticosterone level after injection of dexamethasone at the high dose was significantly greater in the isolated animals than in the group-housed rats. These results suggest that social isolation increased sensitivity of the pituitary to CRF and impaired negative feedback regulation of the hypothalamic–pituitary–adrenal (HPA) axis.

Hypoglycemic, antistress, anxiolytic, and nootropic activity of roots of Rubia cordifolia Linn

The alcoholic extract of dried roots of Rubia cordifolia dose dependently reduced blood sugar level in alloxan treated rats. The extract also reduced ulcer index, plasma corticosterone in cold restrain stressed rats in dose related manner. The mice treated with alcoholic extract of Rubia cordifolia spent more time in the open arm of the elevated plus maze indicating anxiolytic activity. The extract also antagonized the amnesic effect of scopolamine in mice as indicated by reduced transfer latency in the elevated plus maze. Thus the plant bears potential for use in diabetes, stress, anxiety, and dementia.

Insulin Alone Increases Hypothalamo-Pituitary-Adrenal Activity, and Diabetes Lowers Peak Stress Responses

Diabetes is associated with increased basal hypothalamo-pituitary-adrenal (HPA) activity and impaired stress responsiveness. Previously, we demonstrated that the HPA response to hypoglycemia is significantly impaired in diabetic rats. In this study our goals were to 1) differentiate between the effects of hyperinsulinemia and those of hypoglycemia per se, and 2) establish whether diabetes lowers peak stress responses. Normal and streptozotocin-diabetic rats were subjected to hyperinsulinemic-euglycemic glucose clamps to evaluate central and peripheral responses. These were compared with peak ACTH and corticosterone responses to restraint and hypoglycemia. Hyperinsulinemia increased CRH and vasopressin mRNA, and plasma ACTH and corticosterone in normal and diabetic rats. In normal animals, insulin-induced activation of ACTH and corticosterone was lower than the responses during either restraint or hypoglycemia. In contrast, ACTH and corticosterone activation in diabetic rats was similar with all three stressors. Pituitary-adrenal axis activation in diabetic animals was also much lower compared with that in normal controls. The response to hyperinsulinemia (euglycemia) was associated with increases in glucocorticoid receptor mRNA in the anterior pituitary and paraventricular nucleus. Hippocampal mineralocorticoid receptor mRNA expression was increased in normal, but not in diabetic, animals. We speculate that the ability to appropriately match the HPA response to the potency of a stressor is related to the ability to alter hippocampal mineralocorticoid receptor expression. In diabetes, this ability is impaired; hence, maximal HPA activation is greatly diminished. This is a novel observation that may have important implications in the treatment of impaired counterregulatory mechanisms in human diabetes.

P.1.120 Effects of Mice daily 3 h maternal separations on behaviour, plasma corticosterone and brain monoamines in adult female rats

P.1.120 Effects of Mice daily 3 h maternal separations on behaviour, plasma corticosterone and brain monoamines in adult female rats

Circadian rhythms on hypothalamic–pituitary–adrenal axis hormones and cytokines of collagen induced arthritis in rats

This study is designed to identify whether circadian rhythms of the hormones of the hypothalamic–pituitary–adrenal (HPA) axis are associated with corresponding circadian fluctuations in cytokines in a rat model of collagen-induced arthritis (CIA). CIA is induced in Wistar rats by an intradermal injection of bovine type II collagen emulsified with complete adjuvant at the left foot. On day 33, in both the CIA and the control rats, circulating adrenocorticotropin hormone (ACTH) and corticosterone, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6) and IL-1beta were evaluated at 6 h intervals from 00:00 to 24:00, and analyzed by statistics and cosinor-rhythmometry. The results showed that plasma corticosterone in CIA rats had a trough at 18:00 and reached a peak at 06:00 significantly. While peak values were presented in TNF-alpha at 24:00 and in IL-6 from 06:00 and 18:00 to 24:00. CIA rats exhibit abnormal circadian rhythms, with degrading amplitudes of corticosterone and IL-6, elevating amplitude of TNF-alpha, and marked phase shifts in corticosterone and IL-6. Our investigation suggests that the disorders of HPA axis in CIA rats may be related to the influence of inflammation mediators on hypothalamic centers. The circadian rhythms of hormones and cytokines in CIA rats may be reset due to the defective function of the HPA axis.

Corticotropin-releasing factor receptor type 1 and 2 mRNA expression in the rat anterior pituitary is modulated by intermittent hypoxia, cold and restraint

We had previously demonstrated that continual-hypoxia stimulated corticotropin-releasing factor (CRF)mRNA in hypothalamus, and release of CRF, as well as enhancing plasma adrenocorticotropic-hormone and corticosterone of rats. The present study demonstrates using in situ autoradiography that CRF receptor 1 (CRFR1) and CRF receptor 2 (CRFR2) mRNA in the rat anterior pituitary is changed by intermittent hypoxia, cold, restraint, alone and in combination. Rats were exposed to intermittent hypoxia for 4 h/day during various periods in a hypobaric chamber. Hypoxia equivalent to an altitude of around 2 km (16.0% O 2) or 5 km (10.8% O 2) caused a biphasic change in both CRFR1 and R2 mRNA, there being an initial significant decline on day 1 and then an enhancement by day 2. The increase of both receptor subtypes mRNA was relatively well maintained up to 15 days in rats exposed to 2 km intermittently. CRFR2 mRNA in rats exposed to 5 km, after peaking at day 2 therefore declined and was not different to controls at 15 days. Five kilometer hypoxia markedly reduced body weight gain. The increased CRFR1 mRNA was also induced by restraint alone, hypoxia+restraint and hypoxia+cold but not by cold alone. The CRFR2 mRNA was significantly increased by all the stresses except for hypoxia+restraint. These results show that the acute response to intermittent hypoxia is a decrease in the CRF receptor mRNA whereas longer exposure to the three environmental stressors hypoxia, cold and restraint is needed to provoke an increase. This may have important consequences for adaptation to high altitude. The significant differences between the expression of CRFR1 mRNA and CRFR2 mRNA in response to the different stimuli might suggest that the two receptors in the pituitary play different roles in behavior.

The effect of 3 or 6 weeks feeding of diets containing different fat source and content on deoxycorticosterone 11β-hydroxylase activity in adrenal gland and on plasma corticosterone and leptin concentration in rats

The effect of 3 or 6 weeks feeding of diets containing different fat source and content on deoxycorticosterone 11β-hydroxylase activity in adrenal gland and on plasma corticosterone and leptin concentration in rats

Extrahypothalamic corticotropin-releasing hormone mediates (−)-nicotine-induced elevation of plasma corticosterone in rats

(−)-Nicotine activates the hypothalamic–pituitary–adrenal axis via an activation of the brainstem catecholaminergic neurons in rats. The present study was undertaken to clarify the mechanisms involved in the (−)-nicotine-induced activation of brainstem catecholaminergic neurons in anesthetized rats. Physostigmine (a cholinesterase inhibitor) (0.31 and 0.77 μmol/animal, i.p.) dose-dependently elevated plasma corticosterone in the presence of scopolamine (a muscarinic receptor antagonist) (2.3 μmol/animal, i.p.). (−)-Nicotine (250 and 500 nmol/animal, i.c.v.) dose-dependently elevated plasma corticosterone with concomitant noradrenaline release in the hypothalamic paraventricular nucleus. The (−)-nicotine (500 nmol/animal, i.c.v.)-induced elevation of corticosterone was abolished by phentolamine (an α-adrenoceptor antagonist) (0.66 μmol/animal, i.c.v.), and attenuated by (±)-sotalol (a β-adrenoceptor antagonist) (0.97 μmol/animal, i.c.v.). The (−)-nicotine-induced increases of plasma corticosterone and hypothalamic noradrenaline release were abolished either by hexamethonium (a nicotinic acetylcholine receptor antagonist) (1.8 μmol/animal, i.c.v.), CP-154,526 (butyl-ethyl-[2,5-dimethyl-7-(2,4,6-trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl]amine) (a selective CRF-1 receptor antagonist) (1.3 μmol/animal, i.c.v.) or indomethacin (a cyclooxygenase inhibitor) (1.2 μmol/animal, i.c.v.). These results suggest that (−)-nicotine elevates plasma corticosterone by CRF-1 receptor- and prostaglandin-mediated noradrenaline release in the paraventricular nucleus in rats.

Effet synchroniseur du rythme circadien de la corticostérone sur la vitesse de synthèse du DNA dans le foie du jeune rat

Post-natal liver proliferation is synchronized by corticosterone circadian variation from the 21st day of life in rats. After tritiated thymidine injection, we compare the labelling index, the specific radioactivity of DNA, the DNA synthesis rate, the plasma corticosterone in un-rhythmed rats at day 15 and in rhythmed rats at day 25. No variation of these parameters is found during the 15th nycthemeron. During the 25th nycthemeron, the corticosterone circadian wave peaking at 18h is followed by the circadian variations of the 3 proliferation parameters peaking at 24 h.

Determination of corticosterone in rat and mouse plasma by gas chromatography-selected ion monitoring mass spectrometry

A simple, highly sensitive and specific method based on gas-chromatography-selected ion monitoring (SIM) mass spectrometry has been developed for the quantitation of corticosterone in rat and mouse plasma. After extraction of the plasma with ethyl acetate, the residue was trimethy-silylated with pentafluorobenzyl hydroxylamine-trimethylsilyl (PFBO-TMS). Detection of the derivatives was accomplished by a quadruple mass spectrometer in the selected ion monitoring mode ( m/ z of 316, 648, 663 and 678). The detection limit of the assay was 0.1 pg on column. The results show that in the plasma of non-stressed animals, only minor amounts of corticosterone were found; whereas in the plasma of stressed animals, it was dramatically increased. The method developed here can be used to examine corticosterone levels as a marker of stress in rats and mice and may also be used for estimation of the effect of stress-release medications.