Circadian rhythmicity of ACTH and corticosterone in the rat

Allen-Rowlands, C. F.; Allen, John P.; Greer, Monte A.; Wilson, Marlene

doi:10.1007/bf03349373

Cited by 41 publications

(33 citation statements)

References 23 publications

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“…Because changes in plasma corticosterone in response to acute stress are known to occur relatively slowly (over a period of minutes) (9,28,29) compared with more immediate I-ACTH changes, these results indicate that differences observed between the chronically cannulated and the decapitated rats reflect the stress associated with sampling. A similar effect of sampling stress may also explain why Allen-Rowlands et al (5) were able to show clear diurnal variation in plasma corticosterone, but not in plasma I-ACTH, in decapitated male and female rats.…”

Section: Discussionmentioning

confidence: 78%

Circadian Variation in Basal Plasma Corticosterone and Adrenocorticotropin in the Rat: Sexual Dimorphism and Changes across the Estrous Cycle*

1997

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Sexual dimorphism in the rat hypothalamic-pituitary-adrenal axis was investigated by determination of plasma corticosterone and immunoreactive (I-) ACTH in males and in females at each stage of the estrous cycle. A serial blood-sampling technique enabled assessment of covariation of the two hormones across the full circadian range of their concentrations within individual animals. Distinct diurnal rhythms in plasma corticosterone were evident in all rats, and the degree and timing of this rhythmicity, determined by cosinor analyses, did not vary with gender or cycle stage. There were, however, marked differences in absolute levels of corticosterone across the estrous cycle, with the average daily concentration (mesor) increasing progressively from a minimum at estrus (129 Ϯ 11 ng/ml) to a maximum 3 days later at proestrus (246 Ϯ 14 ng/ml). The mesor corticosterone value in male rats (102 Ϯ 21 ng/ml) was not different from that in estrous females, but was lower than that in females at all other stages of the cycle. In contrast, no gender-or cycle-related differences were detected in absolute levels of I-ACTH, although distinct diurnal rhythms, synchronous with those for corticosterone, were evident in all groups. Accordingly, a strong and positive within-rat relationship between plasma corticosterone and I-ACTH was observed in all groups, but there was a clear shift in the nature of this relationship across the estrous cycle, such that the slope (i.e. concentration of plasma corticosterone per unit concentration of I-ACTH) was minimal in males and estrous females and maximal in proestrous females. In conclusion, this study shows that the extent of sexual dimorphism in resting plasma corticosterone levels is dependent on estrous cycle stage, being absent at estrus and maximal at proestrus. Moreover, this variation in plasma corticosterone was not accompanied by corresponding changes in plasma I-ACTH, suggestive of cycle-related changes in responsiveness of the adrenal cortex to trophic stimulation. (Endocrinology 138: 3842-3848, 1997) S EXUAL DIMORPHISM is a feature of the rat hypothalamic-pituitary-adrenal (HPA) axis, with higher plasma corticosterone levels consistently reported for female compared with male rats (1-8). This sex difference appears most pronounced at the peak of the circadian rhythm (1, 3, 4, 7) and is thought to reflect activation of the HPA axis by ovarian estrogen (1, 6, 9, 10). Accordingly, several studies have also identified changes in plasma corticosterone associated with estrous cycle stage, with peak corticosterone levels highest at proestrus (11-13), the time of maximal estrogen secretion (14). Interestingly, previous reports on gender differences in the rat HPA axis (2-8) have considered females as a single group with apparently no account taken of stage, length, or regularity of estrous cycles. Thus, it is possible that sexual dimorphism in plasma corticosterone occurs only when females are at those stages of the cycle when estrogen levels are high.Several previous studies ind...

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Section: Discussionmentioning

confidence: 78%

Circadian Variation in Basal Plasma Corticosterone and Adrenocorticotropin in the Rat: Sexual Dimorphism and Changes across the Estrous Cycle*

1997

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“…2b). The CORT response was significantly higher in the OVX group compared to the steroid replacement groups at every time point poststress except at 60 min (overall treatment: F = 5.12 [2,15]; p = 0.02; treatment and time interaction: F = 4.41; p = 0.0007). Again, the initial rate rise of CORT was significantly (p < 0.05) higher in the OVX group (31.1 ng/ml x min) compared to the group with E2 pellets (21.5 ng/ml x min) or the group with both E2 and P pellets (13.7 ng/ml x min).…”

Section: Fast Feedback Inhibition By Rising Levels O F Co Rt On a Submentioning

confidence: 87%

“…ACTH levels were ele vated in the ovariectomized group even at 20 min after the onset of the initial stress, while by this time ACTH levels were no longer different from basals in the other two groups. There was an overall treatment effect (F = 16.87 [2,15];p = 0.0001), a highly significant time effect, and a time and treatment interaction (F = 5.00; p = 0.003). Post hoc comparisons revealed that the OVX+E: and the OVX+Ei+P groups did not differ from each oth er, but were different from OVX at every time point poststress except at 60 min.…”

Section: Fast Feedback Inhibition By Rising Levels O F Co Rt On a Submentioning

confidence: 91%

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Fast Glucocorticoid Feedback Inhibition of ACTH Secretion in the Ovariectomized Rat: Effect of Chronic Estrogen and Progesterone

et al. 1994

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The purpose of this study was to determine whether estrogen and progesterone influence fast glucocorticoid negative feedback regulation of the ACTH and corticosterone (CORT) responses to stress. Mature rats were ovariectomized and 6 weeks later implanted with 17β-estradiol (E₂,0.5 mg), E₂ and progesterone (P, 100 mg; E₂+P group) or placebo pellets (OVX). Seven days later rats were subjected to a single or repeated intermittent footshock stress (0.2 mA, 15 s duration, 0.5 s on). The repeated stress was of the same intensity and duration, and was applied either during the time domain of the rate-sensitive fast glucocorticoid feedback when plasma CORT levels are rising (5 min after the onset of the first stress), or at the time of peak CORT response (15 min) to the initial stress. Plasma ACTH and CORT were measured from serial samples. Estrogen replacement alone or in combination with progesterone lowered the immediate (t = 5) ACTH and CORT response to a single stress in ovariectomized animals. The second stress applied 5 min after the initial stress produced net ACTH responses similar to those obtained after a single stress in the OVX and E₂+P-replaced hormone groups, while total ACTH responses were lower in the E₂-treated group. In ovariectomized animals, a facilitation of ACTH response by a prior stress is apparent in response to a footshock 15 min later, when the integrated ACTH secretion is significantly greater than the response measured after a single shock, or after a repeated shock 5 min apart. Anterior pituitary proopiomelanocortin (POMC) mRNA levels were lower in groups with E₂ or E₂+P replacement compared to OVX animals. In contrast, hypothalamic corticotropin-releasing factor (CRF) mRNA levels did not increase significantly. However, hypothalamic glucocorticoid receptor (GR) mRNA levels increased after 17β-estradiol treatment, and this increase was reversed by progesterone. These results suggest that prior stress leads to both a fast-feedback inhibition and a facilitation of the subsequent stress response. In the absence of gonadal hormones this facilitation is balanced by fast-feedback inhibition during the glucocorticoid fast-feedback time domain, and is unmasked outside of this time domain. Estrogen suppresses POMC mRNA synthesis leading to a decrease in the availability of releasable ACTH, thereby reducing the facilitation. Progesterone may counter this effect of estrogen by decreasing the efficacy of the fast rate-sensitive glucocorticoid negative feedback.

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“…see ref . 18] and that it is involved not only in the control of the ACTH/corticosterone response to stress or to insulin administration [19,20], but also in regulation of the ACTH/corticosterone rise during the morning hours [21,22], Corticosteroids and ACTH have a diurnal rhythm with a nadir in the light period and peak secretion during the dark period [23]. Studies of Bellomo et al [24] have shown lower 24-hour integrated concentra tions of ACTH/cortisol in parkinsonian patients as com pared with normal controls and have suggested that a hypothalamic disturbance is responsible for this disorder.…”

Section: Discussionmentioning

confidence: 99%

ACTH/Cortisol Involvement in the Serotonergic Disorder Affecting the Parkinsonian Brain

Volpi

Caffarra²,

Boni³

et al. 1997

Neuropsychobiology

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In order to establish whether the serotonergic disorder affecting the parkinsonian brain also modifies hypothalamic-pituitary function in Parkinson’s disease, 10 patients (aged 57–66 years) and 10 normal controls (aged 55–69 years) were tested with the serotonergic agonist d,l-fenfluramine (60 mg p.o.), with CRH (100 µg i.v.) and with placebos. Plasma ACTH/cortisol levels during tests were evaluated and compared. Both groups showed similar levels of ACTH and cortisol in basal conditions and after placebo administration. A slight physiological decline in both ACTH and cortisol levels during the placebo test was observed in normal controls and parkinsonian patients. CRH induced similar ACTH/cortisol increments in all subjects. In contrast, d,l-fenfluramine significantly increased plasma ACTH/cortisol concentrations in the normal controls, but not in the parkinsonian patients. These data show a defective serotonergic control of the pituitary-adrenal axis in Parkinson’s disease.

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Circadian rhythmicity of ACTH and corticosterone in the rat

Cited by 41 publications

References 23 publications

Circadian Variation in Basal Plasma Corticosterone and Adrenocorticotropin in the Rat: Sexual Dimorphism and Changes across the Estrous Cycle*

Circadian Variation in Basal Plasma Corticosterone and Adrenocorticotropin in the Rat: Sexual Dimorphism and Changes across the Estrous Cycle*

Fast Glucocorticoid Feedback Inhibition of ACTH Secretion in the Ovariectomized Rat: Effect of Chronic Estrogen and Progesterone

ACTH/Cortisol Involvement in the Serotonergic Disorder Affecting the Parkinsonian Brain

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