Factors affecting the circadian rhythm in plasma cortisol concentrations in the horse

Irvine, C. H. G.; Alexander, Susan

doi:10.1016/0739-7240(94)90030-2

Cited by 199 publications

(140 citation statements)

References 24 publications

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“…These results are consistent with those of Larrson et al (1979) and Harewood and McGowan (2005), who observed no or hardly any circadian rhythm of cortisol concentration for such horses, but not with those of Moons et al (2002) and Irvine and Alexander (1994) who observed a circadian rhythm.…”

Section: Resultssupporting

confidence: 83%

Cortisol concentration in the saliva of horses subjected to different kinds of exercise

2011

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The aim of this study was to characterize the stress level in sport horses subjected to exercise by measuring the cortisol concentration in their saliva. The experiment was conducted on 5 groups of horses (49 animals): one control and four groups undergoing different types of exercises. The saliva samples were collected 3 × a day: late at night (between 20:00 and 23:00 h), early in the morning (between 5:00 and 8:00 h) and directly after the exercise. The concentration of cortisol was measured by the enzyme-immunoassay programme. The highest cortisol concentration was observed for the horses participating in 3-day events (8.93 nmol/dm 3 ), whereas in the control group it was only 0.28 nmol/dm 3 . When compared to the cortisol concentration of other horse groups, this suggests that the stress level as measured by the cortisol concentration in saliva increases with increasing exercise intensity and its duration. The obtained results do not confirm the existence of a day rhythm of the cortisol concentration in horses. Moreover, the results may help in choosing the appropriate system of training and in improving horse welfare during competitions.

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Section: Resultssupporting

confidence: 83%

Cortisol concentration in the saliva of horses subjected to different kinds of exercise

2011

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“…The prominent diurnal peak in circulating levels of adrenal steroids before the onset of the daily period of increased activity has been described in numerous species, including rats (Guillemin et al, 1959;McCarthy et al, 1960), monkeys (Perlow et al, 1981;Carnes et al, 1988), domestic animals (Lincoln et al, 1982;Klemcke et al, 1989;Lefcourt et al, 1993;Irvine and Alexander, 1994), and humans (Van Cauter, 1990;Linkowski et al, 1993). In diurnal species such as the human and the pig, plasma glucocorticoid levels are high in the early morning and then decline, reaching a nadir in the evening.…”

mentioning

confidence: 99%

A Diurnal Rhythm of Stimulatory Input to the Hypothalamo–Pituitary–Adrenal System as Revealed by Timed Intrahypothalamic Administration of the Vasopressin V₁Antagonist

et al. 1996

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The mammalian suprachiasmatic nuclei (SCN) contain an endogenous pacemaker that generates daily rhythms in behavior and secretion of hormones. We hypothesized that the SCN imposes its circadian rhythm on the rest of the brain via a rhythmic release of its transmitters in its target areas. Previously, we demonstrated a pronounced inhibitory effect of vasopressin (VP), released from SCN terminals in the dorsomedial hypothalamus, on the release of the adrenal hormone corticosterone. In the present study, microdialysis-mediated intracerebral administration of the VP V 1 -receptor antagonist was used to pursue the study of the mechanisms underlying the circadian control of basal corticosterone release. Using timed administrations of the VP antagonist divided equally over the day/night cycle, we were able to uncover the existence of an additional stimulatory input from the SCN to the hypothalamopituitary-adrenal (HPA) axis. Peak activity of this stimulatory SCN input takes place during the second half of the light period, after the daily peak of VP secretion, with a delay of ϳ4 -6 hr. In all likelihood, the inhibitory and stimulatory circadian input via separate mechanisms affects corticosterone release. Together, these two opposing circadian control mechanisms of the HPA axis enable a precise timing of the circadian peak in corticosterone release.

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“…We have found that even the comparatively mild stress of being housed in the novel environment of an indoor barn is enough to obliterate the circadian rhythm for several days in horses used to being kept on pasture [11]. Morning peak levels do not differ significantly between housed horses and horses in their normal environment, but evening trough levels are higher in the housed horses [11].…”

Section: What Changes Occur In the Adrenal Axis When A Horse Is Not Cmentioning

confidence: 77%

Stress in the Racing Horse: Coping vs Not Coping.

Alexander

Irvine

1998

JES

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Factors affecting the circadian rhythm in plasma cortisol concentrations in the horse

Cited by 199 publications

References 24 publications

Cortisol concentration in the saliva of horses subjected to different kinds of exercise

Cortisol concentration in the saliva of horses subjected to different kinds of exercise

A Diurnal Rhythm of Stimulatory Input to the Hypothalamo–Pituitary–Adrenal System as Revealed by Timed Intrahypothalamic Administration of the Vasopressin V₁Antagonist

Stress in the Racing Horse: Coping vs Not Coping.

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Factors affecting the circadian rhythm in plasma cortisol concentrations in the horse

Cited by 199 publications

References 24 publications

Cortisol concentration in the saliva of horses subjected to different kinds of exercise

Cortisol concentration in the saliva of horses subjected to different kinds of exercise

A Diurnal Rhythm of Stimulatory Input to the Hypothalamo–Pituitary–Adrenal System as Revealed by Timed Intrahypothalamic Administration of the Vasopressin V1Antagonist

Stress in the Racing Horse: Coping vs Not Coping.

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A Diurnal Rhythm of Stimulatory Input to the Hypothalamo–Pituitary–Adrenal System as Revealed by Timed Intrahypothalamic Administration of the Vasopressin V₁Antagonist