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Item Corticosterone responses to handling, and effects of corticosterone injections in the Japanese quail (Coturnix xoturni japonica) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Physiology at Massey University(Massey University, 2000) Boyd, Raewyn AnneThese studies examined the effects of corticosterone on the reproductive system, investigated the relationship between plasma and faecal corticosterone levels and defined corticosterones response to handling in the Japanese quail (Coturnix coturnix japonica). Six days of daily corticosterone injections decreased the area of the cloacal protuberance in both seven week old and six month old male quail. However, plasma testosterone levels 24 hours after an injection were only decreased in the six month old birds. There was a strong correlation between basal plasma and faecal corticosterone concentrations in the six month old birds. The effects of corticosterone during the 24 hours after an injection were then examined before and after six days of corticosterone injections in male quail. Corticosterone injections decreased plasma testosterone levels three-fold for 6-12 hours both after a single corticosterone injection and after six days of treatment. However, there were no changes in plasma luteinising hormone levels during the 24 hours after an injection. This result is consistent with corticosterone acting directly on the testes to decrease testosterone release. The rate of corticosterone removal from the blood after an injection increased after six days of corticosterone injections. Handling female Japanese quail for 15 minutes resulted in increased plasma corticosterone levels for less than 30 minutes. Mean corticosterone response curves were almost identical when the same birds were handled on three occasions. Although corticosterone response curves were similar during the early afternoon and during the night, basal corticosterone levels and the area under the corticosterone response curves were lower at night. Plasma corticosterone levels 0 and 15 minutes after the initiation of handling were more than twice as high in birds with large gonads than birds with small gonads. This study provides the first information in birds of a decrease in plasma testosterone levels within three hours of a corticosterone injection, independent of changes in plasma LH levels. It is also the first study in a domestic species to show larger corticosterone responses in female birds with large gonads than in birds with small gonads.Item Corticosterone, fear behaviour and plasma corticosterone responses to stressors in Japanese quail : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University, Palmerston North, New Zealand(Massey University, 2010) Wall, Julian PeterStress responses involve activation of the hypothalamo-pituitary-adrenal (HPA) axis and the secretion of glucocorticoid hormones, and can help animals cope with changes in their environments. Corticosterone is the primary glucocorticoid in birds and has metabolic actions, and can affect behaviour and reproduction. Stimuli that activate the HPA axis are called stressors, and stressors can be classified as either physical or emotional. When animals respond to emotional stressors they also experience fear, and the magnitude of a corticosterone response to an emotional stressor is thought to be related to the degree of fearfulness that is experienced by a bird. The great majority of studies have measured plasma corticosterone responses of birds to emotional rather than physical stressors, and corticosterone responses to emotional stressors are assumed to reflect the responsiveness of the HPA axis of birds to stressors in general. The aims of the research described in this thesis were to determine the effects of corticosterone on fear behaviour, reproductive function, and plasma corticosterone responses to stressors in Japanese quail (Coturnix coturnix japonica), both during and after treatment, and to examine if plasma corticosterone responses to similar emotional stressors, and to different types of emotional and physical stressors are related in individual quail. Plasma corticosterone concentrations were significantly higher in quail treated with corticosterone in their drinking water compared with controls during a 21 day treatment period, and concentrations remained elevated eight days after treatment ended. Corticosterone had little or no effect on the fearfulness of quail in tonic immobility, novel object or open field tests of fear behaviour. Body weight, food intake, egg production and egg weight were significantly lower in some corticosterone treatment groups than in controls during treatment and for up to 22 days after treatment ended. Corticosterone concentrations in quail were generally unaffected after 24 h of fasting, so the effects of elevated plasma corticosterone on corticosterone responses to a natural stressor in quail could not be determined. Corticosterone had marked effects on the physiology of quail for several weeks after treatment ended, suggesting that chronic elevations in plasma corticosterone resulting from climate change or human disturbance could have negative affects in birds even after exposure to a stressor ends. There were significant positive relationships between the magnitudes of plasma corticosterone responses to the emotional stressors of 15, 30 or 60 min handling followed by 45, 30 or 0 min confinement respectively in individual Japanese quail. Plasma corticosterone responses to 15 min handling followed by 45 min confinement are commonly measured in domesticated species of birds, and the findings of the present study suggest that magnitudes of responses to this standardised stressor may reflect the responsiveness of the HPA axis of birds to emotional stressors in general. Treatment with insulin and treatment with lipopolysaccharide (LPS) were shown to be physical stressors in quail, and doses and blood sampling times determined in insulin and LPS dose-response tests were used in a study of plasma corticosterone responses to emotional and physical stressors in quail. There were no relationships between corticosterone responses of individual birds subjected to emotional (handling) and physical (insulin and LPS) stressors, whereas there were significant correlations in responses of the birds to the two physical stressors. These results suggest that corticosterone responses of birds to standardised emotional stressors such as handling and confinement in domesticated species or capture and restraint in free-living species may not reflect the responsiveness of the HPA axis of birds to stressors in general. Given that quail displayed consistent individual differences in their plasma corticosterone responses to emotional stressors and to physical stressors, but magnitudes of corticosterone responses to both classes of stressor were unrelated in individual quail, these findings suggest that birds may possess at least two quite distinct stress responses to help them cope with changes in their environments.Item Corticosterone responses to stressors and the regulation of hypothalmic-pituitary-adrenal axis in Japanese quail : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Physiology at Massey University, Palmerston North, New Zealand(Massey University, 2003) Chua, Wei-HangCorticosterone is the major adrenal glucocorticoid in birds. It is secreted in response to stressors, with plasma concentrations typically rising to a peak within 10 to 15 minutes and then declining over 30 to 60 minutes once the stressor is removed. The increase in corticosterone is thought to help the animal to adjust to the stressor, although corticosterone may also inhibit the reproductive axis. The corticosterone response to a stressor varies between individuals, although the level of the hypothalamic-pituitary-adrenal axis at which this variation arises in birds has not been identified. The goals of this research were to determine in Japanese quail (Coturnix coturnix japonica): (1) the effects of corticosterone and of various stressors on sex steroid secretion; (2) corticosterone responses to 5, 10 or 15 min exposure to manual restraint and 15 min exposure to different stimuli; (3) quantifying individual variation in the corticosterone response; and (4) whether individual variation in the corticosterone response to stimuli used in goal 2 is regulated by differences in pituitary or adrenal sensitivity to corticotropin releasing factor (CRF) and adrenocorticotropic hormone (ACTH) respectively. A prolonged elevation in plasma corticosterone concentrations can inhibit reproduction. The effects of a short elevation in corticosterone are less understood, so the relationship between corticosterone and sex steroid secretion in quail was characterised by administering 1.2 mg corticosterone injections. Corticosterone treatment stimulated an increase in plasma corticosterone, while testosterone declined in both corticosterone-treated and control birds. Plasma LH was unaffected by challenge with corticosterone. Collectively, these data suggest that repeated handling associated with frequent blood sampling inhibited testosterone secretion directly at the testis. Corticosterone responses to a variety of novel stimuli were characterised. Manual restraint for 10 or 15 min caused a significant response whereas restraint for 5 min or less did not lead to an increase in corticosterone 15 minutes from the start of the stressor. Corticosterone responses to 15 min of mechanical restraint varied between birds whereas 15 min of manual restraint elicited a maximal plasma corticosterone response in all birds. Manual and mechanical restraint caused declines in plasma testosterone of a similar magnitude. There was more variation within than between birds in their corticosterone response to mechanical restraint. Despite this, the general pattern of the corticosterone response was repeatable for individuals. Quail with low or high plasma corticosterone responses to 15 minutes of mechanical restraint were injected intrajugularly with a dose of ACTH that stimulated a sub-maximal corticosterone response. The plasma corticosterone response to ACTH did not differ between birds with low or high corticosterone responses to mechanical restraint, indicating that variation in corticosterone responses to restraint did not arise at the level of the adrenal gland. A preliminary study showed that injections of ovine CRF stimulated corticosterone secretion. However, CRF did not consistently stimulate an increase in plasma corticosterone in these birds and hence it was not possible to determine if pituitary responsiveness to CRF differed between birds with low or high corticosterone responses to restraint. These results indicate that variation in the corticosterone response between individual Japanese quail arises above the level of the adrenal gland in the HPA-axis, and may occur at the pituitary gland or due to differences in activation of neural pathways in the brain.