Suppression of the secretion of luteinizing hormone due to isolation/restraint stress in gonadectomised rams and ewes is influenced by sex steroids

Tilbrook, AJ; Canny, Ben; Serapiglia,; Ambrose, TJ; Ij, Clarke

doi:10.1677/joe.0.1600469

Cited by 97 publications

(76 citation statements)

References 42 publications

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“…Consequently, the lack of a sex difference in the suppression of LH during stress suggests that glucocorticoids may not be a major mediator of the stress-induced suppression of LH. This is consistent with the conclusions of Tilbrook et al (1999) and studies conducted in other species (for review see Tilbrook et al 2000).…”

Section: Discussionsupporting

confidence: 92%

Influence of sex and gonadal status of sheep on cortisol secretion in response to ACTH and on cortisol and LH secretion in response to stress: importance of different stressors

Turner

Canny²,

Hobbs³

et al. 2002

Journal of Endocrinology

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There are sex differences in the response to stress and in the influence of stress on reproduction which may be due to gonadal steroids but the nature of these differences and the role of the gonads are not understood. We tested the hypotheses that sex and the presence/absence of gonads (gonadal status) will influence the cortisol response to injection of ACTH, insulin-induced hypoglycaemia and isolation/restraint stress, and that sex and gonadal status will influence the secretion of LH in response to isolation/ restraint stress. Four groups of sheep were used in each of three experiments: gonad-intact rams, gonadectomised rams, gonad-intact ewes in the mid-luteal phase of the oestrous cycle and gonadectomised ewes. In Experiment 1 (n=4/group), jugular blood samples were collected every 10 min for 6 h; after 3 h, two animals in each group were injected (i.v.) with ACTH and the remaining two animals were injected (i.v.) with saline. Treatments were reversed 5 days later so that every animal received both treatments. Experiment 2 (n=4/group) used a similar schedule except that insulin was injected (i.v.) instead of ACTH. In Experiment 3 (n=5/group), blood samples were collected every 10 min for 16 h on a control day and again 2 weeks later when, after 8 h of sampling, all sheep were isolated and restrained for 8 h. Plasma cortisol was significantly (P<0·05) elevated following injection of ACTH or insulin and during isolation/restraint stress. There were no significant differences between the sexes in the cortisol response to ACTH. Rams had a greater (P<0·05) cortisol response to insulin-induced hypoglycaemia than ewes while ewes had a greater (P<0·05) cortisol response to isolation/restraint stress than rams. There was no effect of gonadal status on these parameters. Plasma LH was suppressed (P<0·05) in gonadectomised animals during isolation/restraint stress but was not affected in gonadintact animals, and there were no differences between the sexes. Our results show that the sex that has the greater cortisol response to a stressor depends on the stressor imposed and that these sex differences are likely to be at the level of the hypothalamo-pituitary unit rather than at the adrenal gland. Since there was a sex difference in the cortisol response to isolation/restraint, the lack of a sex difference in the response of LH to this stress suggests that glucocorticoids are unlikely to be a major mediator of the stress-induced suppression of LH secretion.

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Section: Discussionsupporting

confidence: 92%

Influence of sex and gonadal status of sheep on cortisol secretion in response to ACTH and on cortisol and LH secretion in response to stress: importance of different stressors

Turner

Canny²,

Hobbs³

et al. 2002

Journal of Endocrinology

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“…Alternatively, the detrimental actions of cortisol on the secretion of LH may have been directly attenuated by oestradiol. This latter explanation does not support the finding that in rhesus macaques, 6 h of chair restraint inhibited the secretion of LH during the follicular phase of the menstrual cycle, when oestrogens are elevated, but not during the luteal phase (Norman et al 1994), or the finding, in ovariectomised sheep, that 4 h of isolation/restraint stress inhibited the secretion of LH in the presence and absence of oestradiol (Tilbrook et al 1999). Nevertheless, there might be species differences in the ability of oestrogens to influence the impact of stress on reproduction and/or the discrepancies between the results of these studies might be due to differences in the experimental paradigms.…”

Section: Discussionmentioning

confidence: 78%

“…Nevertheless, there might be species differences in the ability of oestrogens to influence the impact of stress on reproduction and/or the discrepancies between the results of these studies might be due to differences in the experimental paradigms. For instance, while stressors were imposed in the studies on rhesus macaques (Norman et al 1994) and sheep (Tilbrook et al 1999), cortisol was injected in the current experiment. The mechanism by which the sustained elevation of cortisol reduced the mean plasma concentrations of LH in the absence of oestradiol is not clear.…”

Section: Discussionmentioning

confidence: 99%

“…injection of cortisol, which resulted in a sustained elevation of plasma concentrations of cortisol, blocked the luteinizing hormone (LH) surge and ovulation in gilts (Barb et al 1982). Since the secretion of LH is central to reproduction, the measurement of plasma concentrations of LH has often been used to assess the effects of stress (Blake 1975, Doney et al 1976, Martin et al 1981, Stoebel & Moberg 1982, Rasmussen & Malven 1983, Dobson 1988, Norman et al 1994, Tilbrook et al 1999 and of administering hormones of the hypothalamopituitary-adrenal axis (Barb et al 1982, Hennessy & Williamson 1983, Paterson et al 1983, Fonda et al 1984, Pearce et al 1988, Frautschy et al 1989, Estienne et al 1991 on reproduction in females. For instance, prolonged treatment of ovariectomised pigs with cortisol inhibited the secretion of LH (Estienne et al 1991).…”

Section: Introductionmentioning

confidence: 99%

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Inhibition of the secretion of LH in ovariectomised pigs by sustained but not repeated acute elevation of cortisol in the absence but not the presence of oestradiol

Turner

Hemsworth

Canny³

et al. 1999

Journal of Endocrinology

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Prolonged stress is known to impair reproduction. It has been proposed that reproduction will also be impaired when a severe acute stress occurs during a period of elevated plasma concentrations of oestradiol, such as during the follicular phase of the oestrous cycle. In this experiment, we hypothesised that repeated acute and sustained elevation of cortisol would suppress the secretion of LH in ovariectomised pigs and that these effects would be enhanced in the presence of oestradiol negative feedback. Cortisol (or vehicle) was administered 12 hourly to ovariectomised pigs (n=6/treatment) for 8 days in the absence of oestradiol treatment and for a further 8 days during treatment with oestradiol. Vehicle was administered to 'control' pigs, 10 or 20 mg cortisol was administered i.v. to pigs to produce 'repeated acute' elevation of cortisol and 250 mg cortisol was administered i.m. to pigs to give a 'sustained' elevation of cortisol. Both before and during treatment with oestradiol, plasma concentrations of LH were monitored on the day before treatment, on the 4th and 8th days of treatment and following an i.v. injection of GnRH at the end of the 8th day of treatment. The repeated acute elevation of cortisol did not impair any parameters of LH secretion (i.e. mean plasma concentrations of LH, pulse amplitude or frequency, pre-LH pulse nadir or the LH response to GnRH) in the absence or in the presence of oestradiol. In contrast, when the elevation of cortisol was sustained, the mean plasma concentrations of LH and the pre-LH pulse nadir were significantly (P<0·05) lower on the 8th day of treatment than on the day before treatment and on the 4th day of treatment. Nevertheless, no other parameters of LH secretion were affected and these effects only occurred in the absence (not in the presence) of oestradiol. In conclusion, cortisol needed to be elevated for more than 4 days to impair the secretion of LH, and oestradiol did not enhance the impact of cortisol on LH secretion in ovariectomised pigs.

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“…This absence of a diurnal decrease in circulating cortisol levels suggests at least partial activation of the HPA axis in female marmosets restrained for hypothalamic push-pull perfusion. Adaptation of the monkeys to the restraint (Wade & Ortiz 1997), the amount of movement permitted while in the restraint (Wade & Ortiz 1997), and the close visual proximity of cage mates (Tilbrook et al 1999) may all minimize the elevation of circulating cortisol levels in restrained animals. These restraint-associated elevations in circulating cortisol levels were of a substantially smaller magnitude than those observed in female marmosets following wounding incurred during establishment of intra-sexual social dominance hierarchies over 3 days of new group formation (Saltzman et al 1994).…”

Section: Discussionmentioning

confidence: 99%

Novel restraint system for neuroendocrine studies of socially living common marmoset monkeys

et al. 2004

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We describe a novel soft jacket and sling-harness restraint that permits species-typical postures for small-bodied primates, such as the common marmoset (Callithrix jacchus), during long-term (>6 h), continuous restraint. The restraint system is straightforward to use and manipulate, it is easily repaired, and the materials used are readily available. The soft jacket allows for increased versatility and longevity, and the sling-harness provides for greater movement and much longer duration of continuous restraint (up to 3 days) compared to a previously described, more conventional chair restraint for small-bodied primates. The new restraint system prevents the normal diurnal decrease in plasma cortisol levels across the daylight hours; however, it does not disrupt ovulatory cycles. Unlike the previously available techniques, therefore, this new restraint system is applicable to many neurobiological and neuroendocrine studies involving small-bodied, non-human primates and is especially suited to investigations requiring the maintenance of relationships within social groups.

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Suppression of the secretion of luteinizing hormone due to isolation/restraint stress in gonadectomised rams and ewes is influenced by sex steroids

Cited by 97 publications

References 42 publications

Influence of sex and gonadal status of sheep on cortisol secretion in response to ACTH and on cortisol and LH secretion in response to stress: importance of different stressors

Influence of sex and gonadal status of sheep on cortisol secretion in response to ACTH and on cortisol and LH secretion in response to stress: importance of different stressors

Inhibition of the secretion of LH in ovariectomised pigs by sustained but not repeated acute elevation of cortisol in the absence but not the presence of oestradiol

Novel restraint system for neuroendocrine studies of socially living common marmoset monkeys

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