Noradrenaline, but Not Neuropeptide Y, Is Elevated in Cerebrospinal Fluid from the Third Cerebral Ventricle following Audiovisual Stress in Gonadectomised Rams and Ewes

Abstract

There are sex differences in the activation of the hypothalamo-pituitary-adrenal axis in response to stress, but the source of these differences is unknown. The hypothalamo-pituitary-adrenal axis is regulated by corticotropin-releasing hormone and arginine-vasopressin neurones located in the paraventricular nucleus and these, in turn, are regulated by neural systems that include afferent noradrenergic and neuropeptide Y (NPY)-producing neural pathways. We tested the hypothesis that concentrations of noradrenaline and NPY will be elevated in cerebrospinal fluid (CSF) sampled from the third cerebral ventricle in response to stress, and these responses will differ in males and females. We collected concurrent samples of CSF (1 ml) from the third ventricle and blood (5 ml) from the jugular vein from gonadectomised rams (n = 7) and ewes (n = 5) at 10-min intervals for 3 h. This procedure was conducted on a day when no stress was imposed and on a day when audiovisual stress was imposed for 5 min after 1 h of sampling. Following the audiovisual stress, plasma concentrations of cortisol and CSF concentrations of noradrenaline were elevated (p < 0.05), but CSF concentrations of NPY did not change. Adrenaline was not detected in samples of CSF. The rise in plasma cortisol following the stress was greater (p < 0.05) in ewes than in rams, but there were no sex differences in the rise in noradrenaline. Basal concentrations of NPY in the CSF were higher (p < 0.05) in rams than in ewes. We conclude that the sex differences in the stress-induced activity of the hypothalamo-pituitary-adrenal axis in sheep are not likely to be due to differences in the level of noradrenergic and/or NPY input to the hypothalamus.

A sex difference in the cortisol response to tail docking and ACTH develops between 1 and 8 weeks of age in lambs

“…At 8 weeks of age, the stressor imposed, tail docking, clearly invoked a greater cortisol response in females than in males. In this regard, it is similar to isolation-restraint stress (Turner et al 2002a) and audiovisual stress (Turner et al 2002b) in adult sheep but differs to insulin-induced hypoglycaemia (Turner et al 2002a) in which it was the males that had a greater response than Figure 2 Mean ( S.E.M.) plasma concentrations of cortisol (ng/ml; left-hand axes) in male lambs that were sham handled d, tail docked or tail docked and castrated and mean ( S.E.M.)…”

“…There are differences between the sexes in adult sheep in the cortisol response to stress and it appears that the type of stressor imposed influences the nature of these differences. For instance, females have been found to have a greater cortisol response than males to isolation-restraint stress (Turner et al 2002a) and to an audiovisual stress that involved exposure to a barking dog (Turner et al 2002b). In contrast, males have a greater cortisol response than females to insulin-induced hypoglycaemia (Turner et al 2002a).…”

“…Thus, we tested the hypothesis that there are sex differences in the cortisol response to tail docking and ACTH in lambs of 1 and 8 weeks of age. Furthermore, since our studies with different stressors in adult sheep also suggest that the magnitude of the cortisol response is proportional to the severity of the stressor encountered (Turner et al 2002a(Turner et al , 2002b, we also established cortisol responses in males when tail docking was imposed alone or in combination with castration at 1 and 8 weeks of age. Castration is another severe stressor that male lambs of these ages may encounter as a part of routine husbandry.…”

Impact of psychosocial stress on gonadotrophins and sexual behaviour in females: role for cortisol?

“…Norepinephrine has also been shown to increase transiently during sexual receptivity and following periods of sexual interactions with a male (Fabre-Nys et al 1997). Interestingly, stress increases central norepinephrine concentrations in sheep (Turner et al 2002b). Noradrenaline, but not neuropeptide Y, is elevated in cerebrospinal fluid from the third cerebral ventricle following audio-visual stress in gonadectomized rams and ewes (Turner et al 2002b); however, the impact of this on sexual behaviour has not been investigated.…”

“…Interestingly, stress increases central norepinephrine concentrations in sheep (Turner et al 2002b). Noradrenaline, but not neuropeptide Y, is elevated in cerebrospinal fluid from the third cerebral ventricle following audio-visual stress in gonadectomized rams and ewes (Turner et al 2002b); however, the impact of this on sexual behaviour has not been investigated. There is evidence that serotonin and γ-aminobutyric acid inhibit oestrous behaviour in rodents and sheep (Ågmo et al 1989, Mendelson 1992, Turner et al 2002b, Fabre-Nys & Gelez 2007; however, their possible roles as mediators of the effects of stress on sexual behaviour in other species have not been investigated.…”