The role of endogenous opioids in neurohypophysial and hypothalamo-pituitary-adrenal axis hormone secretory responses to stress in pregnant rats

Douglas, Alison J.; Johnstone, Heather A.; Wigger, A.; Landgraf, Rainer; Russell, John A.; Neumann, Inga D.

doi:10.1677/joe.0.1580285

Cited by 97 publications

(86 citation statements)

References 54 publications

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“…administration of naloxone general EOP antagonist, as it is documented in rats (Leng et al, 1988;Douglas et al, 1998) or sows (Lawrence et al, 1992). These data suggest that endogenous opioids are involved in the central inhibition of oxytocin release in response to mechanical stimuli.…”

Section: Opioid Controlsupporting

confidence: 56%

Factors affecting milk ejection and removal during milking and suckling of dairy cows

Tančin¹,

Bruckmaier²

2001

Vet. Med.

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The release of oxytocin and milk ejection occurrence in response to teat stimulation are crucial for fast and complete milk removal during milking or suckling. The milk ejection reflex can be disturbed at central or peripheral level under different experimental and practical conditions. The central disturbance results in the lack or insufficient ejection of the alveolar milk into the cistern due to inhibited oxytocin release from pituitary into the blood circulation. The important role in the pathophysiological regulation of the inhibited release of oxytocin is played by an opioid system. Endogenous opioids have suppressive effects on oxytocin release under the normal conditions of milk removal. However under the conditions of disturbed milk ejection their role in dairy cows was not confirmed. Other possible mechanisms involved in the central inhibition of oxytocin release are discussed. In dairy cows as compared with rats the mechanisms involved in the regulation of oxytocin release at the central level remain unclear. The central inhibition of oxytocin release has often been observed in dairy practice during milking of primiparous cows after parturition, suckling by alien calf, calf removal before milking, milking of cows in the presence of own calf, relocation and milking in an unknown milking place. If sufficient released oxytocin cannot induce the transfer of milk from alveoli to cistern, peripheral mechanisms are involved. Peripheral mechanisms are related to the increased levels of catecholamines and/or activation sympathetic nervous system at the udder level. In conclusion, the release of oxytocin and milk ejection efficiency can be very easily suppressed by many factors. The effect of milking conditions on regulation of milk ejection has to be considered. Thus the physiological requirements of dairy cows have to be respected.

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Section: Opioid Controlsupporting

confidence: 56%

Factors affecting milk ejection and removal during milking and suckling of dairy cows

Tančin¹,

Bruckmaier²

2001

Vet. Med.

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“…Adaptations of HPA axis activity in the peripartum period occur at all brain levels, including reduction in the activity of hypothalamic CRF neurons (57), reduced excitatory inputs to these neurons (58,59), and reduced CRF binding at the adenohypophysis (3) to name a few. These adaptations are reversible upon weaning (7).…”

Section: Discussionmentioning

confidence: 99%

Effects of Suckling on Hypothalamic-Pituitary-Adrenal Axis Responses to Psychosocial Stress in Postpartum Lactating Women

Heinrichs

Meinlschmidt

Neumann

et al. 2001

The Journal of Clinical Endocrinology &Amp; Metabolism

290

115

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In several studies lactation has been shown to be associated with a hypothalamic-pituitary-adrenal axis hyporesponsiveness to physical and psychological stressors. As it is not known whether the marked blunting of endocrine stress reactivity in women can be ascribed to suckling as a short-term effect or to lactation in general, the acute effects of suckling on the hypothalamic-pituitary-adrenal axis and the sympathetic-adrenal-medullary system responses to mental stress were investigated in lactating women.Forty-three lactating women were randomly assigned either to breast-feed or to hold their infants for a 15-min period with the onset 30 min before they were exposed to a brief psychosocial stressor (Trier Social Stress Test). Both breastfeeding and holding the infant yielded significant decreases in ACTH, total plasma cortisol, and salivary free cortisol (all P < 0.01). There were no significant differences in baseline hormone levels between the groups 1 min before the stress test. In response to stress exposure, ACTH, total plasma cortisol, salivary free cortisol, norepinephrine, and epinephrine were significantly increased in all lactating women (all P < 0.001). However, total cortisol and free cortisol responses to stress were attenuated in breast-feeding women (P ‫؍‬ 0.001 and P ‫؍‬ 0.067, respectively), who also showed significantly decreasing PRL levels during the stress test (P ‫؍‬ 0.005). In addition, there was no change in plasma oxytocin or vasopressin in response to the stressor. Breast-feeding as well as holding led to decreased anxiety (P < 0.05), whereas, in contrast, stress exposure worsened mood, calmness, and anxiety in the total group (all P < 0.001).From these data we conclude that lactation in women, in contrast to that in rats, does not result in a general restraint of the hypothalamic-pituitary-adrenal axis response to a psychosocial stressor. Rather, suckling is suggested to exert a short-term suppression of the cortisol response to mental stress. (J Clin Endocrinol Metab 86: 4798 -4804, 2001) E VIDENCE FROM ANIMAL and human studies has suggested that suckling is associated with significant alterations in the reactivity of the hypothalamic-pituitaryadrenal (HPA) axis during the postpartum period (1, 2). Observations in the lactating rat have shown an endocrine hyporesponsiveness to physical and psychological stressors, including attenuated secretion of ACTH (3-7), corticosterone (3-5, 8 -11), catecholamines (12), oxytocin (9, 13-15), and PRL (12, 16).In humans, the effect of lactation on stress-responsive neurohormonal systems has been explored, to date, only for treadmill exercise. Altemus and associates (17) found significantly attenuated plasma ACTH, cortisol, and glucose responses to physical stress in lactating compared with nonlactating women. However, the effects of suckling on endocrine as well as behavioral responses to a psychosocial stress paradigm in humans have not yet been investigated. More important, it is not known whether the marked blunting of endocrine stress responsi...

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“…In contrast, a stimulatory effect of endogenous opioids on the HPA axis response to physical stress has been reported in virgin rats (25).…”

Section: Discussionmentioning

confidence: 86%

Morphine-induced stimulation of pituitary-adrenocortical activity is mediated by activation of nitric oxide in the early stages of postnatal life in the rat

Lésage

Bernet²,

Montel³

et al. 2001

European Journal of Endocrinology

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Objective: The first aim of the present study was to determine if morphine, a prototypic m-opioid agonist drug, affects pituitary±adrenocortical activity in developing rat pups (first and second weeks of postnatal life). The second aim of this study was to explore, in vivo, if nitric oxide (NO) could be involved in the neurohormonal response to morphine in the early stages of postnatal life. Methods: Plasma ACTH and corticosterone concentrations were determined by RIA in rat pups n 5±14 rats/experimental group) after they had been killed by decapitation. In a first experiment, 1-day and 1-and 2-week-old rats were treated s.c. with morphine (20 mg/kg) or with vehicle (0.9% NaCl) and killed 5±90 min later. In a second experiment, 2-week-old pups were pretreated s.c. with naltrexone (NAL; 0.4 mg/kg or 10 mg/kg), and injected 1 h later with either morphine (20 mg/kg) or vehicle, and killed 30 min later. Some pups injected with only NAL were killed 60 or 90 min later. On the other hand, pups injected with NAL (10 mg/kg) or NAL and morphine were killed 30 min later. In a third experiment, 2-week-old pups were pretreated s.c. with N-v-nitro L arginine methylester (L-NAME; 30 mg/kg or 100 mg/kg), and injected 1 h later with either morphine (20 mg/kg) or vehicle, and killed 30 min later. Moreover, some pups injected with L-NAME (100 mg/kg) or L-NAME with morphine were killed 30 min later. In a final experiment, pups were injected s.c. with either S-nitroso-N-acetylpenicillamine (SNAP; 5 mg/kg) or vehicle, and killed 60 or 90 min later. Results: Morphine administered to rat pups elicited marked rises in both ACTH and corticosterone secretion. Moreover, these responses increased with advancing postnatal age. In 2-week-old rat pups, NAL, a competitive antagonist at m-opioid receptors, administered alone increased both plasma ACTH and corticosterone concentrations 30 min later. L-NAME, a specific NO synthase inhibitor, did not affect plasma ACTH and corticosterone concentrations 30 min later when administered alone. NAL, when concomitantly administered with morphine, was unable to block morphine responses. In contrast, morphine responses were blocked by pretreatment (60 min before) with NAL or with L-NAME. Acute injection of SNAP increased both ACTH and corticosterone release. Conclusion: Our results suggest that opioids have controversial effects on pituitary±adrenocortical activity in the early postnatal period in the rat, and that endogenous NO is one of the major factors in the response of the pituitary±adrenocortical axis to morphine.

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The role of endogenous opioids in neurohypophysial and hypothalamo-pituitary-adrenal axis hormone secretory responses to stress in pregnant rats

Cited by 97 publications

References 54 publications

Factors affecting milk ejection and removal during milking and suckling of dairy cows

Factors affecting milk ejection and removal during milking and suckling of dairy cows

Effects of Suckling on Hypothalamic-Pituitary-Adrenal Axis Responses to Psychosocial Stress in Postpartum Lactating Women

Morphine-induced stimulation of pituitary-adrenocortical activity is mediated by activation of nitric oxide in the early stages of postnatal life in the rat

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