Stress-Induced Changes in Plasma, Pituitary and Hypothalamic Immunoreactive β-Endorphin: Effects of Diurnal Variation, Adrenalectomy, Corticosteroids, and Opiate Agonists and Antagonists

Lim, Alan T.; Funder, John W.

doi:10.1159/000123460

Cited by 68 publications

(27 citation statements)

References 30 publications

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“…However, the levels of P-endorphin IR and y-endorphin IR were not affected by adrenalectomy. In another study also no change was observed in hypothalamic p-endorphin IR content after 6 days of adrenalectomy [26].…”

Section: Discussionmentioning

confidence: 86%

“…This finding suggests that glucocorticoids act on enzymes capable of y-endorphin for mation, in addition to the well-documented action on POMC gene transcription. POMC messenger RNA pool, biosynthesis of POMC peptides, and the release of POMC peptides from the anterior pituitary gland [18,19,26,33,34].…”

Section: Discussionmentioning

confidence: 99%

“…It is well known that synthesis and release of POMCrelated peptides in the anterior pituitary gland is under con trol of glucocorticoids [19,26,31,33,34], The present study was designed to investigate whether glucocorticoids also control y-endorphin levels and formation in the anterior pi tuitary gland. Therefore, we have investigated the effect of adrenalectomy and corticosterone substitution on the levels of y-endorphin, [3-endorphin, and Leu-Phe cleaving activity in the anterior pituitary gland.…”

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confidence: 99%

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Leu-Phe Cleaving Endopeptidase Activity, γ-Endorphin, and β-Endorphin in the Rat Pituitary Gland and Brain

Lebouille¹,

Burbach²,

Kloet³

et al. 1988

Neuroendocrinology

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The influence of adrenalectomy and corticosterone substitution was investigated on Leu-Phe cleaving endopeptidase activity and on the levels of γ-endorphin and β-endorphin in the pituitary gland and the brain. The enzyme activity was quantitated by a specific radiometric assay based on the cleavage of the Leu¹⁷-Phe¹⁸ bond in a NH₂ and COOH-terminally protected synthetic substrate wich was analogous to β-endorphin-(15–19). This activity may mimick the formation of γ-endorphin. β-Endorphin and γ-endorphin were measured by specific radioimmunoassays. After 14 days of adrenalectomy enzyme activity had increased in anterior (15%) and neurointermediate lobes of the pituitary gland (30%), hypothalamus (25%), and liver (15%). This increase was prevented when the adrenalectomized animals were subjected to chronic corticosterone substitution by subcutaneous implantation of a pellet of 100 mg. Extirpation of only the adrenal medulla did not affect the Leu-Phe cleaving activity. Enzyme activity in the septum, hippocampus, and cerebellum had not changed after adrenalectomy. Determination of immunoreactive levels of γ- and β-endorphins showed that in the anterior pituitary gland γ- and β-endorphins had increased by 275 and 300%, respectively, 14 days after adrenalectomy. No significant changes were observed in endorphin levels of the intermediate lobe of the pituitary gland, hypothalamus, hippocampus, and septum. The results indicate that Leu-Phe cleaving endopeptidase activity is sensitive to glucocorticoids in tissues containing proopiomelanocortin-producing cells, i.e., anterior and neurointermediate pituitary gland and the hypothalamus. In the anterior pituitary gland it is correlated with the levels of γ- and β-endorphins.

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Section: Discussionmentioning

confidence: 86%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Leu-Phe Cleaving Endopeptidase Activity, γ-Endorphin, and β-Endorphin in the Rat Pituitary Gland and Brain

Lebouille¹,

Burbach²,

Kloet³

et al. 1988

Neuroendocrinology

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“…On the basis of these considerations the au thors would then favor the hypothesis that, during pregnancy, the concentration of hypothalamic p-opioid receptors becomes more elevated because of the stressful conditions represented by pregnancy itself and by the oncoming delivery. Brain opioid peptides have been actually demonstrated to be significantly affected by stressful stimuli of various nature [27],…”

Section: Discussionmentioning

confidence: 99%

Hypothalamic Opiatergic Tone During Pregnancy, Parturition and Lactation in the Rat

et al. 1991

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The concentrations of β-endorphin have been shown to change in the rat brain during pregnancy and lactation. This study has been performed in order to analyze whether also brain opioid receptors might undergo significant modifications during these two physiological situations. The maximal binding capacity (B_max) and the constant of affinity (Ka) of the µ-subpopulation of opioid receptors have been evaluated in the hypothalami of female rats at different stages of pregnancy (7, 15 and 22 days), on the day of parturition (12–18 h after delivery) and 6–8 days postpartum (both in lactating and in nonlactating animals). Female rats killed on the day of estrus served as controls. The receptor binding assay has been performed utilizing [³H]-dihydromorphine ([³H]-DHM) as the ligand for the µ-opioid receptors. Hypothalamic concentrations of β-endorphin as well as serum levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin have also been evaluated by radioimmunoassay. The results showed that the concentration of hypothalamic µ-opioid receptors increased during pregnancy, being significantly higher than in the controls at days 15 and 22 of gestation. After delivery, the concentration of these receptors returned towards control values, regardless on whether the animals were lactating or not. The Ka values of [³H]-DHM for the µ-receptors did not change significantly in the different groups of experimental animals. Hypothalamic β-endorphin content showed a modest though not significant increase at the end of gestation (day 22) and returned to control values 12–18 h after delivery. During the postpartum period, a significant decrease in β-endorphin content was observed in lactating rats. LH and prolactin secretion underwent significant modifications throughout pregnancy and during the postpartum period. Serum LH levels were found to be low during the first part of gestation and to increase significantly on day 22; LH values returned to low levels 6–8 days after delivery both in lactating and in nonlactating animals. On the contrary, FSH secretion was not significantly affected during either pregnancy or the postpartum period. Serum prolactin levels were found to significantly increase on day 22 of pregnancy; after delivery, prolactin levels were elevated only in lactating rats. In conclusion, the present data clearly show that the concentration of µ-opioid receptors is significantly enhanced at the end of pregnancy, just before parturition occurs; this increase might be correlated to behavioral phenomena typical of this particular physiological condition (e.g. maternal pain perception). The results also show that the hypothalamic content of β-endorphin is decreased in the postpartum period, particularly in lactating rats; this decline might be important for the development of maternal behavior and for the control of the release of oxytocin, a hormone which is deeply involved in the mechanisms controlling lactation.

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“…These data suggest that these two chronic stressors, which are known to activate different central pathways and differently stimulate POMC-related peptides in anterior and intermediate lobes [20][21][22], have similar effects in reducing hypothalamic [1-EP content and abolishing its responsiveness to an acute challenge. The different central pathway activation linked to swimm ing or to ether stress is confirmed by the observation that GnRH contents are increased by the former model of stress, but not by the latter.…”

Section: Discussionmentioning

confidence: 81%

Effect of Different Chronic Intermittent Stressors and Acetyl-/-Carnitine on Hypothalamic β-Endorphin and GnRH and on Plasma Testosterone Levels in Male Rats

Bidzińska¹,

Angioni²,

Genazzani³

et al. 1993

Neuroendocrinology

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Chronic stress affects the reproductive function by modifying the neuroendocrine homeostasis. The aim of the present study was to clarify the neuroendocrine and the gonadal changes following chronic intermittent stress in male rats and the action of a neuroactive drug, acetyl-l-carnitine (ALC). The effect of two different stressors, cold water swimming or ether, on central β-endor-phin (β-EP) and GnRH contents, and on plasma testosterone levels was investigated. In addition, the response to an acute stress in chronically stressed rats, treated or untreated with ALC (10 mg/day/rat p.o.), was evaluated. The stressors were applied twice a day for 10 days, and rats were killed before, during and after the last stress session. Mediobasal hypothalamus (MBH) β-EP and GnRH contents, and plasma testosterone levels were evaluated by radioimmunoassay. The following results were obtained: (1) both chronic swimming and ether stress caused a decrease in hypothalamic β-EP contents; (2) MBH GnRH contents increased after chronic swimming stress but not after ether stress; (3) chronic swimming stress induced a twofold decrease in plasma testosterone levels, while no changes were observed after ether stress; (4) the treatment with ALC prevented the decrease in plasma testosterone levels after chronic swimming stress, and (5) acute stress in chronically stressed animals caused an increase in MBH β-EP. The present data showed that chronic swimming stress reduces the reproductive capacity and impairs the capacity to respond to the acute stress and that ALC modulates the hormonal changes to physical stress and prevents the antireproductive effect of chronic cold swimming.

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Stress-Induced Changes in Plasma, Pituitary and Hypothalamic Immunoreactive β-Endorphin: Effects of Diurnal Variation, Adrenalectomy, Corticosteroids, and Opiate Agonists and Antagonists

Cited by 68 publications

References 30 publications

Leu-Phe Cleaving Endopeptidase Activity, γ-Endorphin, and β-Endorphin in the Rat Pituitary Gland and Brain

Leu-Phe Cleaving Endopeptidase Activity, γ-Endorphin, and β-Endorphin in the Rat Pituitary Gland and Brain

Hypothalamic Opiatergic Tone During Pregnancy, Parturition and Lactation in the Rat

Effect of Different Chronic Intermittent Stressors and Acetyl-/-Carnitine on Hypothalamic β-Endorphin and GnRH and on Plasma Testosterone Levels in Male Rats

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