Experimental Alterations of Endorphin Levels in Rat Pituitary

Baizman, Eugene R.; Cox, Brian M.; Osman, O.H.; Goldstein, A.

doi:10.1159/000122889

Cited by 64 publications

(13 citation statements)

References 32 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The temporal difference in the reduction of ir-pEP content found in AP and N-IL following foot shock supports previous observa tions [2] that ir-pEP content in these two tissues can be selec tively affected, and that the synthesis [27] and the release [32,37,38] of the peptide in AP and N-IL are affected by different factors. It is, however, not clear to what extent N-IL ir-PEP is released into the general circulation under basal or stressful conditions.…”

Section: Discussionsupporting

confidence: 87%

“…It is perhaps interesting that similar results for AP content of PEP have also been found by opiate re ceptor assay [2], suggesting that both P-LPH and p-EP are affected simultaneously by acute stress. The simplest expla nation for the changes of ir-PEP in AP is that foot shock en hances the release of ir-pEP from the AP into circulation at a rate exceeding its synthesis, leading eventually to a net de pletion of its content.…”

Section: Discussionsupporting

confidence: 70%

See 1 more Smart Citation

Foot Shock Analgesia

et al. 1982

View full text Add to dashboard Cite

Effects of inescapable foot shock on pain threshold and on levels of immunoreactive β-endorphin (ir-βEP) in anterior pituitary, neuro-intermediate lobe and plasma were determined by hot plate test and radioimmunoassay respectively. Whereas handling and conditioned stress failed to alter baseline pain threshold, 20 min inescapable foot shock produced modest and transient analgesia. Levels of plasma ir-βEP and corticosterone were significantly and concurrently raised by all treatments and remained elevated 40 min after foot shock. Changes in plasma levels of ir-βEP and corticosterone were found to parallel one another but did not correlate with changes in pain threshold. AP content of ir-βEP was significantly reduced 60 min after the cessation of inescapable foot shock, and N-IL content from 20 min after. The findings suggest that (i) plasma levels of ir-βEP and corticosterone do not reflect changes in pain threshold, and (ii) ir-βEP levels in anterior pituitary, neurointermediate lobe and plasma probably are not causally related to foot shock analgesia.

show abstract

Section: Discussionsupporting

confidence: 87%

Section: Discussionsupporting

confidence: 70%

Foot Shock Analgesia

et al. 1982

View full text Add to dashboard Cite

show abstract

“…Reduction in N-IL content of PEP and ACTH bio logical activities have been shown previously in rats subject ed to various stress procedures including immobilization [5], hypertonic saline ingestion [1,33] and breast feeding [1]. In electron microscopic studies [34], the reduction of ACTH in N-IL after immobilization has been shown to be consist ent with the depletion of secretory vesicles in the pituitary cells, suggesting significant excretion of the peptide.…”

Section: Discussionmentioning

confidence: 73%

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

Lim

Funder²

1983

Neuroendocrinology

View full text Add to dashboard Cite

Immunoreactive β-endorphin (ir-βEP) levels were determined in plasma, anterior pituitary (AP), neuro-intermediate lobe (N-IL) and hypothalamus (HT) of intact rats and adrenalectomized rats subjected to swimming stress. In intact rats, plasma ir-βEP was elevated fourfold, and ir-βEP levels in AP and N-IL significantly reduced after 30 min swimming; in contrast, HT ir-βEP in these animals was not affected. In adrenalectomized animals, similar but even more marked changes were found in plasma and tissue ir-βEP following stress. The effect of diurnal variation, morphine and naloxone on stress-induced changes in tissue ir-βEP was also examined; in addition, the influence of acute and chronic treatment of adrenalectomized animals with dexamethasone or deoxycorticosterone was explored. Plasma ir-βEP of rats swum in the afternoon was significantly higher than of those swum in the morning; no differences were detected in AP, N-IL or HT ir-βEP. Acute morphine administration (10 mg/kg) did not affect levels of ir-βEP in any tissue, baseline or post-stress; however, naloxone (10 mg/kg) consistently and significantly prevented the reduction in N-IL ir-βEP otherwise found following prolonged stress. Both acute and chronic dexamethasone (2 and 20 µg) attenuated the stress-induced changes found in AP and plasma ir-βEP in a dose-related manner; equivalent effects, however, were not seen in deoxycorticosterone (20, 200 µg) treated animals. In contrast, the stress-induced reduction found in N-IL ir-βEP was influenced neither by acute nor chronic treatment with dexamethasone or deoxycorticosterone. These results suggest that changes found in AP and plasma ir-βEP after swimming stress are glucocorticoid-sensitive, but do not involve pathways including opiate receptors; in contrast, though baseline levels of N-IL ir-βEP are mineralocorticoid-sensitive, the changes after swimming stress are steroid-independent and involve the action of endogenous opioids.

show abstract

“…A receptor-binding assay of morphine-like activity (MLA) was performed according to Baizman et al [1], A 2% rat brain homogen ate (prepared as described by Dr. B. Cox, personal commun.) was incubated at room temperature with 3H-etorphine (Amersham, TRK-476) in the presence of samples of perifusion medium or the naloxone-HCI standard (Endo Labs).…”

Section: Hormone Assaysmentioning

confidence: 99%

Differential Control of the Release of Pro-Opiomelanocortin-Derived Peptides from the Pars intermedia of the Rat Pituitary

Randle¹,

Moor²,

Kraicer³

1983

Neuroendocrinology

View full text Add to dashboard Cite

The pars intermedia (PI) of the adenohypophysis synthesizes pro-opiomelanocortin, which, through post-translational processing, gives rise to a group of chemically related peptides, including αMSH, ACTH, CLIP, LPHs and endorphins. We investigated the control of release of these peptides using an in vitro system. We perifused either acutely dispersed rat PI cells or intact neurointermediate lobes (NI). Perifusion medium and cell extracts were subjected to a series of bioassays (BA) and radioimmunoassays (RIA) (including MSH-BA, αMSH-RIA, ACTH-BA, ACTH-RIA, LPH-RIA) and a receptor-binding assay for morphine-like activity (MLA). The relative amounts of release of the various peptide activities was examined under basal and stimulated conditions. Under basal conditions, intact NI released approximately equal amounts of αMSH immunoactivity, MSH bioactivity and MLA, slightly less ACTH and LPH immunoactivity and far less ACTH bioactivity. Relative to αMSH immunoactivity, the rate of release of ACTH bioactivity decreased in the course of an experiment while the release of the other peptide activities increased. The peptide activities were released from dispersed PI cells in relative amounts similar to those from intact NI. The relative amounts of peptide activities contained in extracts of dispersed PI cells differed from the amounts released such that when compared to αMSH immunoactivity, the release of LPH and ACTH immunoactivities and MLA is 3–4 times greater while the release of ACTH bioactivity is one-half. Serotonin (10^–7–10^–5M) markedly stimulated the release of ACTH bioactivity from both dispersed PI cells and intact NI in a dose-related manner. Serotonin had a smaller stimulatory effect on the release of αMSH and LPH immunoactivity but had no effect on the release of MLA and ACTH immunoactivity. These observations indicate that there is differential control of the release of POMC-derived peptides from the rat PI.

show abstract

Experimental Alterations of Endorphin Levels in Rat Pituitary

Cited by 64 publications

References 32 publications

Foot Shock Analgesia

Foot Shock Analgesia

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

Differential Control of the Release of Pro-Opiomelanocortin-Derived Peptides from the Pars intermedia of the Rat Pituitary

Contact Info

Product

Resources

About