Effects of different opiate agonists on melanocyte-stimulating hormone release: <i>in vivo</i> and <i>in vitro</i> studies

The effects of acute injections of synthetic opiate peptides into the lateral cerebral ventricle of young adult male rats on cells of the intermediate lobe of the pituitary were studied. Met-enkephalin (100/micrograms) injected into anesthetized rats, or 20 micrograms beta-endorphin administered via a previously implanted cannula to unanesthetized animals, will lead to cell degranulation and often to expanded Golgi zones and prominent regions of rough endoplasmic reticulum in secretory cells when tissue is fixed 45--60 min after peptide administration. Treatment of animals with the opiate antagonist naloxone hydrochloride prior to enkephalin injection appeared to prevent the cellular changes elicited with peptide alone. Observations suggest that opiate peptides administered to the cerebrospinal fluid may stimulate release of pro-opiomelanocortin-peptide from pituitary cells.

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Methionine enkephalin-induced changes in pigmentation of zebrafish (cyprinidae, Brachydanio rerio) and related species and varieties, measured videodensitometrically

Zebrafish¹,

Levina²,

Gordon³

1983

General and Comparative Endocrinology

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The ability of MSH and of methionine enkephalin (met-E) to induce dispersion of pigment granules was examined in melanophores and in xanthophores of the zebrafish Brachydanio rerio using the melanophore index (MI) and videodensitometry. Both methods gave similar results. In B. rerio both MSH and met-E induced pigment dispersion in dermal melanophores, in fin and peritoneal melanophores, and in xanthophores. Darkening lasted a few hours. However, met-E-induced darkening developed 40-50 min later and faded more slowly than the effect of MSH. Both effects were dose related. Naloxone prevented met-E-induced darkening while it did not interfere with the MSH-induced effect. Epidermal melanophores did not react to either MSH or met-E. Thus met-E proved to induce changes of coloration when injected into a fish. Our data suggest a central mechanism involved in met-E-mediated change of coloration in zebrafish under the conditions examined. A new approach was suggested for objective measurement of the mean body darkness of the fish with the help of computational videodensitometry. Our fist results indicate a proportionality between the MI evaluation and videodensitometry.

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Effects of different opiate agonists on melanocyte-stimulating hormone release: in vivo and in vitro studies

Cited by 15 publications

References 1 publication

Endogenous Peptides in Circulatory Shock

Endogenous Peptides in Circulatory Shock

Effects of acute opiate-peptide administration on pro-opiomelanocortin cells of the intermediate lobe of the rat pituitary

Methionine enkephalin-induced changes in pigmentation of zebrafish (cyprinidae, Brachydanio rerio) and related species and varieties, measured videodensitometrically

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