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Simultaneous changes in hypothalamic catecholamine levels and plasma corticosterone concentration in the rat after acute morphine and during tolerance.

M V Milanés·M M Puig·M L Vargas
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Abstract

The effects of morphine on plasma corticosterone and hypothalamic noradrenaline (NA) and dopamine (DA) content were studied in naive and in morphine-tolerant rats. Acutely administered morphine (30 mg/kg i.p.) significantly increased the plasma levels of corticosterone and significantly reduced the hypothalamic NA and DA content. In chronically morphine-treated rats (subcutaneously implanted with pellets for 7 days), a challenge dose of morphine (30 mg/kg intraperitoneally (i.p.)) did not modify the plasma corticosterone levels and inhibited the morphine-induced decreases in hypothalamic NA and DA content. These results suggest that: (1) In naive rats, the morphine-induced activation of hypothalamus-pituitary-adrenocortical (HPA) axis is mediated by catecholaminergic neurons in the hypothalamus; (2) In tolerant rats morphine did not modify the plasma corticosterone concentrations, presumably by attenuating hypothalamic noradrenergic and dopaminergic activity. (3) Hypothalamic catecholamines have a role in regulating the HPA axis during morphine tolerance.

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AnimalsCorticosteroneDopamineDrug Administration ScheduleDrug ToleranceEndorphinsHypothalamo-Hypophyseal SystemHypothalamusMaleMorphineNeuronsNorepinephrinePituitary-Adrenal SystemRatsRats, Sprague-DawleyComparative StudyJournal ArticleResearch Support, Non-U.S. Gov't

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M V Milanés, M M Puig, M L Vargas. 1993. Simultaneous changes in hypothalamic catecholamine levels and plasma corticosterone concentration in the rat after acute morphine and during tolerance.. https://doi.org/10.1016/0143-4179(93)90016-4

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