title: Simultaneous changes in hypothalamic catecholamine levels and plasma corticosterone concentration in the rat after acute morphine and during tolerance.
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.
authors.affiliation: Department of Physiology and Pharmacology, University School of Medicine, Muricia, Spain.
authors.forename: M V
authors.initials: MV
authors.lastname: Milanés
authors.forename: M M
authors.initials: MM
authors.lastname: Puig
authors.forename: M L
authors.initials: ML
authors.lastname: Vargas
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000097:blood*; D004298:Dopamine / Q000378:metabolism*; D004334:Drug Administration Schedule; D004361:Drug Tolerance; D004723:Endorphins / Q000502:physiology; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects* / Q000378:metabolism; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000494:pharmacology*; D009474:Neurons / Q000378:metabolism; D009638:Norepinephrine / Q000378:metabolism*; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D004723:Endorphins; D009020:Morphine; D004298:Dopamine; D003345:Corticosterone; D009638:Norepinephrine