Stress, dopaminergic blockade and median eminence-neurointermediate lobe catecholamine depletion: effects on hypothalamic, pituitary and plasma immunoreactive beta-endorphin.
We have compared immunoreactive beta-endorphin (ir-beta EP) levels in plasma, hypothalamus, anterior pituitary and neurointermediate lobe of adult female Sprague-Dawley rats, in studies in which levels of catecholamines were manipulated. Whole-brain catecholamines were manipulated by intraperitoneal haloperidol and/or bromocriptine; median eminence and neurointermediate lobe catecholamines were manipulated specifically and differentially by intravenous 6-hydroxydopamine (6-OHDA), with and without pretreatment with intraperitoneal desipramine; changes in amine neurons were assessed by fluorescence histochemistry. Haloperidol and 6-OHDA administration produced a selective reduction of neurointermediate lobe ir-beta EP, to levels equivalent to those seen with prolonged stress; the haloperidol effect was blocked by bromocriptine and the 6-OHDA effect by desipramine. Specific depletion of catecholamine nerve terminals in the median eminence and the neurointermediate lobe was associated with elevated plasma ir-beta EP, with no changes in pituitary or hypothalamic levels. These studies confirm and extend previous reports documenting that ir-beta EP levels in different tissues are modulated by different neural stimuli.
D000818:Animals; D002395:Catecholamines / Q000502:physiology*; D003891:Desipramine / Q000494:pharmacology; D018492:Dopamine Antagonists; D004723:Endorphins / Q000032:analysis*; D005260:Female; D006220:Haloperidol / Q000494:pharmacology; D006892:Hydroxydopamines / Q000494:pharmacology; D007031:Hypothalamus / Q000032:analysis; D008473:Median Eminence / Q000502:physiology*; D016627:Oxidopamine; D010902:Pituitary Gland / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D013312:Stress, Physiological / Q000378:metabolism*; D013550:Swimming; D001615:beta-Endorphin
D002395:Catecholamines; D018492:Dopamine Antagonists; D004723:Endorphins; D006892:Hydroxydopamines; D001615:beta-Endorphin; D016627:Oxidopamine; D006220:Haloperidol; D003891:Desipramine