Adrenergic regulation of hypothalamic proenkephalin neurons: evidence for opposite effects in subpopulations terminating in median eminence and neurointermediate pituitary.
The effect of adrenergic influences on Met-enkephalin concentrations in median eminence, neurointermediate pituitary and hypothalamus outside median eminence were examined. Met-enkephalin levels in median eminence were augmented by administration of the alpha 1-adrenergic agonist methoxamine acutely or chronically and decreased by the selective depletion of adrenergic transmitters by 6-hydroxydopamine. Met-enkephalin levels in neurointermediate lobe were decreased by methoxamine but unaffected by depletion of noradrenaline/adrenaline. These results indicate that adrenergic mechanisms maintain Met-enkephalin concentrations tonically in median eminence and deplete Met-enkephalin concentrations in neurointermediate lobe. These results suggest differential adrenergic regulation of hypothalamic proenkephalin neurons terminating in median eminence and neural lobe of pituitary.
George
S R
SR
Department of Medicine, University of Toronto, Canada.
Roldan
L
L
Haas
D A
DA
D000818:Animals; D004744:Enkephalin, Methionine / Q000302:isolation & purification / Q000378:metabolism; D004745:Enkephalins / Q000502:physiology*; D006892:Hydroxydopamines / Q000494:pharmacology; D007031:Hypothalamus / Q000166:cytology / Q000502:physiology*; D066298:In Vitro Techniques; D008297:Male; D008473:Median Eminence / Q000502:physiology*; D008729:Methoxamine / Q000494:pharmacology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000502:physiology*; D016627:Oxidopamine; D010904:Pituitary Gland, Posterior / Q000502:physiology*; D011498:Protein Precursors / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012110:Reserpine / Q000494:pharmacology; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*
D004745:Enkephalins; D006892:Hydroxydopamines; D011498:Protein Precursors; C029992:proenkephalin; D004744:Enkephalin, Methionine; D012110:Reserpine; D016627:Oxidopamine; D008729:Methoxamine