Neurochemical Research

, Volume 9, Issue 2, pp 207–217 | Cite as

Naltrexone effects on pituitary neurointermediate lobe and median eminence

  • L. C. Saland
  • E. Reyes
  • E. Ortiz
Original Articles


The long-acting opiate antagonist naltrexone hydrochloride was administered by intraperitoneal injection, in a dose response protocol, to adult rats. The drug was used to observe effects of opiate receptor blockade on cells of the pituitary gland and adjacent hypothalamus. At higher drug doses (5mg/kg or 10mg/kg), neurites directly innervating pars intermedia cells contained swollen vesicles and disrupted membranous elements. Fibers within the median eminence of the hypothalamus appeared swollen, and contained myelin figures. Despite the consistent degenerative changes appearing in neurites, measurements of levels of dopamine, norepinephrine, and epinephrine in striatum, and hypothalamus did not differ significantly between naltrexone-treated or control animals, although there was a significant elevation of norepinephrine in the pituitary after drug treatment. At all drug dose levels administered, supraependymal neuron-like cells appeared atop the ependyma of the third ventricle above the median eminence. These observations suggest that naltrexone produces specific “neurotoxic” effects on neurites of the tuberoinfundibular system, and may induce changes in the ventricular environment which stimulate the appearance of supraependymal neurons.


Naltrexone Median Eminence Opiate Receptor Membranous Element Opiate Antagonist 
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Copyright information

© Plenum Publishing Corporation 1984

Authors and Affiliations

  • L. C. Saland
  • E. Reyes
    • 1
  • E. Ortiz
  1. 1.Departments of Anatomy and PharmacologyUniversity of New Mexico School of MedicineAlbuquerque

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