Journal of Neuroscience, Vol 7, 2564-2575, Copyright © 1987 by Society for Neuroscience
Selective cell death of magnocellular vasopressin neurons in neurohypophysectomized rats following chronic administration of vasopressin
JP Herman, FF Marciano, SJ Wiegand and DM Gash
Regeneration and functional recovery of the hypothalamoneurohypophysial
system (HNS) in neurohypophysectomized rats treated with either saline or
vasopressin (VP) were analyzed utilizing specific immunohistochemical and
physiological measures. Neural lobe ablation combined with VP
administration precipitated a profound diabetes insipidus (following
cessation of VP delivery) that persisted for the duration of the
experiment. Diabetes insipidus was correlated with a drastic reduction in
the number of VP-positive neurons in magnocellular hypothalamic nuclei. In
contrast, large numbers of oxytocin (OT)- positive neurons survived
neurohypophysectomy in VP-treated neurohypophysectomized rats; OT neurons
accounted for the vast majority of magnocellular profiles observed in
Nissl-counterstained sections. VP- immunoreactive fibers could be observed
in limited quantities in the external lamina of the median eminence of
VP-treated neurohypophysectomized rats, with little staining evident in the
internal lamina. Saline-treated neurohypophysectomized rats exhibited the
recovery of antidiuretic function characteristically seen following this
lesion, with evidence of survival of considerable numbers of VP and OT
neurons and median eminence hypertrophy. Both the internal and external
laminae of the median eminence were densely innervated by large-caliber VP
and OT fibers. Sham-operated animals receiving VP treatment did not show
any long-term deficit in water metabolism, changes in the complement of VP
or OT perikarya in hypothalamus, or changes in the innervation of the
median eminence. Results indicate that VP treatment following
neurohypophysectomy results in extensive retrograde degeneration of
magnocellular VP neurons without affecting the survival of OT cells.