Journal of Neuroscience, Vol 13, 1138-1147, Copyright © 1993 by Society for Neuroscience
Neuropeptide Y mRNA and immunoreactivity in hypothalamic neuroendocrine neurons: effects of adrenalectomy and chronic osmotic stimulation
PJ Larsen, JD Mikkelsen, DS Jessop, SL Lightman and HS Chowdrey
Institute of Medical Anatomy, Department B, University of Copenhagen, Denmark.
Neuropeptide Y (NPY) coexists with vasopressin or oxytocin in magnocellular
neurons of the hypothalamo-neurohypophysial tract. Using quantitative in
situ hybridization histochemistry and immunohistochemistry, we have studied
the effects of adrenalectomy and chronic osmotic stimulation, either alone
or in combination, on NPY mRNA expression and NPY immunoreactivity in
magnocellular neurons of the hypothalamic paraventricular (PVN) and
supraoptic (SON) nuclei, and arcuate nucleus (Arc). Adrenalectomy and
chronic osmotic stimulation each increased NPY mRNA levels in magnocellular
neurons of the PVN and SON, while the combination of both treatments had an
additive effect. In the Arc, only the combination of adrenalectomy and
chronic osmotic stimulation increased NPY mRNA levels. Chronic osmotic
stimulation also resulted in a marked increase of NPY-immunoreactive
magnocellular perikarya in the PVN and SON. In contrast, adrenalectomy had
only minor effects on the number of NPY-immunoreactive magnocellular
PVN/SON perikarya. Neither chronic osmotic stimulation nor adrenalectomy
affected the number of NPY-immunoreactive Arc perikarya. However,
adrenalectomy decreased the number of NPY-immunoreactive nerve terminals in
the external zone of the median eminence, while chronic osmotic stimulation
increased the number of immunoreactive nerve fibers in the internal zone of
the median eminence. The present study provides evidence that adrenalectomy
and chronic osmotic stimulation can separately influence NPY gene
transcription in magnocellular hypothalamo-neurohypophysial neurons, while
only the combined effect of adrenalectomy and chronic osmotic stimulation
increases NPY mRNA expression in neurons of the Arc.