The Journal of Neuroscience, August 15, 1999, 19(16):7130-7139
Changes in Neuropeptide Y Receptors and Pro-Opiomelanocortin in
the Anorexia (anx/anx) Mouse Hypothalamus
Christian
Broberger1,
Jeanette
Johansen2,
Hjalmar
Brismar3,
Carolina
Johansson2,
Martin
Schalling2, and
Tomas
Hökfelt1
Departments of 1 Neuroscience, 2 Molecular
Medicine, and 3 Woman and Child Health, Karolinska
Institutet, 171 77 Stockholm, Sweden
The pro-opiomelanocortinergic (POMCergic) system originating in the
hypothalamic arcuate nucleus extends projections widely over the brain
and has been shown to be intricately linked and parallel to the arcuate
neuropeptide Y (NPY) system. Both NPY and POMC-derived peptides
(melanocortins) have been strongly implicated in the control of feeding
behavior, with the former exerting orexigenic effects and the latter
having anorexigenic properties. Mice homozygous for the lethal anorexia
(anx) mutation are hypophagic, emaciated, and exhibit
anomalous processing of NPY exclusively in the arcuate nucleus,
providing an interesting model to study NPY-POMC interactions. In the
present study, several morphological markers were used to investigate
the histochemistry and morphology of the POMC system in
anx/anx mice. In situ
hybridization demonstrated decreased numbers of POMC mRNA-expressing
neurons in the anx/anx arcuate nucleus. In parallel,
mRNA levels for both the NPY Y1 and Y5 receptors, which are expressed
in POMC neurons, were decreased. Also, expression of the NPY Y2
autoreceptor was attenuated. Immunohistochemistry using antibodies
against adrenocorticotropic hormone to demonstrate POMC cell bodies,
against
-melanocyte-stimulating hormone to demonstrate axonal
projections and against the NPY Y1 receptor to demonstrate dendritic
arborizations, showed strikingly decreased immunoreactivities for all
these markers. The present data suggest that degeneration of the
arcuate POMC system is a feature characteristic of the
anx/anx mouse. The possible relationship
to the NPYergic phenotype of this animal is discussed.
Key words:
adrenocorticotropic hormone;
-melanocyte-stimulating hormone; arcuate nucleus; feeding; immunohistochemistry; in situ hybridization; paraventricular nucleus of the hypothalamus; trophism
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