SUBTYPES Y1 AND Y2 OF THE NEUROPEPTIDE-Y RECEPTOR ARE RESPECTIVELY EXPRESSED IN PRO-OPIOMELANOCORTIN-CONTAINING AND NEUROPEPTIDE-Y-CONTAINING NEURONS OF THE RAT HYPOTHALAMIC ARCUATE NUCLEUS
C. Broberger et al., SUBTYPES Y1 AND Y2 OF THE NEUROPEPTIDE-Y RECEPTOR ARE RESPECTIVELY EXPRESSED IN PRO-OPIOMELANOCORTIN-CONTAINING AND NEUROPEPTIDE-Y-CONTAINING NEURONS OF THE RAT HYPOTHALAMIC ARCUATE NUCLEUS, Neuroendocrinology, 66(6), 1997, pp. 393-408
The arcuate nucleus of the hypothalamus houses a number of neurochemic
ally different cell populations. Among these, a dense cluster of small
neuropeptide-Y (NPY)-expressing neurons is located in its ventromedia
l subdivision and a pro-opiomelanocortin (POMC)-expressing neuron popu
lation in its ventrolateral part. Furthermore, both neuropeptide Y Y1
and Y2 receptors (Y1-Rs and Y2-Rs) are expressed in the arcuate nucleu
s. Here we analyse the co-expression of NPY and POMC/adrenocorticotrop
ic hormone with the Y1-R and Y2-R in arcuate neurons using immunohisto
chemistry and in situ hybridization. Many, but not all, POMC neurons e
xpressed Y1-R mRNA and protein. Conversely, several Y1-R-positive, POM
C-negative neurons were found. NPY-positive nerve terminals were found
in close apposition to Y1-R-like immunoreactivity localized close to
the dendritic and somatic cell membranes. Y2-R mRNA was found in almos
t all NPY mRNA-expressing neurons, but also in a group of NPY mRNA-neg
ative cells. These results show that the POMC neurons are targets for
NPY, which is presumably present in, and released from, fibres origina
ting in the ventromedial arcuate nucleus and which may play a role in
NPY-induced feeding. Release of NPY, and possible coexisting messenger
s, may be controlled by presynaptic Y2-R expressed in NPY neurons. Tak
en together, the findings support the division of Y1-Rs and Y2-Rs into
post- and presynaptic receptors, respectively.