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Abstract
Neuropeptide Y, produced in the arcuate nucleus of the hypothalamus, plays a key role
in the central regulation of anterior pituitary and appetitive functions. The pleiotropic
nature of neuropeptide Y in these mechanisms indicates the existence of heterogeneity
in the hypothalamic neuronal population producing neuropeptide Y. In this study, we
report the coexistence of neuropeptide Y and the amino acid transmitter, gamma-aminobutyric
acid (GABA), in neuronal perikarya of the arcuate nucleus. Fluorescent double immunolabeling
for neuropeptide Y and glutamic acid decarboxylase was carried out on vibratome sections
collected through the hypothalamic arcuate nuclei of animals that were pretreated
with colchicine. It was found that about one third of the neuropeptide Y-producing
arcuate nucleus perikarya co-expressed glutamic acid decarboxylase. This population
of neuropeptide Y-containing GABAergic neurons were distributed longitudinally within
the arcuate nucleus located predominantly in its dorsomedial aspects. These results
show that there are at least two distinct populations of neuropeptide Y-producing
neurons in the arcuate nucleus: a subset of neuropeptide Y and GABA-co-producing neurons
located in the dorsomedial arcuate nucleus and a subset of non-GABAergic neuropeptide
Y cells located in the ventral arcuate nucleus. This heterogeneity in the neuropeptide
Y-producing perikarya of the hypothalamus may help explain adverse neuroendocrine
and behavioral effects of arcuate nucleus neuropeptide Y.