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Coexpression of dynorphin and neurokinin B immunoreactivity in the rat hypothalamus: Morphologic evidence of interrelated function within the arcuate nucleus
Author(s) -
Burke Michelle C.,
Letts Penny A.,
Krajewski Sally J.,
Rance Naomi E.
Publication year - 2006
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.21086
Subject(s) - dynorphin , arcuate nucleus , hypothalamus , medicine , nucleus , stria terminalis , biology , median eminence , endocrinology , neurokinin b , neuropeptide , neuroscience , receptor , opioid peptide , substance p , opioid
Considerable evidence suggests that dynorphin and neurokinin B (NKB) neurons in the hypothalamic arcuate nucleus participate in the sex‐steroid regulation of reproduction. In the present study, we used dual‐label immunofluorescence to explore the distribution of prodynorphin and proNKB immunoreactivity in the rat hypothalamus. Additionally, we investigated whether arcuate prodynorphin‐ir (immunoreactive) neurons expressed the neurokinin 3 receptor (NK 3 R) or nuclear estrogen receptor‐α (ERα). We found that the majority of prodynorphin‐ir neurons in the rat arcuate nucleus expressed proNKB, whereas nearly all (99%) of the proNKB neurons were immunoreactive for prodynorphin. The arcuate nucleus was the only site in the hypothalamus where neuronal somata coexpressing prodynorphin and proNKB‐immunoreactivity were identified. A dense plexus of double‐labeled prodynorphin/proNKB‐ir fibers was found within the arcuate nucleus extending to the median eminence and throughout the periventricular zone of the hypothalamus. Prodynorphin/proNKB fibers were also identified in the paraventricular nucleus, anterior hypothalamic area, medial preoptic area, median preoptic nucleus, anteroventral periventricular nucleus, and bed nucleus of the stria terminalis in a distribution consistent with previously described arcuate nucleus projections. Interestingly, the majority of prodynorphin‐ir neurons in the arcuate nucleus expressed NK 3 R, and nearly 100% of the prodynorphin‐ir neurons contained nuclear ERα. Our results suggest that there is a close functional relationship between dynorphin and NKB peptides within the arcuate nucleus of the rat, which may include an autofeedback loop mediated through NK 3 R. The diverse hypothalamic projections of fibers expressing both prodynorphin and proNKB provide evidence that these neurons may participate in a variety of homeostatic and neuroendocrine processes. J. Comp. Neurol. 498:712–726, 2006. © 2006 Wiley‐Liss, Inc.