Neurokinin B- and kisspeptin-positive fibers as well as tuberoinfundibular dopaminergic neurons directly innervate periventricular hypophyseal dopaminergic neurons in rats and mice

Nobuhiko Sawai
Norio Iijima
Hitoshi Ozawa
Toshiyuki Matsuzaki

Neurons co-expressing kisspeptin
 neurokinin B (NKB)
 and dynorphin in the hypothalamic arcuate nucleus
 named KNDy neurons
 are directly affected by sex hormones
 and are well known for regulating the secretion of gonadotropin-releasing hormone. However
 recent studies have shown that KNDy neurons also project and terminate to tuberoinfundibular dopaminergic (TIDA) neurons
 suggesting a role in prolactin secretion. Moreover
 there is a possibility that other neurosecretory dopaminergic neurons regulating prolactin secretion
 such as periventricular hypophyseal dopaminergic (PHDA) neurons
 may also be innervated by KNDy neurons. In the present study
 by means of double immunohistochemistry and retrograde neural tracer
 we examined whether KNDy neurons project directly to PHDA neurons that project to blood vessels
 as well as to TIDA neurons. The results revealed that KNDy neurons are widely projecting to neurosecretory dopaminergic neurons of the PHDA and TIDA neurons in rats and mice. Secondary
 presence of a major receptor for NKB
 neurokinin-3 receptor (NK3R)
 in PHDA and TIDA neurons was examined and it appeared that most TIDA and PHDA neurons possess NK3R. These findings indicate that
 in rodents
 KNDy neurons widely project to neurosecretory dopaminergic neurons distributed in the hypothalamus
 and may affect them via the NKB-NK3R signaling pathway. (C) 2014 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

NEUROSCIENCE RESEARCH

ELSEVIER IRELAND LTD

84

10.1016/j.neures.2014.05.002

https://doi.org/10.1016/j.neures.2014.05.002
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